Catalysts 2013, 3(4), 839-852; doi:10.3390/catal3040839

Article
Palladium-Catalyzed Polyfluorophenylation of Porphyrins with Bis(polyfluorophenyl)zinc Reagents
Noriaki Sugita , Satoshi Hayashi , Sawa Ishii and Toshikatsu Takanami *
Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose, Tokyo 204-8588, Japan; E-Mails: d136901@std.my-pharm.ac.jp (N.S.); shayashi@my-pharm.ac.jp (S.H.); m136203@std.my-pharm.ac.jp (S.I.)
*
Author to whom correspondence should be addressed; E-Mail: takanami@my-pharm.ac.jp; Tel.: +81-42-495-8780; Fax: +81-42-495-8779.
Received: 9 August 2013; in revised form: 25 September 2013 / Accepted: 8 October 2013 /
Published: 22 October 2013

Abstract

: A facile and efficient method for the synthesis of pentafluorophenyl- and related polyfluorophenyl-substituted porphyrins has been achieved via palladium-catalyzed cross-coupling reactions of brominated porphyrins with bis(polyfluorophenyl)zinc reagents. The reaction is applicable to a variety of free-base bromoporphyrins, their metal complexes, and a number of bis(polyfluorophenyl)zinc reagents.
Keywords:
porphyrin; polyfluorophenylation; bis(polyfluorophenyl)zinc; palladium; cross-coupling

1. Introduction

The construction of porphyrins and related tetrapyrrolic macrocycles has attracted much interest [1,2,3,4,5,6] because they have a variety of important applications in many fields [7,8], including catalysis [9,10,11,12,13,14], medicine [15,16,17,18], and materials [19,20,21,22,23,24,25,26,27]. It is also well documented that the chemical, physical, and biological properties of porphyrin macrocycles can be systematically tuned by the electronic, steric and conformational environments of their peripheral substituents [7,8]. Penta-fluoro-phenyl and related polyfluorophenyl groups are one of the most important peripheral substituents in that their strong electron-withdrawing nature can greatly affect the electronic properties of a porphyrin core [25,27]. Conventional approaches to synthesizing pentafluorophenyl-substituted porphyrins involve multiple condensation reactions of pentafluorobenzaldehydes by using various monopyrroles or substituted dipyrromethanes under acidic conditions, followed by oxidation of the resulting porphyrinogen intermediates [26,27,28,29,30]. However, these multiple-condensation methods have low yields, significant side products, and difficult purifications. Palladium and related transition metal-catalyzed cross-couplings of polyfluoroarenes with aryl halides [31,32,33,34] would facilitate alternative synthetic pathways to pentafluorophenyl-substituted porphyrins. However, to our knowledge, only one report to date, by Therien et al. [35], evaluates such palladium-catalyzed methods for preparing pentafluorophenyl-substituted porphyrins. They used Pd(dppf) as the catalyst and investigated couplings of C6F5ZnCl by using only two examples of zinc complexes of bromoporphyrins, [2-bromo-5,10,15,20-tetraphenylporphinato]zinc(II) and [5,15-dibromo-10,20-diphenylporphinato]zinc(II), as the substrates; however, no further reports have alluded to any extension of this methodology [35].

We wanted to investigate whether this protocol could be extended to other bromoporphyrins, particularly those of free bases. We report herein a general method for synthesizing polyfluorophenyl-substituted porphyrins from the corresponding bromoporphyrins utilizing bis(polyfluorophenyl)zinc reagents as the coupling partner and Pd(OAc)2/t-Bu3P as the catalyst system. The present catalytic protocol can be carried out in high yields under mild conditions and can easily be applied to a variety of bromoporphyrins, such as meso-mono-, meso-di-, and β-mono-bromoporphyrins, enabling the synthesis not only of meso- and β-mono-polyfluorophenylated porphyrins but also of meso-bis(poly-fluorophenyl)-substituted derivatives.

2. Results and Discussion

At the outset of our work, we examined the catalytic pentafluorophenylation of 5,15-diphenyl­porphyrin 1a with C6F5ZnCl in accordance with the method developed by Therien et al. [35]. We thus achieved coupling of porphyrin 1a with the organozinc reagent in the presence of Pd(dppf)Cl2 (5 mol%) as a catalyst in THF at 25 °C and 60 °C (Table 1, entries 1 and 2). However, unfortunately, we did not obtain the desired fluorinated product Zn-2a after 20 h. Instead, the reactions produced zinc complexes of the starting bromoporphyrin Zn-1a as undesired byproducts in quantitative yields. Despite these disappointing results, we continued our investigation by changing the C6F5 source from C6F5ZnCl to commercially available (C6F5)2Zn, and we were pleased to obtain the desired product Zn-2a in 12% yield (Table 1, entry 3).

Encouraged by this result, a series of palladium catalysts, ligands, and solvents were investigated to identify the variable(s) that affect the yield of the pentafluorophenylation product in the coupling reaction of the free-base meso-bromoporphyrin 1a with the organozinc reagent (C6F5)2Zn. As shown in Table 2, most of the palladium tertiary phosphine complexes we examined, either generated in situ or preformed, were ineffective for the coupling reaction, affording only low yields of the desired fluorinated product Zn-2a and the zinc complex of the starting bromoporphyrin Zn-1a. However, use of an electron-rich bulky monophosphine ligand, t-Bu3P, can effectively catalyze the reaction in combination with both palladium complexes, Pd(dba)2 and Pd(OAc)2 (entries 9 and 14). We selected Pd(OAc)2 as the palladium catalyst of choice for further investigation because of its high catalytic activity and low cost. A brief investigation of solvents found that ethereal solvents, such as THF and dioxane, were suitable reaction media (entries 14–17). Among which, THF was the solvent of choice in terms of yield of the desired fluorinated product Zn-2a (entry 14). Nonpolar solvent such as toluene did not promote the coupling reaction and gave no desired product (entry 17). Thus, with respect to optimized conditions the reaction of 1a with 5 equiv of (C6F5)2Zn in the presence of 5 mol% Pd(OAc)2 and 10 mol% t-Bu3P·HBF4 in THF at 60 °C afforded pentafluorophenyl-substituted product Zn-2a in 95% yield within 3 h (entry 14).

Table 1. Palladium-catalyzed coupling of free-base bromoporphyrin 1a with pentafluorophenylzinc reagents, C6F5ZnCl and (C6F5)2Zn.

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Table 1. Palladium-catalyzed coupling of free-base bromoporphyrin 1a with pentafluorophenylzinc reagents, C6F5ZnCl and (C6F5)2Zn.
Catalysts 03 00839 i001
EntryC6F5 sourceTemp. (°C)Yield a (%) of Zn-2aYield a (%) of Zn-1a
1C6F5ZnCl250>99
2C6F5ZnCl60trace95
3(C6F5)2Znb601284

a Isolated yield. b Using 5 equiv of (C6F5)2Zn.

Table 2. Screening of palladium catalyst for coupling of meso-bromoporphyrin 1a with bis(pentafluorophenyl)zinc.

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Table 2. Screening of palladium catalyst for coupling of meso-bromoporphyrin 1a with bis(pentafluorophenyl)zinc.
Catalysts 03 00839 i002
EntryPd sourceLigandSolvent/tempt (h)Yield a (%) of Zn-2aYield a (%) of Zn-1a
1Pd(dppf)Cl2b-THF/60 °C121284
2Pd(Ph3P)2Cl2- 200>99
3Pd(Ph3P)4- 122369
4Pd(dppe)2c- 200>99
5Pd(dba)2dppfTHF/60 °C121482
6 Ph3P 101083
7 Cy3P 102374
8 SPhosd 20trace95
9 t-Bu3P·HBF4 3940
10Pd(OAc)2dppfTHF/60 °C18trace97
11 Ph3P 121185
12 Cy3P 121877
13 SPhos 200>99
14 t-Bu3P·HBF4 3950
15Pd(OAc)2t-Bu3P·HBF4dioxane/60 °C3890
16 dioxane/95 °C2920
17 toluene/110 °C200>99

a Isolated yield.

Having identified optimized conditions for the pentafluorophenylation of porphyrins, we explored the substrate scope of this process by using (C6F5)2Zn (Table 3). These conditions were compatible with various phenyl substituents, including alkyl, alkoxy, alkenyl, and alkynyl groups on the meso-brominated free-base diarylporphyrins, and we obtained the corresponding pentafluorophenyl-substituted zinc complexes in high yields (entries 1–6). Other free bases, including 10,20-dialkyl- and 10,15,20-trisubstituted bromoporphyrins, also participated in the catalytic pentafluorophenylation (entries 7 and 8). Central metal ions, such as Zn and Ni, could be incorporated into the products without greatly affecting the efficiency of the pentafluorophenylation (entries 9 and 10). Furthermore, we successfully employed β-bromoporphyrin 1i, affording the desired β-pentafluorophenyl-substituted product Zn-2i in 92% yield (Scheme 1). The reaction also occurred with dibromoporphyrin 1j to provide porphyrin Zn-2j, which contained two pentafluorophenyl substituents at the meso positions, in 86% yield (Scheme 2).

Table 3. Palladium-catalyzed coupling of bis(pentafluorophenyl)zinc with various bromoporphyrins.

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Table 3. Palladium-catalyzed coupling of bis(pentafluorophenyl)zinc with various bromoporphyrins.
Catalysts 03 00839 i003
EntryR1R2M1M2SubstrateProductt (h)Yield a (%)
1PhH2HZn1aZn-2a395
2p-tolylH2HZn1bZn-2b493
33-(CH2=CH)C6H4H2HZn1cZn-2c488
44-(i-Pr3SiC≡C)C6H4H2HZn1dZn-2d297
52,4,6-Me3C6H2H2HZn1eZn-2e490
63-(MeO)C6H4H2HZn1fZn-2f489
7i-BuH2HZn1gZn-2g394
8PhPh2HZn1hZn-2h396
9PhHZnZnZn-1aZn-2a199
10PhHNiNiNi-1aNi-2a197

a Isolated yield.

Catalysts 03 00839 g001 200
Scheme 1. Preparation of β-pentafluorophenyl-substituted porphyrin Zn-2i.

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Scheme 1. Preparation of β-pentafluorophenyl-substituted porphyrin Zn-2i.
Catalysts 03 00839 g001 1024
Catalysts 03 00839 g002 200
Scheme 2. Preparation of bis(pentafluorophenyl)porphyrin Zn-2j.

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Scheme 2. Preparation of bis(pentafluorophenyl)porphyrin Zn-2j.
Catalysts 03 00839 g002 1024
Table 4. Palladium-catalyzed coupling of 1a with various bis(polyfluorophenyl)zinc reagents.

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Table 4. Palladium-catalyzed coupling of 1a with various bis(polyfluorophenyl)zinc reagents.
Catalysts 03 00839 i004
Entry(FnAr)2ZnProductt (h)Yield a (%)
1 Catalysts 03 00839 i005Zn-2a395
2 Catalysts 03 00839 i006Zn-3396
3 Catalysts 03 00839 i007Zn-4298
4 Catalysts 03 00839 i008Zn-5293
5 Catalysts 03 00839 i009Zn-6195
6 Catalysts 03 00839 i010Zn-71270

a Isolated yield.

We next investigated the scope of bis(polyfluorophenyl)zinc reagents, which can readily be prepared in situ from the corresponding polyfluorophenyl Grignard reagents and Zn(OMe)2 in THF, by using meso-bromoporphyrin 1a, as depicted in Table 4. In addition to standard pentafluorophenylation with (C6F5)2Zn, related zinc reagents possessing 2,3,5,6-tetrafluoro-, 3,4,5-trifluoro-, and 3,6-difluoro-phenyl groups reacted to produce the corresponding polyfluorophenyl-substituted products in high yields (entries 1–4). An alkoxy-substituted zinc reagent also reacted to produce the desired product in 95% yield (entry 5). Furthermore, we effectively incorporated a highly electrophilic CF3-substituted tetrafluorophenyl group into the product, although a longer reaction time was required to complete the reaction and we obtained a slightly lower product yield (entry 6).

3. Experimental Section

1H and 13C NMR spectra were recorded at room temperature on 400 and 500 MHz spectrometers using perdeuterated solvents as internal standards. Chemical shifts of 1H and 13C spectra are given in ppm relative to residual protiated solvent and relative to the solvent respectively. 19F NMR spectra were recorded at rt on a 500 MHz spectrometer using benzotrifluoride as an external standard. The chemical shift values are expressed as δ values (ppm) and the couple constants values (J) are in Hertz (Hz). The following abbreviations were used for signal multiplicities: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; and br, broad. UV–visible spectra were recorded using a dual-beam grating spectro­photometer with a 1 cm quartz cell. The melting point data were not available for the porphyrin derivatives obtained because these compounds are infusible below 300 °C.

Reactions involving moisture sensitive reagents were carried out under an argon atmosphere using standard vacuum line techniques and glassware that was flame-dried and cooled under argon before use. Dry THF was purchased for the reactions and used without further desiccation. Bromoporphyrin derivatives, 1a1c [36], 1d [6], 1e1j [36], Zn-1a [36], and Ni-1a [36] were prepared according to the method described in literature. Other chemicals were purchased from commercial sources and used as received unless stated otherwise.

Preparation of Bis(polyfluorophenyl)zinc Reagents: Bis(polyfluorophenyl)zinc reagents, bis(2,3,5,6-tetrafluorophenyl)zinc, bis(3,4,5-trifluorophenyl)zinc, bis(2,6-difluorophenyl)zinc, bis(2,6-difluoro-4-methoxyphenyl)zinc, and bis(4-trifluoromethyl-2,3,5,6-tetrafluorophenyl)zinc, were prepared according to the method described in literature [37] as follows. An oven-dried 20 mL two-necked flask equipped with magnetic stirring bar and rubber septum charged with Zn(OMe)2 (118 mg, 0.925 mmol) was added dry THF (4.0 mL) at rt. The heterogeneous solution was stirred for 5 min and cooled to 0 °C for another 10 min. A solution of polyflurophenylmagnesium bromide (1.85 mL, 1.85 mmol, 1 M in THF) was added dropwise with vigorous stirring over 10 min at 0 °C, and the heterogeneous solution was allowed to stir at rt for 1 h. The mixture was then filtered and the Ar2Zn solution (ca. 0.15 M) was used immediately.

A solution of bis(pentafluorophenyl)zinc in THF (ca. 0.15 M) was prepared as follows. An oven-dried 20 mL two-necked flask equipped with magnetic stirring bar and rubber septum charged with bis(pentafluorophenyl)zinc (370 mg, 0.925 mmol) was added dry THF (6.0 mL) at room temperature The mixture was stirred for 10 min and used immediately.

General Procedure for the Palladium-Catalyzed Reaction of Bromoporphyrins with Bis(polyfluorophenyl)zinc Reagents: An oven-dried 100 mL two-necked flask equipped with a magnetic stirring bar and rubber septum was charged with a free base bromoporphyrin 1 (0.185 mmol), Pd(OAc)2 (2.1 mg, 9.3 μmol, 5 mol%), and t-Bu3P·HBF4 (5.4 mg, 18.5 μmol, 10 mol%). The reaction vessel was evacuated and flushed with argon (three times), and then dry THF (30 mL) was added. To the solution was slowly added ca. 0.15 M THF solution of a bis(polyfluorophenyl)zinc reagent (6.0 mL, ca. 0.9 mmol, 5 equiv.) at rt via a cannula. The mixture was stirred at 60 °C for several hours (1–12 h), having been monitored by TLC (1:1 hexane/toluene). Upon completion of the reaction, the mixture was allowed to reach rt. The reaction mixture was diluted with CH2Cl2 (50 mL) and washed with water and brine. The organic layer was dried over MgSO4 and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel (1:1 toluene/hexane). The first red purple band eluted was collected, and taken to dryness. Recrystallization from hexane/CH2Cl2 gave the pure product.

[5,15-Diphenyl-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2a). Prepared from bromoporphyrin 1a (100.2 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 121.9 mg, 95% yield; Rf = 0.60 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 10.32 (1H, s), 9.42 (2H, d, J = 4.4 Hz), 9.06 (4H, d, J = 4.4 Hz), 9.01 (2H, d, J = 4.4 Hz), 8.35–8.23 (4H, m), 7.87–7.74 (6H, m); 13C NMR (THF-d8, 100 MHz) δ 150.9, 150.3, 150.1, 149.3, 147.0 (2C, d, JCF = 246.6 Hz), 143.3, 141.9 (1C, d, JCF = 248.3 Hz), 137.8 (2C, d, JCF = 250.8 Hz), 134.7, 132.8, 132.1, 131.9, 129.3, 127.4, 126.4, 120.8, 118.5, 107.2, 100.6; 19F NMR (THF-d8, 466 MHz) δ −141.2 (2F, ddd, JFF = 24.6, 8.1, 5.9 Hz), –158.9 (1F, tt, JFF = 20.9, 5.9 Hz), −167.3 (2F, ddd, JFF = 24.6, 20.9, 8.0 Hz); IR (KBr) 3055, 3028, 2970, 2924, 2866, 2804, 1493, 1065, 991, 860, 764, 702 cm−1; UV/vis (CHCl3) λmax (log ε) 417.0 (5.7), 546.5 (4.3) nm; HRMS (EI) calcd. for C38H19F5N4Zn 690.0821, found 690.0822.

This compound was also synthesized from zinc complex of bromoporphyrin Zn-1a (111.9 mg, 0.185 mmol) and bis(pentafluorophenyl)zinc following the general procedure (see, Table 3, entry 9); 126.5 mg, 99% yield.

[5,15-Di(p-tolyl)-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2b). Prepared from bromoporphyrin 1b (105.4 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 124.1 mg, 93% yield; Rf = 0.61 (1:1 hexane/toluene); 1H NMR (CDCl3, 500 MHz) δ 9.76 (1H, s), 9.10 (2H, d, J = 4.6 Hz), 9.03 (2H, d, J = 4.6 Hz), 8.91 (4H, d, J = 4.6 Hz), 8.05 (4H, d, J = 7.6 Hz), 7.57 (4H, d, J = 7.6 Hz), 2.74 (6H, s); 13C NMR (CDCl3, 125 MHz) δ 150.6, 150.3, 149.2, 148.9, 146.6 (2C, d, JCF = 245.2 Hz), 141.7 (1C, d, JCF = 255.5 Hz), 139.3, 137.4 (2C, d, JCF = 252.4 Hz), 137.3, 134.5, 133.4, 132.5, 131.8, 129.5, 127.4, 121.2, 117.6, 106.9, 101.2, 21.5; 19F NMR (CDCl3, 466 MHz) δ −138.7 (2F, ddd, JFF = 24.5, 8.5, 6.4 Hz), −155.1 (1F, tt, JFF = 21.0, 6.4 Hz), −164.2 (2F, ddd, JFF = 24.5, 21.0, 8.4 Hz); IR (KBr) 3113, 3086, 3024, 2920, 2873, 2804, 1724, 1489, 1319, 1180, 1065, 995, 791 cm−1; UV/vis (CHCl3) λmax (log ε) 418.0 (5.6), 547.0 (4.2) nm; HRMS (EI) calcd. for C40H23F5N4Zn 718.1134, found 718.1138.

[5,15-Bis(3-vinylphenyl)-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2c). Prepared from bromoporphyrin 1c (109.8 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 121.4 mg, 88% yield; Rf = 0.57 (1:1 hexane/toluene); 1H NMR (CDCl3, 500 MHz) δ 10.22 (1H, s), 9.34 (2H, d, J = 4.6 Hz), 9.06 (2H, d, J = 4.6 Hz), 9.05 (2H, d, J = 4.6 Hz), 8.86 (2H, d, J = 4.6 Hz), 8.29 (2H, s), 8.13 (2H, d, J = 7.6 Hz), 7.84 (2H, d, J = 7.9 Hz), 7.71 (2H, dd, J = 7.9, 7.6 Hz), 7.00 (2H, dd, J = 17.7, 11.0 Hz), 5.98 (2H, d, J = 17.7 Hz), 5.40 (2H, d, J = 11.0 Hz); 13C NMR (CDCl3, 125 MHz) δ 150.6, 150.0, 149.7, 149.0, 146.6 (2C, d, JCF = 246.2 Hz), 143.1, 141.5 (1C, d, JCF = 254.5 Hz), 137.3 (2C, d, JCF = 251.4 Hz), 136.9, 135.7, 134.2, 133.1, 132.5, 132.4, 132.0, 129.4, 126.6, 125.2, 120.5, 118.0, 114.7, 107.2, 100.7; 19F NMR (CDCl3, 466 MHz) δ −138.7 (2F, ddd, JFF = 23.8, 7.2, 5.3 Hz), −154.9 (1F, tt, JFF = 21.0, 5.3 Hz), –164.1 (2F, ddd, JFF = 23.8, 21.0, 8.5 Hz); IR (KBr) 3089, 3020, 2981, 2924, 1489, 1319, 1173, 1065, 991, 910, 856, 791, 710 cm−1; UV/vis (CHCl3) λmax (log ε) 418.0 (5.7), 546.5 (4.3) nm; HRMS (EI) calcd. for C42H23F5N4Zn 742.1134, found 742.1131.

[5,15-Bis[4-{2-(triisopropylsilyl)ethynyl}phenyl]-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2d). Prepared from bromoporphyrin 1d (166.9 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid (recrystallized from MeOH/CH2Cl2); 189.1 mg, 97%; Rf = 0.68 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 9.67 (1H, s), 9.08 (2H, d, J = 4.9 Hz), 8.97 (2H, d, J = 4.9 Hz), 8.94 (2H, d, J = 4.9 Hz), 8.83 (2H, d, J = 4.9 Hz), 8.09 (4H, d, J = 8.3 Hz), 7.92 (4H, d, J = 8.3 Hz), 1.50-1.12 (42H, m); 13C NMR (CDCl3, 100 MHz) δ 150.3, 150.0, 149.4, 149.2, 146.8 (2C, d, JCF = 244.1 Hz), 142.4, 142.0 (1C, d, JCF = 252.4 Hz), 137.6 (2C, d, JCF = 254.9 Hz), 134.5, 133.3, 132.3, 132.1, 130.4, 129.9, 123.2, 120.4, 117.5, 107.3, 107.1, 101.9, 92.1, 18.9, 11.6; 19F NMR (CDCl3, 466 MHz) δ –138.6 (2F, ddd, JFF = 24.5, 7.6, 5.5 Hz), –154.7 (1F, tt, JFF = 20.9, 5.5 Hz), −163.9 (2F, dd, JFF = 24.5, 20.9, 8.0 Hz); IR (KBr) 3097, 3035, 2947, 2866, 1516, 1385, 1319, 1219, 1065, 995, 945, 818, 671 cm−1; UV/vis (CHCl3) λmax (log ε) 419.5 (5.7), 549.0 (4.4) nm; HRMS-FAB+ ([M + H]+) calcd for C60H60F5N4Si2Zn 1051.3568, found 1051.3578.

[5,15-Bis(2,4,6-trimethylphenyl)-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2e). Prepared from bromoporphyrin 1e (115.7 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 128.9 mg, 90% yield; Rf = 0.64 (1:1 hexane/toluene); 1H NMR (CDCl3, 500 MHz) δ 10.24 (1H, s), 9.36 (2H, d, J = 4.6 Hz), 8.92 (2H, d, J = 4.6 Hz), 8.91 (2H, d, J = 4.6 Hz), 8.83 (2H, d, J = 4.6 Hz), 7.31 (4H, s), 2.65 (6H, s), 1.82 (12H, s); 13C NMR (CDCl3, 125 MHz) δ 150.6, 150.1, 149.7, 149.0, 146.6 (2C, d, JCF = 246.2 Hz), 141.7 (1C, d, JCF = 251.4 Hz), 139.3, 138.5, 137.7, 137.4 (2C, d, JCF = 253.5 Hz), 132.7, 132.2, 131.5, 130.1, 127.8, 119.6, 117.4, 107.0, 100.7, 21.7, 21.5; 19F NMR (CDCl3, 466 MHz) δ –138.7 (2F, ddd, JFF = 24.3, 8.9, 6.7 Hz), –154.9 (1F, tt, JFF = 21.0, 6.7 Hz), –164.1 (2F, ddd, JFF = 24.3, 21.0, 8.5 Hz); IR (KBr) 3097, 2966, 2920, 2858, 1489, 1381, 1061, 995, 941, 852, 787 cm−1; UV/vis (CHCl3) λmax (log ε) 417.5 (5.7), 545.5 (4.3) nm; HRMS (EI) calcd for C44H31F5N4Zn 774.1760, found 774.1755.

[5,15-Bis(3-methoxyphenyl)-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2f). Prepared from bromoporphyrin 1f (111.3 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 124.2 mg, 89% yield; Rf = 0.45 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 10.25 (1H, s), 9.37 (2H, d, J = 4.6 Hz), 9.11 (4H, d, J = 4.6 Hz), 8.88 (2H, d, J = 4.6 Hz), 7.81 (2H, d, J = 7.5 Hz), 7.75 (2H, s), 7.65 (2H, dd, J = 8.4, 7.5 Hz), 7.32 (2H, d, J = 8.4 Hz), 3.95 (6H, s); 13C NMR (THF-d8, 100 MHz) δ 159.3, 151.6, 151.1, 151.0, 150.2, 147.8 (2C, d, JCF = 243.3 Hz), 145.4, 142.8 (1C, d, JCF = 254.9 Hz), 138.6 (2C, d, JCF = 249.9 Hz), 133.7, 133.0, 132.7, 130.2, 128.5, 128.0, 121.8, 121.5, 119.3, 114.0, 108.0, 101.5, 55.7; 19F NMR (THF-d8, 466 MHz) δ –138.5 (2F, ddd, JFF = 24.5, 8.4, 6.3 Hz), −155.1 (1F, tt, JFF = 21.0, 6.3 Hz), –164.3 (2F, ddd, JFF = 24.5, 21.0, 8.5 Hz); IR (KBr) 3097, 2931, 2862, 2839, 1593, 1489, 1281, 1161, 1061, 991, 783 cm−1; UV/vis (CHCl3) λmax (log ε) 417.5 (5.6), 546.0 (4.3) nm; HRMS (EI) calcd for C40H23F5N4O2Zn 750.1033, found 750.1031.

[5,15-Di(i-butyl)-10-pentafluorophenylporphyrinato]zinc(II) (Zn-2g). Prepared from bromopor­phyrin 1g (92.8 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 113.6 mg, 94% yield; Rf = 0.59 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 10.01 (1H, s), 9.53 (2H, d, J = 4.6 Hz), 9.52 (2H, d, J = 4.6 Hz), 9.30 (2H, d, J = 4.6 Hz), 8.77 (2H, d, J = 4.6 Hz), 4.86 (4H, d, J = 7.3 Hz), 2.80-2.69 (2H, m), 1.14 (12H, d, J = 6.7 Hz); 13C NMR (THF-d8, 100 MHz) δ 152.4, 151.8, 150.0, 149.3, 147.8 (2C, d, JCF = 241.7 Hz), 142.6 (1C, d, JCF = 251.6 Hz), 138.6 (2C, d, JCF = 252.4 Hz), 132.7, 131.2, 130.5, 130.1, 119.9, 119.8, 107.1, 100.1, 44.4, 38.1, 23.6; 19F NMR (THF-d8, 466 MHz) δ –138.8 (2F, ddd, JFF = 24.7, 8.9, 6.8 Hz), –156.0 (1F, tt, JFF = 20.6, 6.8 Hz), −164.9 (2F, ddd, JFF = 24.7, 20.6, 8.8 Hz); IR (KBr) 3113, 3028, 2958, 2870, 1493, 1381, 1315, 1165, 1076, 987, 949, 849, 775 cm−1; UV/vis (CHCl3) λmax (log ε) 417.0 (5.7), 549.0 (4.3) nm; HRMS (EI) calcd for C34H27F5N4Zn 650.1447, found 650.1451.

[5-Pentafluorophenyl-10,15,20-triphenylporphyrinato]zinc(II) (Zn-2h). Prepared from bromopor­phyrin 1h (114.2 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 136.1 mg, 96% yield; Rf = 0.62 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 8.98 (2H, d, J = 4.8 Hz), 8.91 (2H, d, J = 4.8 Hz), 8.89 (2H, d, J = 4.8 Hz), 8.81 (2H, d, J = 4.8 Hz), 8.27-8.17 (6H, m), 7.82-7.70 (9H, m); 13C NMR (THF-d8, 100 MHz) δ 151.7, 151.3, 151.1, 150.6, 147.9 (2C, d, JCF = 242.5 Hz), 144.4, 144.3, 142.8 (1C, d, JCF = 252.4 Hz), 138.7 (2C, d, JCF = 251.6 Hz), 135.4 (6C), 133.8, 132.8, 132.5, 130.3, 128.3 (3C), 127.3, 127.2, 123.5, 122.3, 119.3, 101.3; 19F NMR (THF-d8, 466 MHz) δ −139.1 (2F, ddd, JFF = 24.5, 8.4, 6.3 Hz), –155.8 (1F, tt, JFF = 20.9, 6.3 Hz), −164.8 (2F, ddd, JFF = 24.5, 20.9, 8.5 Hz); IR (KBr) 3055, 3024, 2962, 2920, 2858, 1489, 1338, 1068, 995, 941, 868, 756, 702 cm−1; UV/vis (CHCl3) λmax (log ε) 422.5 (5.7), 552.0 (4.3) nm; HRMS (EI) calcd. for C44H23F5N4Zn 766.1134, found 766.1133.

[2-Pentafluorophenyl-5,10,15,20-tetraphenylporphyrinato]zinc(II) (Zn-2i). Prepared from bromo­porphyrin 1i (128.3 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 144.0 mg, 92% yield; Rf = 0.63 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 8.94 (1H, s), 8.91 (2H, d, J = 4.9 Hz), 8.89 (2H, d, J = 4.9 Hz), 8.84 (1H, d, J = 4.9 Hz), 8.71 (1H, d, J = 4.9 Hz), 8.33-8.18 (6H, m), 8.13-8.04 (2H, m), 7.82-7.68 (9H, m), 7.57–7.42 (3H, m); 13C NMR (THF-d8, 100 MHz) δ 151.85 (4C), 151.8, 151.0, 148.3, 146.5, 144.7 (2C, d, JCF = 243.3 Hz), 144.4 (2C), 144.3, 143.1, 140.9 (1C, d, JCF = 249.1 Hz), 138.3 (2C, d, JCF = 242.5 Hz), 136.8, 135.5 (2C), 135.4 (4C), 135.0 (2C), 133.0, 132.8, 132.7 (2C), 132.6, 132.3, 128.6, 128.4, 128.3, 128.2 (2C), 127.3 (6C), 126.6 (2C), 122.1, 121.99, 121.96, 121.5, 116.7; 19F NMR (THF-d8, 466 MHz) δ –140.0 (2F, ddd, JFF = 24.3, 7.6, 5.5 Hz), −161.3 (1F, tt, JFF = 20.5, 5.5 Hz), −167.8 (2F, ddd, JFF = 24.3, 20.5, 7.5 Hz); IR (KBr) 3055, 3032, 2962, 2920, 2858, 2792, 2727, 1493, 1331, 1072, 995, 864, 795, 752 cm−1; UV/vis (CHCl3) λmax (log ε) 426.0 (5.7), 556.0 (4.3) 597.5 (3.8) nm; HRMS-FAB+ (M+) calcd for C50H27F5N4Zn 842.1447, found 842.1445.

[5,15-Bis(pentafluorophenyl)-10,20-diphenylporphyrinato]zinc(II) (Zn-2j). The general procedure with dibromoporphyrin 1i (114.8 mg) and 10 equiv, instead of 5 equiv, of bis(pentafluorophenyl)zinc (12 mL of its ca. 0.15 M solution in THF, ca. 1.8 mmol) gave the title compound as a red-purple solid (136.3 mg, 86% yield); Rf = 0.71 (1:1 hexane/toluene); Rf = 0.71 (1:1 hexane/toluene); 1H NMR (THF-d8, 400 MHz) δ 8.99 (4H, d, J = 4.9 Hz), 8.98 (4H, d, J = 4.9 Hz), 8.30–8.22 (4H, m), 7.85–7.73 (6H, m); 13C NMR (THF-d8, 100 MHz) δ 151.9, 150.5, 147.7 (4C, d, JCF = 241.7 Hz), 143.9, 142.9 (2C, d, JCF = 253.2 Hz), 138.7 (4C, d, JCF = 249.9 Hz), 135.4, 133.9, 130.8, 128.5, 127.3, 122.8, 118.9, 103.1; 19F NMR (THF-d8, 466 MHz) δ −138.7 (4F, ddd, JFF = 24.3, 8.0, 5.9 Hz), −154.5 (2F, tt, JFF = 21.0, 5.9 Hz), –163.9 (4F, ddd, JFF = 24.3, 21.0, 8.5 Hz); IR (KBr) 3105, 3059, 3020, 2927, 2854, 1493, 1338, 1076, 991, 941, 768, 706 cm−1; UV/vis (CHCl3) λmax (log ε) 421.5 (5.8), 551.5 (4.3) nm; HRMS-FAB+ (M+) calcd for C44H18F10N4Zn 856.0663, found 856.0662.

[5,15-Diphenyl-10-pentafluorophenylporphyrinato]nickel(II) (Ni-2a). Prepared from nickel complex of bromoporphyrin Ni-1a (110.7 mg) and bis(pentafluorophenyl)zinc following the general procedure; Red-purple solid; 126.8 mg, 97% yield; Rf = 0.65 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 9.55 (1H, s), 8.89 (2H, d, J = 4.9 Hz), 8.84 (2H, d, J = 4.9 Hz), 8.77 (2H, d, J = 4.9 Hz), 8.68 (2H, d, J = 4.9 Hz), 8.02-7.95 (4H, m), 7.74-7.61 (6H, m); 13C NMR (CDCl3, 100 MHz) δ 146.4 (2C, d, JCF = 247.5 Hz), 143.4, 143.2, 142.8, 141.96, 141.94 (1C, d, JCF = 253.2 Hz), 140.8, 137.6 (2C, d, JCF = 249.1 Hz), 133.8, 133.5, 132.6, 132.5, 129.9, 127.9, 126.9, 119.3, 116.0, 105.9, 100.8; 19F NMR (CDCl3, 466 MHz) δ –138.5 (2F, ddd, JFF = 24.1, 8.5, 6.4 Hz), −154.5 (1F, tt, JFF = 21.0, 6.4 Hz), −163.7 (2F, ddd, JFF = 24.1, 21.0, 8.0 Hz); IR (KBr) 3059, 3032, 1493, 1385, 1335, 1161, 1072, 995, 941, 856, 764, 702 cm−1; UV/vis (CHCl3) λmax (log ε) 406.0 (5.4), 521.5 (4.2) 553.5 (3.9) nm; HRMS (EI) calcd for C38H19F5N4Ni 684.0883, found 684.0880.

[5,15-Diphenyl-10-(2,3,5,6-tetrafluorophenyl)porphyrinato]zinc(II) (Zn-3). Prepared from bromo­porphyrin 1a (100.2 mg) and bis(2,3,5,6-tetrafluorophenyl)zinc following the general procedure; Red-purple solid; 119.4 mg, 96% yield; Rf = 0.60 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 10.14 (1H, s), 9.26 (2H, d, J = 4.8 Hz), 8.97 (2H, d, J = 4.8 Hz), 8.96 (2H, d, J = 4.8 Hz), 8.82 (2H, d, J = 4.8 Hz), 8.21-8.15 (4H, m), 7.73-7.65 (6H, m), 7.51 (1H, tt, JHF = 10.0, 7.1 Hz); 13C NMR (CDCl3, 100 MHz) δ 150.5, 150.0, 149.6, 148.8, 146.3 (2C, d, JCF = 245.8 Hz), 145.6 (2C, d, JCF = 249.1 Hz), 142.9, 134.5, 132.8, 132.2, 131.7, 129.3, 127.2, 126.3, 123.9, 120.6, 106.9, 106.1, 102.0; 19F NMR (CDCl3, 466 MHz) δ –139.8 (2F, ddd, JFF = 22.5, 7.8 Hz, JFH = 5.6 Hz), −141.7 (2F, ddd, JFF = 22.5, 7.5 Hz, JFH = 8.8 Hz); IR (KBr) 3059, 2974, 2877, 2746, 1593, 1493, 1385, 1315, 1173, 1065, 999, 941, 852, 783, 710 cm−1; UV/vis (CHCl3) λmax (log ε) 417.0 (5.7), 546.0 (4.3) nm; HRMS-FAB+ (M+) calcd for C38H20F4N4Zn 672.0916, found 672.0918.

[5,15-Diphenyl-10-(3,4,5-trifluorophenyl)porphyrinato]zinc(II) (Zn-4). Prepared from bromoporphyrin 1a (100.2 mg) and bis(3,4,5-trifluorophenyl)zinc following the general procedure; Red-purple solid; 119.2 mg, 98% yield; Rf = 0.58 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 10.17 (1H, s), 9.32 (2H, d, J = 4.8 Hz), 9.02 (2H, d, J = 4.8 Hz), 8.95 (2H, d, J = 4.8 Hz), 8.85 (2H, d, J = 4.8 Hz), 8.25-8.16 (4H, m), 7.83 (2H, dd, JHF = 8.3, 6.8 Hz), 7.79-7.70 (6H, m); 13C NMR (CDCl3, 100 MHz) δ 150.3, 150.0, 149.8, 149.2 (2C, d, JCF = 250.8 Hz), 148.7, 143.0, 139.7 (1C, d, JCF = 252.4 Hz), 139.6, 134.5, 132.2, 132.0, 131.6, 130.4, 127.2, 126.3, 120.4, 118.5, 116.5, 105.9; 19F NMR (CDCl3, 466 MHz) δ –138.7 (2F, ddd, JFF = 20.5, 8.0 Hz, JFH = 8.6 Hz), –164.4 (1F, tt, JFF = 20.5 Hz, JFH = 5.7 Hz); IR (KBr) 3062, 2958, 2927, 2862, 2804, 1608, 1527, 1435, 1377, 1234, 1045, 999, 791, 725 cm−1; UV/vis (CHCl3) λmax (log ε) 417.5 (5.7), 546.0 (4.3) nm; HRMS (EI) calcd for C38H21F3N4Zn 654.1010, found 654.1010.

[10-(2,6-Difluorophenyl)-5,15-diphenylporphyrinato]zinc(II) (Zn-5). Prepared from bromoporphyrin 1a (100.2 mg) and bis(2,6-difluorophenyl)zinc following the general procedure; Red-purple solid; 109.5 mg, 93% yield; Rf = 0.51 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 10.13 (1H, s), 9.27 (2H, d, J = 4.4 Hz), 8.98 (2H, d, J = 4.4 Hz), 8.93 (2H, d, J = 4.4 Hz), 8.85 (2H, d, J = 4.4 Hz), 8.24–8.15 (4H, m), 7.75–7.61 (7H, m), 7.28 (2H, dd, JHF = 8.3 Hz, JHH = 6.8 Hz); 13C NMR (CDCl3, 100 MHz) δ 162.6 (2C, dd, JCF = 247.0, 6.2 Hz), 150.3, 150.0, 149.5, 149.4, 143.1, 134.5, 132.3, 132.0, 131.5, 130.1 (1C, t, JCF = 9.9 Hz), 130.0, 127.1, 126.2, 120.5 (1C, t, JCF = 21.5 Hz), 120.2, 110.8 (2C, dd, JCF = 19.0, 6.6 Hz), 106.3, 105.0; 19F NMR (CDCl3, 466 MHz) δ −110.5 (2F, ddd, JFF = 7.8 Hz, JFH = 8.5, 5.6 Hz); IR (KBr) 3062, 3024, 2970, 2877, 2742, 1589, 1462, 1315, 1065, 995, 849, 787, 710 cm−1; UV/vis (CHCl3) λmax (log ε) 416.5 (5.6), 545.5 (4.2) nm; HRMS (EI) calcd. for C38H22F2N4Zn 636.1104, found 636.1097.

[10-(2,6-Difluoro-4-methoxyphenyl)-5,15-diphenylporphyrinato]zinc(II) (Zn-6). Prepared from bromoporphyrin 1a (100.2 mg) and bis(2,6-difluoro-4-methoxyphenyl)zinc following the general procedure; Red-purple solid; 117.6 mg, 95% yield; Rf = 0.47 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 10.06 (1H, s), 9.23 (2H, d, J = 4.4 Hz), 8.95 (2H, d, J = 4.4 Hz), 8.89 (2H, d, J = 4.4 Hz), 8.86 (2H, d, J = 4.4 Hz), 8.21-8.12 (4H, m), 7.71 (2H, d, JHF = 8.3 Hz), 7.70–7.62 (6H, m), 4.23 (3H, s); 13C NMR (CDCl3, 100 MHz) δ 153.6 (2C, dd, JCF = 249.1, 6.6 Hz), 150.2, 150.0, 149.8, 149.0, 143.1, 138.5 (1C, t, JCF = 9.1 Hz), 136.0 (1C, t, JCF = 14.1 Hz), 134.5, 132.2, 131.8, 131.5, 130.7, 127.1, 126.2, 120.2, 118.5 (2C, dd, JCF = 16.1, 7.0 Hz), 117.4, 105.7, 61.8; 19F NMR (CDCl3, 466 MHz) δ −133.0 (2F, dd, JFF = 8.0 Hz, JFH = 5.5 Hz); IR (KBr) 3059, 3020, 2951, 2862, 1574, 1516, 1435, 1346, 1246, 999, 860, 791, 748, 702 cm−1; UV/vis (CHCl3) λmax (log ε) 417.5 (5.6), 547.0 (4.2) nm; HRMS (EI) calcd for C39H24F2N4OZn 666.1210, found 666.1210.

[5,15-Diphenyl-10-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)porphyrinato]zinc(II) (Zn-7). Prepared from bromoporphyrin 1a (100.2 mg) and bis(4-trifluoromethyl-2,3,5,6-tetrafluorophenyl)zinc following the general procedure; Red-purple solid; 96.5 mg, 70% yield; Rf = 0.65 (1:1 hexane/toluene); 1H NMR (CDCl3, 400 MHz) δ 10.13 (1H, s), 9.24 (2H, d, J = 4.6 Hz), 8.95 (2H, d, J = 4.6 Hz), 8.95 (2H, d, J = 4.6 Hz), 8.77 (2H, d, J = 4.6 Hz), 8.20-8.10 (4H, m), 7.74–7.61 (6H, m); 13C NMR (CDCl3, 100 MHz) δ 150.7, 150.0, 149.7, 148.1, 146.6 (2C, d, JCF = 248.3 Hz), 143.8 (2C, d, JCF = 260.7 Hz), 142.7, 134.6 (1C, q, JCF = 29.8 Hz), 134.5, 133.1, 132.3, 131.8, 128.8, 127.3, 126.3, 121.2 (1C, q, JCF = 274.8 Hz), 120.8, 109.8, 107.3, 99.9; 19F NMR (CDCl3, 466 MHz) δ −57.6 (3F, t, JFF = 22.3 Hz), −137.2 (2F, dd, JFF = 21.4, 7.6 Hz), −143.4 (2F, qdd, JFF = 22.3, 21.4, 8.7 Hz); IR (KBr) 3059, 1643, 1462, 1319, 1146, 991, 957, 748, 702 cm−1; UV/vis (CHCl3) λmax (log ε) 418.0 (5.7), 547.5 (4.3) nm; HRMS (EI) calcd for C39H19F7N4Zn 740.0789, found 740.0794.

4. Conclusions

In summary, we have developed an efficient and facile palladium-catalyzed polyfluorophenylation of porphyrins. The success of this reaction relies on the use of readily accessible bis(polyfluorophenyl)zinc reagents as the polyfluorophenylation agent; furthermore, t-Bu3P was the only effective ligand. The method is compatible with a wide array of free-base meso-mono-, meso-di-, and β-bromo-substituted porphyrins, their metal complexes, and a variety of bis(polyfluorophenyl)zinc reagents. The reaction generally achieves good to excellent yields. We anticipate that this method will find broad application among practitioners of porphyrin chemistry.

Acknowledgments

This work was partially supported by a Grant-in-Aid for Scientific Research (KAKENHI) from JSPS and a grant from the High-Tech Research Center Project, MEXT, Japan.

Conflicts of Interest

The authors declare no conflict of interest.

References and Notes

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