Synthesis of Alkenylgold(I) Complexes Relevant to Catalytic Carboxylative Cyclization of Unsaturated Amines and Alcohols

The carboxylation of unsaturated amine and alcohol compounds, including 4-benzylamino-1-phenyl-1-butyne (homopropargylamine), 2-butyne-1-ol (propargylic alcohol), and 2,3-butadiene-1-ol (allenylmethyl alcohol), using the hydroxidogold(I) complex, AuOH(IPr) [IPr = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene], produces corresponding alkenylgold(I) complexes with a cyclic urethane or carbonate framework in high yields. The reaction takes place in aprotic THF at room temperature under the atmospheric pressure of CO2 in the absence of base additives. The products were characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The functionalized alkenyl complexes prepared from the alkynes can be protonated by treatment with an equimolar amount of acetic acid to afford five- or six-membered carboxylation products, whereas the related alkenyl complex derived from allenylmethyl alcohol decomposed to recover the starting allene via ring-opening decarboxylation.


Introduction
The activation of unsaturated bonds by coordination to a Lewis acidic metal center and the following functionalization have been broadly utilized for catalytic applications.Among the intense research efforts in gold catalysis, a range of addition reactions of nucleophilic functional groups to C-C multiple bonds have been established [1][2][3][4].In this context, organogold intermediates are proposed in mechanistic pathways involving the gold-carbon bond cleavage by a proton (i.e., protodeauration) to generate the products.Synthetic studies on alkenylgold complexes relevant to the gold-promoted transformations of alkynes and allenes have received much interest for gaining insight into catalytic behavior [5][6][7].
Molecules 2024, 29, x FOR PEER REVIEW 2 rather effective for the carboxylative cyclization of 1-(methylamino)-2,3-butadiene (4 lenylmethylamine) using CO2 [12].The superiority of the Ag catalyst over the Au cat corroborates the fact that an isolable alkenylgold complex (5) [12] derived from 4 and showed poor reactivity toward the protonolysis of the alkenyl-metal bond involved in product-releasing step of the catalytic cycle (Scheme 2B).
These results prompted us to explore the feasibility of related alkyne or allene logs for carbonylative cyclization using CO2.The identification of catalytic intermed models via the intramolecular attack of carbamate and carbonate anions to C-C mul bonds is an effective way to gain insight into extending the catalytic carboxylation sys In this paper, we disclose the reaction of several unsaturated amines and alcohols w stoichiometric amount of NHC-gold(I) complex, leading to new alkenylgold comple

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Homopropargylamine
Compared to the synthesis of five-membered cyclic urethanes by the carboxyla cyclization of propargylamines, there are limited examples of the catalytic constructio six-membered variants [13][14][15][16][17][18][19].As a model for 6-exo-dig cyclization, we initially foc on the reactivity of a one-carbon homologated aminoalkyne.Following the synthes alkenylgold(I) complexes from propargylic amines, we performed the reactio homopropargylamine (6) with an equimolar amount of 1 under a CO2 atmosphere in hydrated tetrahydrofuran (THF) at room temperature for 22 h.The desired alkenyl c plex (6) having a six-membered urethane structure was successfully isolated as colo Molecules 2024, 29, x FOR PEER REVIEW 2 rather effective for the carboxylative cyclization of 1-(methylamino)-2,3-butadiene (4 lenylmethylamine) using CO2 [12].The superiority of the Ag catalyst over the Au cat corroborates the fact that an isolable alkenylgold complex (5) [12] derived from 4 and showed poor reactivity toward the protonolysis of the alkenyl-metal bond involved in product-releasing step of the catalytic cycle (Scheme 2B).
These results prompted us to explore the feasibility of related alkyne or allene logs for carbonylative cyclization using CO2.The identification of catalytic intermed models via the intramolecular attack of carbamate and carbonate anions to C-C mul bonds is an effective way to gain insight into extending the catalytic carboxylation sys In this paper, we disclose the reaction of several unsaturated amines and alcohols w stoichiometric amount of NHC-gold(I) complex, leading to new alkenylgold comple

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Homopropargylamine
Compared to the synthesis of five-membered cyclic urethanes by the carboxyla cyclization of propargylamines, there are limited examples of the catalytic constructio six-membered variants [13][14][15][16][17][18][19].As a model for 6-exo-dig cyclization, we initially foc on the reactivity of a one-carbon homologated aminoalkyne.Following the synthes alkenylgold(I) complexes from propargylic amines, we performed the reactio homopropargylamine (6) with an equimolar amount of 1 under a CO2 atmosphere in hydrated tetrahydrofuran (THF) at room temperature for 22 h.The desired alkenyl c plex (6) having a six-membered urethane structure was successfully isolated as colo These results prompted us to explore the feasibility of related alkyne or allene analogs for carbonylative cyclization using CO 2 .The identification of catalytic intermediate models via the intramolecular attack of carbamate and carbonate anions to C-C multiple bonds is an effective way to gain insight into extending the catalytic carboxylation system.In this paper, we disclose the reaction of several unsaturated amines and alcohols with a stoichiometric amount of NHC-gold(I) complex, leading to new alkenylgold complexes.

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Homopropargylamine
Compared to the synthesis of five-membered cyclic urethanes by the carboxylative cyclization of propargylamines, there are limited examples of the catalytic construction of six-membered variants [13][14][15][16][17][18][19].As a model for 6-exo-dig cyclization, we initially focused on the reactivity of a one-carbon homologated aminoalkyne.Following the synthesis of alkenylgold(I) complexes from propargylic amines, we performed the reaction of homopropargylamine (6) with an equimolar amount of 1 under a CO 2 atmosphere in dehydrated tetrahydrofuran (THF) at room temperature for 22 h.The desired alkenyl complex (6) having a six-membered urethane structure was successfully isolated as colorless and thermally stable crystals in 45% yield after recrystallization from a mixed solution of acetone and n-hexane (Scheme 3).and thermally stable crystals in 45% yield after recrystallization from a mixed soluti acetone and n-hexane (Scheme 3).Scheme 3. Synthesis of alkenylgold 7 from 1, homopropargylamine, and CO2.
The alkenylgold complex 7 was fully characterized using NMR spectroscopy mental analysis, and X-ray crystallography.In 13 C{ 1 H} NMR, characteristic signals at and 195.3 ppm were ascribed to the carbene carbon bound to the Au center and the bonyl group derived from CO2, respectively.The chemical shift of 127.9 ppm, attrib to the alkenyl carbon adjacent to the Au center, was reasonable relative to the signa 131.6 and 135.9 ppm for 3a and 3b, respectively, with a five-membered urethane fr work [11].The composition of formal CO2-adduct was also confirmed by CHN elem analysis, as well as the C=O stretching band at 1691 cm -1 in ATR-IR.As shown in Fi 1, the crystallographic structure of 7 revealed that the Au(I) complex adopts a two-co nate geometry with a C-Au-C angle of 172.6(3)°.The C(alkenyl)-Au bond leng 2.056(6) Å is slightly longer than that of 3a and 3b (2.046 and 2.049 Å, respectively) possibly due to the sterically demanding substructure of the six-membered urethane structural data indicate that the carboxylation of 6 provided the anti addition produc the nucleophilic attack of the CO2-derived carbamate moiety on the alkyne coordinat the Au center.We next examined the catalytic version of the carboxylative cyclization of homo pargylic amine.According to the original reaction of propargylamines, 6 was treat methanol under Ar (0.1 MPa) in the presence of 1 with a substrate/catalyst ratio of 50 °C for 15 h; however, a complicated mixture was obtained.By switching the solve toluene, the corresponding cyclic urethane was obtained as the 6-exo-dig cyclization p uct in 28% yield and 22% of the unreacted substrate still remained in the reaction mix Due to a low catalytic activity of the Au complex, the carboxylation could not be pleted even under pressurized CO2 (3.0 MPa).The alkenylgold complex 7 was fully characterized using NMR spectroscopy, elemental analysis, and X-ray crystallography.In 13 C{ 1 H} NMR, characteristic signals at 153.1 and 195.3 ppm were ascribed to the carbene carbon bound to the Au center and the carbonyl group derived from CO 2 , respectively.The chemical shift of 127.9 ppm, attributed to the alkenyl carbon adjacent to the Au center, was reasonable relative to the signals at 131.6 and 135.9 ppm for 3a and 3b, respectively, with a five-membered urethane framework [11].The composition of formal CO 2 -adduct was also confirmed by CHN elemental analysis, as well as the C=O stretching band at 1691 cm -1 in ATR-IR.As shown in Figure 1, the crystallographic structure of 7 revealed that the Au(I) complex adopts a two-coordinate geometry with a C-Au-C angle of 172.6(3) • .The C(alkenyl)-Au bond length of 2.056(6) Å is slightly longer than that of 3a and 3b (2.046 and 2.049 Å, respectively) [11], possibly due to the sterically demanding substructure of the six-membered urethane.The structural data indicate that the carboxylation of 6 provided the anti addition product via the nucleophilic attack of the CO 2 -derived carbamate moiety on the alkyne coordinated to the Au center.
The alkenylgold complex 7 was fully characterized using NMR spectroscopy, mental analysis, and X-ray crystallography.In 13 C{ 1 H} NMR, characteristic signals at 1 and 195.3 ppm were ascribed to the carbene carbon bound to the Au center and the bonyl group derived from CO2, respectively.The chemical shift of 127.9 ppm, attribu to the alkenyl carbon adjacent to the Au center, was reasonable relative to the signa 131.6 and 135.9 ppm for 3a and 3b, respectively, with a five-membered urethane fra work [11].The composition of formal CO2-adduct was also confirmed by CHN eleme analysis, as well as the C=O stretching band at 1691 cm -1 in ATR-IR.As shown in Fig 1, the crystallographic structure of 7 revealed that the Au(I) complex adopts a two-coo nate geometry with a C-Au-C angle of 172.6(3)°.The C(alkenyl)-Au bond lengt 2.056(6) Å is slightly longer than that of 3a and 3b (2.046 and 2.049 Å, respectively) possibly due to the sterically demanding substructure of the six-membered urethane.structural data indicate that the carboxylation of 6 provided the anti addition produc the nucleophilic attack of the CO2-derived carbamate moiety on the alkyne coordinate the Au center.We next examined the catalytic version of the carboxylative cyclization of homo pargylic amine.According to the original reaction of propargylamines, 6 was treate methanol under Ar (0.1 MPa) in the presence of 1 with a substrate/catalyst ratio of 50 a °C for 15 h; however, a complicated mixture was obtained.By switching the solven toluene, the corresponding cyclic urethane was obtained as the 6-exo-dig cyclization p uct in 28% yield and 22% of the unreacted substrate still remained in the reaction mixt Due to a low catalytic activity of the Au complex, the carboxylation could not be c pleted even under pressurized CO2 (3.0 MPa).We next examined the catalytic version of the carboxylative cyclization of homopropargylic amine.According to the original reaction of propargylamines, 6 was treated in methanol under Ar (0.1 MPa) in the presence of 1 with a substrate/catalyst ratio of 50 at 40 • C for 15 h; however, a complicated mixture was obtained.By switching the solvent to toluene, the corresponding cyclic urethane was obtained as the 6-exo-dig cyclization product in 28% yield and 22% of the unreacted substrate still remained in the reaction mixture.Due to a low catalytic activity of the Au complex, the carboxylation could not be completed even under pressurized CO 2 (3.0 MPa).

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Propargy Alcohol
The carboxylative cyclization of propargylic alcohols has also been investigated using metal and base catalysts.In most catalytic systems, tertiary alcohols have been exclusively used as the substrates, whereas few examples have been reported for the synthesis of cyclic carbonate from primary propargylic alcohol [20][21][22][23].In light of the potential for expanding the substrate scope, we next explore the synthesis of alkenylgold from CO 2 and 2-butyne-1-ol (8) without the virtue of the Thorpe-Ingold effect.When stoichiometric carboxylative cyclization was performed by the treatment of 1 with 8 in THF under a CO 2 atmosphere for 1 h, the desired alkenylgold complex (9) was formed and successfully isolated in 80% yield after recrystallization (Scheme 4).The 13 C{ 1 H} NMR spectrum in CDCl 3 displayed a carbonate resonance at 155.7 ppm, along with a signal at 195.8 ppm ascribed to the carbene carbon bound to the Au center.Two alkenyl carbon signals observed at 131.7 and 139.0 ppm were identical to those at 131.6 and 139.6 ppm for the carbamate analog 3a derived from 1-(methylamino)-2-butyne.

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Proparg
The carboxylative cyclization of propargylic alcohols has also been investig metal and base catalysts.In most catalytic systems, tertiary alcohols have been used as the substrates, whereas few examples have been reported for the synt clic carbonate from primary propargylic alcohol [20][21][22][23].In light of the poten panding the substrate scope, we next explore the synthesis of alkenylgold fro 2-butyne-1-ol (8) without the virtue of the Thorpe-Ingold effect.When stoichio boxylative cyclization was performed by the treatment of 1 with 8 in THF u atmosphere for 1 h, the desired alkenylgold complex (9) was formed and succe lated in 80% yield after recrystallization (Scheme 4).The 13 C{ 1 H} NMR spectru displayed a carbonate resonance at 155.7 ppm, along with a signal at 195.8 pp to the carbene carbon bound to the Au center.Two alkenyl carbon signals o 131.7 and 139.0 ppm were identical to those at 131.6 and 139.6 ppm for the analog 3a derived from 1-(methylamino)-2-butyne.A single-crystal X-ray diffraction analysis revealed that the structure of 9 that of the monomeric alkenylgold complex of 3a, as shown in Figure 2. The bo and angles within the alkenyl ligand (Table S2) were roughly similar to those thane analog 3a [11].The sum of angles around each alkene carbon atom is cons a planar geometry of the alkenyl ligand.A comparable distance (1.432(5) Å) b alkenyl carbon atom at the β-position to the Au center and the carbonate ox originated from CO2 was identified, relative to the corresponding bond length (mean value) in the carbamate derivative of 3a [11].These results are indica smooth capture of CO2 at the alcoholic moiety followed by nucleophilic cycliza struct the five-membered carbonate ring.A single-crystal X-ray diffraction analysis revealed that the structure of 9 resembles that of the monomeric alkenylgold complex of 3a, as shown in Figure 2. The bond lengths and angles within the alkenyl ligand (Table S2) were roughly similar to those of the urethane analog 3a [11].The sum of angles around each alkene carbon atom is consistent with a planar geometry of the alkenyl ligand.A comparable distance (1.432(5) Å) between the alkenyl carbon atom at the β-position to the Au center and the carbonate oxygen atom originated from CO 2 was identified, relative to the corresponding bond length of 1.437 Å (mean value) in the carbamate derivative of 3a [11].These results are indicative of the smooth capture of CO 2 at the alcoholic moiety followed by nucleophilic cyclization to construct the five-membered carbonate ring.

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Propargy Alcohol
The carboxylative cyclization of propargylic alcohols has also been investigated using metal and base catalysts.In most catalytic systems, tertiary alcohols have been exclusively used as the substrates, whereas few examples have been reported for the synthesis of cyclic carbonate from primary propargylic alcohol [20][21][22][23].In light of the potential for expanding the substrate scope, we next explore the synthesis of alkenylgold from CO2 and 2-butyne-1-ol (8) without the virtue of the Thorpe-Ingold effect.When stoichiometric carboxylative cyclization was performed by the treatment of 1 with 8 in THF under a CO2 atmosphere for 1 h, the desired alkenylgold complex (9) was formed and successfully isolated in 80% yield after recrystallization (Scheme 4).The 13 C{ 1 H} NMR spectrum in CDCl3 displayed a carbonate resonance at 155.7 ppm, along with a signal at 195.8 ppm ascribed to the carbene carbon bound to the Au center.Two alkenyl carbon signals observed at 131.7 and 139.0 ppm were identical to those at 131.6 and 139.6 ppm for the carbamate analog 3a derived from 1-(methylamino)-2-butyne.A single-crystal X-ray diffraction analysis revealed that the structure of 9 resembles that of the monomeric alkenylgold complex of 3a, as shown in Figure 2. The bond lengths and angles within the alkenyl ligand (Table S2) were roughly similar to those of the urethane analog 3a [11].The sum of angles around each alkene carbon atom is consistent with a planar geometry of the alkenyl ligand.A comparable distance (1.432(5) Å) between the alkenyl carbon atom at the β-position to the Au center and the carbonate oxygen atom originated from CO2 was identified, relative to the corresponding bond length of 1.437 Å (mean value) in the carbamate derivative of 3a [11].These results are indicative of the smooth capture of CO2 at the alcoholic moiety followed by nucleophilic cyclization to construct the five-membered carbonate ring.In the trial catalytic carbonate synthesis from 8 and CO 2 (5.0 MPa) with reference to the carboxylative cyclization of propargylic amines [10], the alcoholic substrate was mostly recovered from the reaction mixture containing a catalytic amount of 9 in methanol even after an elongated reaction time of 48 h.The alcohol, unlike unsaturated amines, was less susceptible to the catalytic release of cyclic carbonate, while the basicity of hydroxidogold complex possibly contributes to enhancing the nucleophilicity of propargylic alcohols for carboxylation.

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Allenylmethyl Alcohol
The carboxylative cyclization of allenylated alcohols has not been reported (related cyclic carbonate synthesis from allenyl alcohols and CO 2 via Mizoroki-Heck type reaction was reported by Inoue, et al., as cited in ref. [24]), whereas allenylmethylamine has successfully been converted into corresponding cyclic urethane.To investigate nucleophilic attack on the carbon-carbon double bond by a carbonate moiety generated from CO 2 , we next focused on the reaction of allenylmethyl alcohol (10).In a similar manner to the synthesis of 7 and 9, the reaction of 1 and 10 proceeded in THF under CO 2 (5.0 MPa) at room temperature to give a colorless solution.After the evaporation of the solvent, the desired alkenylgold complex (11) having a cyclic carbonate structure was isolated in 76% yield as crystals which were formed by slow diffusion of n-pentane into the solution in acetone (Scheme 5).
In the trial catalytic carbonate synthesis from 8 and CO2 (5.0 MPa) with r the carboxylative cyclization of propargylic amines [10], the alcoholic sub mostly recovered from the reaction mixture containing a catalytic amount of 9 i even after an elongated reaction time of 48 h.The alcohol, unlike unsaturated a less susceptible to the catalytic release of cyclic carbonate, while the basicity idogold complex possibly contributes to enhancing the nucleophilicity of pro cohols for carboxylation.

Synthesis and Characterization of Alkenylgold(I) Complex Derived from Allenylm Alcohol
The carboxylative cyclization of allenylated alcohols has not been repor cyclic carbonate synthesis from allenyl alcohols and CO2 via Mizoroki-Heck ty was reported by Inoue, et al., as cited in ref. [24]), whereas allenylmethylami cessfully been converted into corresponding cyclic urethane.To investigate n attack on the carbon-carbon double bond by a carbonate moiety generated fro next focused on the reaction of allenylmethyl alcohol (10).In a similar manner thesis of 7 and 9, the reaction of 1 and 10 proceeded in THF under CO2 (5.0 M temperature to give a colorless solution.After the evaporation of the solvent, alkenylgold complex (11) having a cyclic carbonate structure was isolated in 7 crystals which were formed by slow diffusion of n-pentane into the solution (Scheme 5).The product was characterized by NMR spectroscopy, elemental analysis crystallography.In the 1 H NMR spectrum of 11 in CDCl3, the unsymmetrical t nyl protons appeared as double doublet signals at 4.61 and 5.47 ppm with 2 J couplings, which is comparable to those at 4.46 and 5.35 ppm for the alkenylgo 5 [12] synthesized from allenylmethylamine.Compared to the alkenylgold marked downfield shift of the 13 C{ 1 H} NMR signal to 172.0 ppm, which was the alkenyl carbon adjacent to the Au center, was observed, as with the case ppm) having a cyclic urethane framework.The carbonate signal appeared at 1 a similar manner to that of 9 (155.7 ppm).In addition, the carbonate functio firmed by a C=O stretching frequency at 1782 cm -1 in ATR-IR.As shown in Fig X-ray crystallographic structure shows a typical two-coordinate geometry aro center attached to the NHC carbene and alkenyl carbons.The distance betw carbons (1.322(6) Å) is close to that of other alkenyl complexes including th (1.321(5) Å).Other bond lengths and angles within the alkenyl ligand (Tab roughly similar to those of the urethane analog 5 [12].Apart from the alkenyl (3a, 3b, 5, 7, and 9) displaying similar structures where the urethane or carbona the NHC ligand lie in the nearly same plane, the carbonate ring and double alkenyl ligand in 11 are perpendicular to the NHC ring, as illustrated in Figur The product was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography.In the 1 H NMR spectrum of 11 in CDCl 3 , the unsymmetrical terminal vinyl protons appeared as double doublet signals at 4.61 and 5.47 ppm with 2 J HH and 4 J HH couplings, which is comparable to those at 4.46 and 5.35 ppm for the alkenylgold complex 5 [12] synthesized from allenylmethylamine.Compared to the alkenylgold isomer 9, a marked downfield shift of the 13 C{ 1 H} NMR signal to 172.0 ppm, which was assigned to the alkenyl carbon adjacent to the Au center, was observed, as with the case of 5 (175.4ppm) having a cyclic urethane framework.The carbonate signal appeared at 156.1 ppm in a similar manner to that of 9 (155.7 ppm).In addition, the carbonate function was confirmed by a C=O stretching frequency at 1782 cm -1 in ATR-IR.As shown in Figure 3a, the X-ray crystallographic structure shows a typical two-coordinate geometry around the Au center attached to the NHC carbene and alkenyl carbons.The distance between alkene carbons (1.322(6) Å) is close to that of other alkenyl complexes including the isomer 9 (1.321(5)Å).Other bond lengths and angles within the alkenyl ligand (Table S3) were roughly similar to those of the urethane analog 5 [12].Apart from the alkenyl complexes (3a, 3b, 5, 7, and 9) displaying similar structures where the urethane or carbonate ring and the NHC ligand lie in the nearly same plane, the carbonate ring and double bond of the alkenyl ligand in 11 are perpendicular to the NHC ring, as illustrated in Figure 3b.

Protonolysis of Alkenylgold Complexes 7, 9, and 11
Alkenylgold complexes produce corresponding alkenes via the protodeauration step in catalysis [25][26][27].For example, the complexes 2a and 2b produced corresponding urethanes via protonolysis and showed catalytic reactivity in the carboxylative cyclization of propargylamines.Therefore, we tested the protonolysis of the obtained alkenylgold complexes as the models of the new catalytic carboxylative cyclizations.NMR monitoring experiments by the treatment of 7 or 9 with an equimolar amount of acetic acid (pKa = 4.76 in H 2 O) in CDCl 3 showed that the protodeauration proceeded to yield only Z products (7-H and 9-H) quantitatively (Scheme 6).Contrastingly, the reaction of 11 with acetic acid produced the parent allenyl alcohol 10 and Au(OCOCH 3 )(IPr) readily and quantitatively via ring opening and decarboxylation, owing to the relatively weak C-O bond in the allylic carbonate.

Protonolysis of Alkenylgold Complexes 7, 9, and 11
Alkenylgold complexes produce corresponding alkenes via the protodeauration in catalysis [25][26][27].For example, the complexes 2a and 2b produced corresponding thanes via protonolysis and showed catalytic reactivity in the carboxylative cyclizatio propargylamines.Therefore, we tested the protonolysis of the obtained alkenylgold c plexes as the models of the new catalytic carboxylative cyclizations.NMR monitoring periments by the treatment of 7 or 9 with an equimolar amount of acetic acid (pKa = in H2O) in CDCl3 showed that the protodeauration proceeded to yield only Z product H and 9-H) quantitatively (Scheme 6).Contrastingly, the reaction of 11 with acetic produced the parent allenyl alcohol 10 and Au(OCOCH3)(IPr) readily and quantitati via ring opening and decarboxylation, owing to the relatively weak C-O bond in th lylic carbonate.Scheme 6. Protonolysis of alkenylgold complexes 7, 9, and 11.

Protonolysis of Alkenylgold Complexes 7, 9, and 11
Alkenylgold complexes produce corresponding alkenes via the protodeauration in catalysis [25][26][27].For example, the complexes 2a and 2b produced corresponding thanes via protonolysis and showed catalytic reactivity in the carboxylative cyclizatio propargylamines.Therefore, we tested the protonolysis of the obtained alkenylgold c plexes as the models of the new catalytic carboxylative cyclizations.NMR monitorin periments by the treatment of 7 or 9 with an equimolar amount of acetic acid (pKa = in H2O) in CDCl3 showed that the protodeauration proceeded to yield only Z produc H and 9-H) quantitatively (Scheme 6).Contrastingly, the reaction of 11 with acetic produced the parent allenyl alcohol 10 and Au(OCOCH3)(IPr) readily and quantitat via ring opening and decarboxylation, owing to the relatively weak C-O bond in th lylic carbonate.

Materials and Methods
All syntheses were performed under a purified argon atmosphere using stan Schlenk techniques.2-Butyn-1-ol (8) was purchased from Tokyo Chemical Industry

Protonolysis of the Alkenylgold Complexes with Acetic Acid
An NMR tube equipped with a J-Young valve was charged with alkenylgold complex (10 µmol), durene and CDCl 3 (0.5 mL), and acetic acid (10 µmol) was added to the solution.The reaction was monitored via 1 H NMR spectroscopy at room temperature.

X-ray Crystal Structure Determination
Diffraction experiments were performed on a Rigaku Saturn CCD area detector (Rigaku Corporation, Tokyo, Japan) using graphite-monochromated Mo-Kα radiation (λ = 0.71075 Å) under a nitrogen stream at 193 K. Single crystals suitable for X-ray analyses were mounted on glass fibers.The crystal-to-detector distance was 45.0 mm.Data were collected to a maximum 2θ value of 55.0 • .A total of 720 oscillation images were collected.A sweep of the data was carried out by using ω scans from −110.0 to 70.0 • in 0.5 • steps at χ = 45.0 • and ϕ = 0.0 • .A second sweep was performed by using ω scans from −110.0 to 70.0 • in 0.5 • steps at χ = 45.0 • and ϕ = 90.0• .Intensity data were collected for Lorentzpolarization effects and absorption.Details of the crystal and data collection parameters for the compounds 7, 9, and 11 are summarized in Table S1.The structure solution and refinements were performed with the CrystalStructure program package [31].The heavy atom positions were determined by a direct program method (SIR92) [32] and the remaining non-hydrogen atoms were found by subsequent Fourier syntheses and were refined by full-matrix least-squares techniques against F 2 using the SHELXL-2014/7 program [33].The hydrogen atoms were placed at calculated positions and were refined with a riding model.These crystallographic data have been deposited with Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC-2339858 (7), CCDC-2339859 (9), and CCDC-2339860 (11).

Conclusions
Functionalized alkenylgold(I) complexes can be versatilely synthesized by the reaction of AuOH(IPr) and unsaturated amines or alcohols under a CO 2 atmosphere.The isolated complexes are regarded as possible catalytic intermediates for the carboxylative cyclization using CO 2 .The feasibility of this method for Au catalysis can be evaluated by performing protonolysis, which is the fundamental process in catalytic carboxylative cyclization.The carboxylative cyclizations of homopropargylamine and primary propargylic alcohol were demonstrated by stepwise stoichiometric carboxyauration and protonolysis.Based on these fundamental aspects on the catalytic carboxylative cyclizations, further investigations involving the transformation of the related alkynes and alkenes are now underway.

Figure 1 .
Figure 1.X-ray crystal structure of 7. The hydrogen atoms are omitted for clarity.Thermal ellip are shown at the 30% probability level.

Figure 1 .
Figure 1.X-ray crystal structure of 7. The hydrogen atoms are omitted for clarity.Thermal ellips are shown at the 30% probability level.

Figure 1 .
Figure 1.X-ray crystal structure of 7. The hydrogen atoms are omitted for clarity.Thermal ellipsoids are shown at the 30% probability level.

Figure 2 .Figure 2 .
Figure 2. X-ray crystal structure of 9.The hydrogen atoms are omitted for clarity.Thermal ellipsoids are shown at the 30% probability level.

Figure 3 .
Figure 3. X-ray crystal structure of 11.The hydrogen atoms are omitted for clarity.Thermal soids are shown at the 30% probability level.

Figure 3 .
Figure 3. X-ray crystal structure of 11.The hydrogen atoms are omitted for clarity.Thermal ellipsoids are shown at the 30% probability level.

Figure 3 .
Figure 3. X-ray crystal structure of 11.The hydrogen atoms are omitted for clarity.Thermal soids are shown at the 30% probability level.