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Article

Reactivity of a-Oxophosphonium Ylides: A Contribution to the Mechanistics

Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3000 Coimbra, Portugal
*
Author to whom correspondence should be addressed.
Molecules 1999, 4(7), 219-231; https://doi.org/10.3390/40700219
Submission received: 9 June 1999 / Accepted: 29 June 1999 / Published: 17 July 1999

Abstract

:
Ylides 1f and 1g react with chlorine, with bromine and with N-chlorosuccinimide in the presence of a range of nucleophiles. The 2,3-disubstitutedbutenedioates obtained in this way allow us to gather more information about the mechanism involved. Ylide 1c was also studied showing similar reactivity and leading to the highly selective synthesis of 2,3-disubstituted-3-phenylpropenoates.

Introduction

We have previously studied the reactivity of diethyl 2-oxo-3-triphenylphosphoranylidene-butanedioate 1a with chlorine and bromine in the presence of a range of nucleophiles [1]. Triphenylphosphine oxide was eliminated and 2,3-disubstituted diethyl butenedioates were formed (Scheme 1). The reaction of N-bromosuccinimide and N-chlorosuccinimide in methanol also gave 2,3- isubstituted diethylbutenedioates. Several of the reactions were highly stereoselective whereas others gave both (E) and (Z) isomers. The method offers a route to some simple tetrasubstituted alkenes of a type that was poorly represented in the literature.
The formation of the observed products was explained by postulating isomeric halonium ions as intermediates. These halonium ions could interconvert by way of an acyclic cation (Scheme 2). The opening of the two halonium ions by a nucleophile would lead to the isomeric alkenes after the elimination of triphenylphosphine oxide.
α-Oxophosphonium ylides (1a1e) also react with N-chlorosuccinimide and N-bromosuccinimide in the presence of azidotrimethylsilane giving the corresponding haloazidoalkenes (2) with elimination of triphenylphosphine oxide [1,2]. These compounds were completely converted into the corresponding 2H-azirines 3 on heating in heptane (Scheme 3) [2].
Abell et al [3] has also described the reaction of α-oxophosphonium ylides, bearing a terminal carboxylic acid group acting as the nucleophile, with Br2 or SOCl2 and NEt3 which leads to the formation of E- and Z-halo enol lactones. The cyclization proceeds via a halophosphonium salt followed by loss of triphenylphosphine oxide.

Results and Discussion

We decided to investigate this type of reactions with ylides with the general structure 1 where R1 and R2 are ester groups, the ylides 1f and 1g. These compounds should show a reactivity similar to 1a in the reaction with halogens and N-chlorosuccinimide in the presence of nucleophiles. However, since ylides 1f and 1g have R1 ≠ R2 the study of these reactions with a reagent system XY (electrophile/nucleophile), where X ≠ Y, could allow the gathering of more information concerning the proposed mechanism.
The stabilized ylides 3-oxo-2-triphenylphosphoranylidinebutanedioates 1f and 1g were prepared and their reactions studied. The comparision of the product obtained from 1a [1] with those from 1f and 1g allowed us to establish their stereochemistry.
Ylide 1f reacted with chlorine giving, after 5 minutes, the ethyl methyl (Z)-2,3-dichlorobutenedioate (Z)-4 in 72% yield (Table 1). The reaction of 1f with hypobromous acid and acetic acid was a stereoselective process giving, after 24 hours, the isomer (Z)-5 in 78% yield. On the other hand, the reaction with hipochlorous acid and acetic acid gave a mixture of isomers (Z)-6 and (E)-6 (49:51) in 49% overall yield. Ylide 1f also reacted with chlorine in methanol giving the alkene (E)-7 in 44% yield.
Table 2 shows the results obtained with ylide 1g. The reaction with hypobromous acid and acetic acid gave this time a mixture of isomers (Z)-8 and (E)-8 being the Z isomer the major component (78:22) in 88% overall yield. The reaction with hypochlorous acid and acetic acid gave a mixture of isomers (Z)-9 and (E)-9 in 50% yield. Ylide 1g also reacted with N-chlorosuccinimide in the presence of methanol giving alkene (E)-10 in 44% yield.
On the basis of the 13C nmr analysis it was possible to determine the regioisomers obtained in the reactions of ylides 1f and 1g. From the 13C nmr of diethyl (Z)-2,3-dichlorobutenedioate and of ethyl methyl (Z)-2,3-dichlorobutenedioate (Z)-4 we could determine the effect of the substitution of an ethyl ester group by a methyl ester group (Table 3). This substitution leads to a decrease of the chemical shift of the α carbon (Δδ = - 0.43) and an increase of the chemical shift of the β carbon (Δδ = + 0.31).
The values for the chemical shifts of double bond carbons of alkenes 4-10 were estimated by adding these increments to the chemical shifts of the corresponding diethyl esters. Table 4 shows the results of this analysis for the products (the Z isomers) of the reactions of ylides 1f and 1g with hypobromous and hypochlorous acids in the presence of acetic acid. The comparison of the estimated values with the experimental values allow us to define the regioisomers obtained in each case. The same analysis was carried out with the other alkenes.
These results show that the electrophile attacks the carbon of the triphenylphosphoranylidene group of the starting ylide as postulated in Scheme 2. This fact is in agreement with the known halogenation of α-oxophosphonium ylides which gives the salt 11 [4] (Scheme 4).
The reactivity of ylide 1c was also studied. We have previously described the reaction of this ylide with NCS or NBS in the presence of azidotrimethylsilane leading to the corresponding haloazidoalkene with high selectivity [2] (Scheme 3) The reaction of the same ylide with chlorine led to the formation of dichloroalkene 12 with elimination of triphenylphosphine oxide. By analogy with the reactivity of the previously studied ylides we concluded that 12 was the Z isomer and was obtained in 69% yield (Table 5). The reaction with hipobromous acid and acetic acid gave 13 (60% yield) and the reaction with N-chlorosuccinimide in methanol gave alkene 14 in 98% yield. In all cases the reactions showed high stereoselectivity.

Conclusion

The results obtained from the study of the reactivity of ylides 1f, 1g and 1c clearly indicate that the reactions studied follow the mechanism described in Scheme 2, where the halogen binds exclusively to the carbon of the phosphoranylidene group of the starting ylide and the oxygen which is eliminated in the process is from the keto carbonyl group.
This work allowed the synthesis of a range of tetrasubstituted alkenes, 2,3-disubstituted-butenedioates (4-10) and 2,3-disubstituted-3-phenylpropenoates (12-14).

Experimental

General

Unless otherwise indicated all common reagents and solvents were used as obtained from commercial suppliers without further purification. IR spectra were recorded on a Perkin Elmer 1720X FTIR spectrometer. 1H and 13C NMR spectra were recorded in deuteriochloroform on a Bruker AMX300 spectrometer. Mass spectra were recorded on a VG Micromass 7070E instrument by chemical ionisation (CI) with isobutane (except where indicated otherwise) or where indicated under electron impact. M.p.’s were recorded on a Leitz Wetzlar 799 hot stage and are uncorrected. Flash column chromatography was performed with Merck 9385 silica as the stationary phase.

1-Ethyl 4-methyl 2-oxo-3-triphenylphosphoranylidenebutanedioate (1f)

Methyl triphenylphosphoranylideneacetate [6] (10.93 g, 32.7 mmol) was dissolved in toluene (80 mL) and the resulting solution was cooled at 5–10 °C. Ethyl oxalyl chloride (3.6 mL, 32.83 mmol) was added dropwise. The reaction mixture was stirred at 5–10 °C for 5 min then at room temperature for 30 min. Diethyl ether (80 mL) was added and an oil separated out. The solution was decanted from the oil and the solvent was removed under reduced pressure. The residue was triturated with ether to give a colourless solid which was isolated by filtration. Water was added to the oil separated by decantation and the resulting solution was extracted with chloroform. After evaporating the solvent and addition of ether, more solid was obtained, giving altogether 8.66 g (70%).
Mp 170 - 172 °C (lit. [7], 173 - 174°C).
1H NMR δ: 1.37 (t, 3H, CH3CH2), 3.32 (s, 3H, CH3), 4.33 (q, 2H, CH3CH2), 7.27 - 7.73 (m, 15H, Ar-H).
13C NMR δ: 14.05, 50.13, 60.84, 122.95, 124.80, 128.52, 128.77, 132.41, 132.36, 133.39, 133.59, 154.39, 154.51, 167.22, 167.41, 184.59, 184.51.
IR (KBr) cm−1 2920, 1730, 1665.

4-Ethyl 1-methyl 2-oxo-3-triphenylphosphoranylidenebutanedioate (1g)

Ethyl triphenylphosphoranylideneacetate [6] (10.39 g, 29.84 mmol) was dissolved in toluene (75 mL) and the resulting solution was cooled at 5–10 °C. Methyl oxalyl chloride (2.1 mL, 29.96 mmol) was added dropwise. The reaction mixture was stirred at 5–10 °C for 5 min then at room temperature for 30 min. Diethyl ether (70 mL) was added and an oil separated out. The solution was decanted from the oil and the solvent was removed under reduced pressure. The residue was triturated with ether to give a colourless solid which was isolated by filtration. Water was added to the oil separated by decantation and the resulting solution was extracted with chloroform. After evaporating the solvent and addition of ether, more solid was obtained, giving altogether 7.46 g (62%).
Mp 110 °C (lit. [7], 115 - 118°C).
1H NMR δ: 0.76 (t, 3H, CH3CH2), 3.82 (q, 2H, CH3CH2), 3.85 (s, 3H, OCH3), 7.47 - 7.86 (m, 15H, Ar-H).
IR (KBr) cm−1 2980, 1724, 1674.

Ethyl 3-oxo-3-phenyl-2-triphenylphosphoranylidenepropanoate [5] (1c)

Ethyl triphenylphosphoranylideneacetate [6] (5 g, 14.4 mmol) was dissolved in dry THF (50 mL) and NEt3 was added (2 ml, 19.4 mmol). Benzoyl chloride (2 g, 16 mmol) was added dropwise. The reaction mixture was stirred under nitrogen at room temperature for 19 hours. The solution was filtered and the solid was washed with THF. The solvent was removed under reduced pressure and the residue was dissolved in chlroform. The organic phase was washed with water and dried over MgSO4. The residue obtained upon removal of the solvent was purified by crystallization [ethyl acetate–hexane (2:1)] leading to 1c, as a white solid (4.5 g, 72%).
Mp 94.3 - 97 °C.
1H NMR δ: 0.58 (t, 3H, CH3CH2), 3.67 (q, 2H, CH3CH2), 7.30 - 7.36 (m, 3H, Ar-H), 7.43 - 7.56 (m, 9H, Ar-H), 7.67 - 7.70 (m, 2H, Ar-H),7.73 - 7.81 (m, 6H, Ar-H).
IR (KBr) cm−1 3051, 1671, 1530.
MS (EI) m/z (%) 452 (100), 423 (23), 379 (64), 347 (30), 77 (65).
Anal. Calc. for C29H25PO3: C, 76.96; H, 5.57. Found: C, 76.34; H, 5.46.

Ethyl methyl (Z)-2,3-dichlorobutenedioate (Z)-4

The ylide 1f (5.82 g, 13.35 mmol) was dissolved in chloroform (120 mL) and a solutions of chlorine (1 g, 14.1 mmol) in chloroform (120 mL) was added The mixture was stirred at room temperature for 5 min. The organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and isolation of the diester (Z)-4, an oil, that was purified by distillation at 73 °C/0.1.7 Torr (2.18 g, 72%).
1H NMR δ: 1.35 (t, 3H, CH3CH2), 3.88 (t, 3H, CH3) and 4.34 (q, 2H, CH3CH2)..
13C NMR δ: 13.81 (q), 53.45 (q), 63.25 (t), 130.06 (s), 130.81 (s), 161.12 (s),161.72 (s).
IR (film) cm−1 1745, 1600
MS (CI) m/z (%) 227 [M(35Cl) + H+] (17), 191 (25), 181 (55), 167 (12).

1-Ethyl 4-methyl (Z)-2-acetoxy-3-bromobutenedioate (Z)-5

The ylide 1f (3.87 g, 8.9 mmol) was dissolved in a mixture of acetic acid (35 mL) and chloroform (75 mL) and solutions of bromine (1.17 g, 7.3 mmol) and sodium bicarbonate (0.87 g, 10.3 mmol) in water (75 mL) were added. The reaction mixture was stirred at room temperature for 24 h and the organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and isolation of the diester (Z)-5, an oil, that was purified by distillation at 112.5 °C/0.1.7 Torr (2.04 g, 78%).
1H NMR δ: 1.32 (t, 3H, CH3CH2), 2.25 (s, 3H, CH3CO), 2.32 (s, 3H, CO2CH3), 4.29 (q, 2H, CH3CH2).
13C NMR δ: 13.71, 20.11, 53.51, 62.64, 115.12 (3-C), 141.25 (2-C), 159.07, 163.10, 165.17
IR (film) cm−1 2986, 1762, 1736
MS (CI) m/z (%) 295 [M(79Br) + H+] (82), 279 (12), 265 (22), 221 (29).

1-Ethyl 4-methyl (Z)- and (E)-2-acetoxy-3-chlorobutenedioate (Z)-6 / (E)-6

The ylide 1f (5.82 g, 13.35 mmol) was dissolved in a mixture of acetic acid (52.5 mL) and chloroform (110 mL) and a solution of chlorine (7.8 g, 10.95 mmol) and sodium bicarbonate (1.32 g, 15.45 mmol) in water (110 mL) was added. The reaction mixture was stirred at room temperature for 24 h and the organic phase was then washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and the isolation of a mixture of the alkenes (Z)-6 and (E)-6 (49:51) (1.76 g, 49%) as an oil
1H NMR (Z)-6 δ: 1.26 (t, 3H, CH3CH2), 2.24 (s, 3H, COCH3), 3.87 (s, 3H, CO2CH3), 4.27 (q, 2H, CH3CH2).
13C NMR (Z)-6 δ: 13.62, 19.94, 53.40, 62.52, 124.54 (3-C), 139.82 (2-C), 159.48, 161.41, 166.88
1H NMR (E)-6 δ: 1.34 (t, 3H, CH3CH2), 2.30 (s, 3H, COCH3), 3.89 (s, 3H, CO2CH3), 4.34 (q, 2H, CH3CH2).
13C NMR (E)-6 δ 13.75, 19.94, 53.40, 62.41, 122.28 (3-C), 141.32 (2-C), 159.94, 162.23, 167.72.
IR (film) cm−1 2995, 2980, 1785, 1740, 1640.
MS (CI) m/z (%) 251 [M(35Cl) + H+] (84), 221 (12), 177 (10).

4-Ethyl 1-methyl 2-chloro-3-methoxybutenedioate (E)-7

The ylide 1f (5.82 g, 13.35 mmol) was dissolved in chloroform (60 mL) and a solution of chlorine (2.55 g, 36 mmol) in methanol (45 mL) was added. The reaction was complete after 5 min at room temperature. The organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and the isolation of the enol ether (E)-7 (1.33 g, 44%) as an oil.
1H NMR δ: 1.39 (t, 3H, CH3CH2), 3.80 (s, 3H, CH3O), 3.89 (s, 3H, CO2CH3), 4.40 (q, 2H, CH3CH2).
13C NMR δ: 13.83, 52.80, 58.20, 62.74, 105.20 (2-C), 156.01 (3-C), 161.73, 163.22.
IR (film) cm−1 2955, 1742, 1612.
MS (CI) m/z (%) 223 [M(35Cl) + H+] (88), 177 (100), 163 (31), 149 (70).

4-Ethyl 1-methyl (Z)-2-acetoxy-3-bromobutenedioate (Z)-8 / (E)-8

The ylide 1c (3.87 g, 8.9 mmol) was dissolved in a mixture of acetic acid (35 mL) and chloroform (75 mL) and solutions of bromine (1.17 g, 7.3 mmol) and sodium bicarbonate (0.87 g, 10.3 mmol) in water (75 mL) were added. The reaction mixture was stirred at room temperature for 24 h and the organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and isolation of the mixture (Z)-8 / (E)-8 (78:22), an oil, that was purified by distillation at 112 °C/1.7 Torr (2.31 g, 88%).
1H NMR (Z)-8 δ: 1.36 (t, 3 H, CH3CH2), 2.31 (s, 3 H, CH3CO), 3.81 (s, 3 H, CO2CH3), 4.35 (q, 2 H, CH3CH2).
13C NMR (Z)-8 δ: 13.79, 20.17, 53.11, 63.04, 116.97 (3-C), 140.84 (2-C), 159.77, 162.59 and 167.68.
1H NMR (E)-8 δ: 1.34 (t, 3 H, CH3CH2), 2.23 (s, 3 H, CH3CO), 2.86 (s, 3 H, CO2CH3), 4.32 (q, 2 H, CH3CH2).
13C NMR (E)-8 δ:13.94, 20.06, 52.99, 62.95, 111.37 (3-C), 140.83 (2-C), 160.83, 161.79 and 167.33.
IR (film) cm−1 3000, 1782, 1738, 1638
MS (CI-CH4) m/z (%) 296 [M(81Br)] (100), 262 (8) and 252 (55).
Anal. Calc. for C9H11BrO6: C, 36.63; H, 3,76. Found: C, 36.69; H, 3.73.

4-Ethyl 1-methyl (Z)- and (E)-2-acetoxy-3-chlorobutenedioate (Z)-9 / (E)-9

The ylide 1g (5.82 g, 13.35 mmol) was dissolved in a mixture of acetic acid (52.5 mL) and chloroform (110 mL) and a solution of chlorine (7.8 g, 10.95 mmol) and sodium bicarbonate (1.32 g, 15.45 mmol) in water (110 mL) was added. The reaction mixture was stirred at room temperature for 24 h and the organic phase was then washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and the isolation of a mixture of the alkenes (Z)-9 and (E)-9 (1.67 g, 50%) as an oil, that was purified by distillation at 133 °C/1.7 Torr.
1H NMR (Z)-9 δ: 1.24 (t, 3H, CH3CH2), 2.26 (s, 3H, COCH3), 3.74 (s, 3H, CO2CH3), 4.13 (q, 2H, CH3CH2).
13C NMR (Z)-9 δ: 13.92, 20.08, 53.08, 62.96, 125.23 (3-C), 139.82 (2-C), 160.24, 161.05, 167.41.
1H NMR (E)-9 δ: 1.31 (t, 3H, CH3CH2), 2.20 (s, 3H, COCH3), 3.77 (s, 3H, CO2CH3), 4.34 (q, 2H, CH3CH2).
13C NMR (E)-9 δ:14.00, 20.08, 53.02, 62.81, 123.28 (3-C), 140.71 (2-C), 160.63, 161.79 and 167.04.
IR (film) cm−1 2988, 1741, 1636.
MS (EI) m/z (%) 250 [M(35Cl)]+ (53), 218 (8) and 156 (26).

4-Ethyl 1-methyl 3-chloro-2-methoxybutenedioate (E)-10

The ylide 1g (3.84 g, 8.8 mmol) was dissolved in chloroform (40 mL) and a solution of N-chlorosuccinimide (1.2 g, 8.8 mmol) in methanol (64 mL) was added. The reaction was complete after 5 min at room temperature. The organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (2:1)] leading to the separation of triphenylphosphine oxide and the isolation of the enol ether (E)-10 (1.33 g, 44%) as an oil, that was purified by distillation at 119 °C/1.7 Torr.
1H NMR δ: 1.33 (t, 3H, CH3CH2), 3.87 (s, 3H, OCH3), 3.92 (s, 3H, OCH3), 4.24 (q, 2H, CH3CH2).
13C NMR δ: 13.68, 52.83, 58.01, 61.81, 105.54 (3-C), 155.30 (2-C), 161.98, 162.34.
IR (film) cm−1 2957, 1744, 1613.
MS (EI) m/z (%) 222 [M(35Cl)]+ (30), 207 (10), 163 (28) and 59 (100).

Ethyl (Z)-2,3-dichloro-3-phenylpropenoate (12)

The ylide 1c (4.0 g, 8.82 mmol) was dissolved in chloroform (82 mL) and a solutions of chlorine (3.3 g, 47 mmol) in chloroform (80 mL) was added The mixture was stirred at room temperature for 1 h. The organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (1:1)] leading to the separation of triphenylphosphine oxide and isolation of 12, an oil, that was purified by distillation at 23 °C / 2.5 Torr (1.5 g, 69%).
1H NMR δ: 1.17 (t, 3H, CH3CH2), 4.31 (q, 2H, CH3CH2), 7.45 - 7.50 (m, 2H, Ar-H), 7.59 - 7.64 (m, 1H, Ar-H), 8.02 - 8.05 (m, 2H, Ar-H).
13C NMR δ: 13.49, 64.68, 82.01 (2-C), 128.74, 129.97, 130.85, 134.30, 163.90 (3-C), 183.09.
IR (film) cm−1 1765, 1689, 1250.

Ethyl (Z)-3-acetoxy-2-bromo-3-phenylpropenoate (13)

The ylide 1c (2.0 g, 4.45 mmol) was dissolved in a mixture of acetic acid (17.5 mL) and chloroform (37.5 mL) and solutions of bromine (0.23 ml, 4.45 mmol) and sodium bicarbonate (0.528 g, 6.59 mmol) in water (45.5 mL) were added. The reaction mixture was stirred at room temperature for 20 h and the organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (1:1)] leading to the separation of triphenylphosphine oxide and isolation of 13, an oil, that was purified by distillation at 82.5°C/1.5 Torr (0.84 g, 60%).
1H NMR δ: 1.14 (t, 3 H, CH3CH2), 2.25 (s, 3 H, AcO), 4.29 (q, 2 H, CH3CH2), 7.42 - 7.48 (m, 2 H, Ar-H), 7.57 - 7.62 (m, 1 H, Ar-H), 8.04 - 8.06 (m, 2 H, Ar-H).
13C NMR δ: 13.49, 20.79, 64.68, 105.87 (2-C), 128.21, 128.58, 130.07 (3-C), 130.59, 133.94, 155.42 and 182.95..
IR (film) cm−1 2985, 1728, 1707, 1694.
MS (CI-CH4) m/z (%) 313 [M(79Br) + H+] (28), 253 (42) and 233 (100).

Ethyl (E)-2-chloro-3-methoxy-3-phenylpropenoate (14)

The ylide 1c (0.5 g, 1.1 mmol) was dissolved in chloroform (5 mL) and a solution of N-chlorosuccinimide (0.15 g, 1.1 mmol) in methanol (8 mL) was added. The reaction was complete after 10 min at room temperature. The organic phase was washed with an aqueous solution of sodium bisulfite and dried over MgSO4. The residue obtained upon removal of the solvent was purified by column chromatography [ethyl acetate–hexane (3:1)] leading to the separation of triphenylphosphine oxide and the isolation of 14 (0.26 g, 98%) as an oil, that was purified by distillation at 91.7 °C/1.5 Torr.
1H NMR δ: 1.37 (t, 3H, CH3CH2), 3.51 (s, 3H, OMe), 4.39 (q, 2H, CH3CH2), 7.44 - 7.49 (m, 2H, Ar-H), 7.59 - 7.62 (m, 1H, Ar-H), 8.02 - 8.05 (m, 2H, Ar-H).
13C NMR δ: 13.48, 58.95, 64.61, 81.85 (2-C), 128.59, 129.99, 130.78, 134.16, 163.96 (3-C), 183.12.
IR (film) cm−1 2986, 1767, 1715, 1646.
MS (EI) m/z (%) 240 [M(35Cl)]+ (3), 195 (3), 153 (2), 77 (45).

References and Notes

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  • Samples Availability: Samples available from the authors.
Scheme 1.
Scheme 1.
Molecules 04 00219 sch001
Scheme 2.
Scheme 2.
Molecules 04 00219 sch002
Scheme 3.
Scheme 3.
Molecules 04 00219 sch003
Figure 1.
Figure 1.
Molecules 04 00219 g001
Figure 2.
Figure 2.
Molecules 04 00219 g002
Figure 3.
Figure 3.
Molecules 04 00219 g003
Scheme 4.
Scheme 4.
Molecules 04 00219 sch004
Figure 4.
Figure 4.
Molecules 04 00219 g004
Table 1. Products obtained from the ylide 1f.
Table 1. Products obtained from the ylide 1f.
ReagentsXYProductsYield (%)
Cl2ClCl(Z)-472
HOBr/AcOHBrOAc(Z)-578
HOCl/AcOHClOA(Z)-6, (E)-6 (49:51)49
Cl2/MeOHClOMe(E)-744
Table 2. Products obtained from the ylide 1g.
Table 2. Products obtained from the ylide 1g.
ReagentsXYProductsYield (%)
HOBr/AcOHBrOAc(Z)-8, (E)-8 (78:22)88
HOCl/AcOHClOAc(Z)-9, (E)-9 (47:53)50
NCS / MeOHClOMe(E)-1044
Table 3. 13C chemical shifts (ppm) of diethyl (Z)-2,3-dichloro-butenedioate [1] and ethyl methyl (Z)-2,3-dichlorobutenedioate (Z)-4.
Table 3. 13C chemical shifts (ppm) of diethyl (Z)-2,3-dichloro-butenedioate [1] and ethyl methyl (Z)-2,3-dichlorobutenedioate (Z)-4.
Molecules 04 00219 i001C=OC=C
161.17130.50
161.12130.07
161.74130.81
Table 4. 13C chemical shifts (ppm).*
Table 4. 13C chemical shifts (ppm).*
Estimated valuesExp.values
C-3C-2C-3C-2
Molecules 04 00219 i002115.04141.31115.12141.25
115.78140.57115.71140.63
124.49139.95124.54139.82
125.23139.20125.24139.49
* Diethyl (Z)-2-acetoxy-3-bromobutenedioate: 115.47 (C-3) and 141.00 (C-2); Diethyl (Z)-2-acetoxy-3-chlorobutenedioate 124.92 (C-3) and 139.64 (C-2) [1].
Table 5. Products obtained from the ylide 1c.
Table 5. Products obtained from the ylide 1c.
ReagentsXYProductsYield (%)
Cl2ClCl1269
HOBr/AcOHBrOAc1360
NCS/MeOHClOMe1498

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Pinho e Melo, T.M.V.D.; D’A. Rocha Gonsalves, A.M.; Carrapato, S.M.S.; Taborda, A.M.O.M.P. Reactivity of a-Oxophosphonium Ylides: A Contribution to the Mechanistics. Molecules 1999, 4, 219-231. https://doi.org/10.3390/40700219

AMA Style

Pinho e Melo TMVD, D’A. Rocha Gonsalves AM, Carrapato SMS, Taborda AMOMP. Reactivity of a-Oxophosphonium Ylides: A Contribution to the Mechanistics. Molecules. 1999; 4(7):219-231. https://doi.org/10.3390/40700219

Chicago/Turabian Style

Pinho e Melo, Teresa M.V.D., António M. D’A. Rocha Gonsalves, Sara M. S. Carrapato, and Ana M. O. M. P. Taborda. 1999. "Reactivity of a-Oxophosphonium Ylides: A Contribution to the Mechanistics" Molecules 4, no. 7: 219-231. https://doi.org/10.3390/40700219

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