Syntheses of Arylphosphonium Salts from Cyclotrimerization of Terminal Aryl Alknyes by a Ruthenium Pentadienyl Complex and Revisiting the Catalytic Dimerization

The synthesis of polyaryl phosphonium salts by cyclotrimerization of aryl alkynes is induced by a stoichiometric amount of the ruthenium η⁵-pentadienyl complex (η⁵-C₅H₇)­(PPh₃)₂RuCl (<b>1</b>). With only 1 mol % quantity, complex <b>1</b> efficiently catalyzed the dimerization of aryl alkynes at room temperature to afford the corresponding (<i>Z</i>)-1,4-diarylbut-1-en-3-yne derivatives as the major products

Syntheses of Arylphosphonium Salts from Cyclotrimerization of Terminal Aryl Alknyes by a Ruthenium Pentadienyl Complex and Revisiting the Catalytic Dimerization

The synthesis of polyaryl phosphonium salts by cyclotrimerization of aryl alkynes is induced by a stoichiometric amount of the ruthenium η⁵-pentadienyl complex (η⁵-C₅H₇)­(PPh₃)₂RuCl (<b>1</b>). With only 1 mol % quantity, complex <b>1</b> efficiently catalyzed the dimerization of aryl alkynes at room temperature to afford the corresponding (<i>Z</i>)-1,4-diarylbut-1-en-3-yne derivatives as the major products

Highly Enantioselective 3-Furylation of Ketones Using (3-Furyl)titanium Nucleophile

A novel asymmetric 3-furyl addition of (3-furyl)Ti(OiPr)3 to ketones in the presence of 10 mol % (S)-BINOL is reported. The catalytic system works excellently for aromatic ketones, α- or β-halophenones, α,β-unsaturated ketones, and acetylfuran, affording products in high yields with excellent enantioselectivities of up to 97% ee

Highly Enantioselective 3-Furylation of Ketones Using (3-Furyl)titanium Nucleophile

A novel asymmetric 3-furyl addition of (3-furyl)Ti(OiPr)3 to ketones in the presence of 10 mol % (S)-BINOL is reported. The catalytic system works excellently for aromatic ketones, α- or β-halophenones, α,β-unsaturated ketones, and acetylfuran, affording products in high yields with excellent enantioselectivities of up to 97% ee

Highly Enantioselective 3-Furylation of Ketones Using (3-Furyl)titanium Nucleophile

A novel asymmetric 3-furyl addition of (3-furyl)Ti(OiPr)3 to ketones in the presence of 10 mol % (S)-BINOL is reported. The catalytic system works excellently for aromatic ketones, α- or β-halophenones, α,β-unsaturated ketones, and acetylfuran, affording products in high yields with excellent enantioselectivities of up to 97% ee

Synthesis, Structures, and Characterizations of [ArTi(O-<i>i</i>-Pr)₃]₂ and Efficient Room-Temperature Aryl−Aryl Coupling of Aryl Bromides with [ArTi(O-<i>i</i>-Pr)₃]₂ Catalyzed by the Economic Pd(OAc)₂/PCy₃ System

The series of aryltris(2-propoxo)titanium reagents [ArTi(O-i-Pr)3]2 (Ar = Ph (1a), 2-MeC6H4 (1b), 4-MeC6H4 (1c), 4-ClC6H4 (1d), 4-TMSC6H4 (1e), 4-CF3C6H4 (1f), 3,5-Me2C6H3 (1g)) was synthesized from reactions of the in situ prepared ClTi(O-i-Pr)3 with ArMgBr in THF. All compounds were characterized by NMR spectroscopy and elemental analyses. A variable-temperature 1H NMR study of 1c suggested that compounds 1 are dimeric species in solution. The structures of complexes 1b,g were further determined by single-crystal X-ray analyses. X-ray diffraction studies confirmed that the aryltris(2-propoxo)titanium complexes have a dimeric structure with a Ti2O2 core bridging through the oxygen atom of two 2-propoxide groups. The application of aryltris(2-propoxo)titanium reagents to cross-coupling with aryl bromides catalyzed by the catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 was studied. Results show that aryltris(2-propoxo)titanium compounds are excellent reagents for aryl−aryl coupling reactions at room temperature and that the system works well for a wide range of aryl bromides regardless of the electronic or steric nature of the substituents on the aryl bromides. Couplings with pyridyl bromides under the mild reaction condition of room temperature were also demonstrated to afford products in high yields over 2−3 h. It is worth noting that couplings with 3,3′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene proceeded smoothly also at room temperature over 3−5 h, affording products in excellent yields. The coupling reactions demonstrated in this study are highly efficient compared to the typical synthesis of 3,3′-diaryl-2,2′-dimethoxy-1,1′-binaphthylenes via Suzuki couplings, which required higher catalyst loading under reaction conditions of longer reaction times (18−24 h in general) at elevated temperatures

Synthesis, Structures, and Characterizations of [ArTi(O-<i>i</i>-Pr)₃]₂ and Efficient Room-Temperature Aryl−Aryl Coupling of Aryl Bromides with [ArTi(O-<i>i</i>-Pr)₃]₂ Catalyzed by the Economic Pd(OAc)₂/PCy₃ System

The series of aryltris(2-propoxo)titanium reagents [ArTi(O-i-Pr)3]2 (Ar = Ph (1a), 2-MeC6H4 (1b), 4-MeC6H4 (1c), 4-ClC6H4 (1d), 4-TMSC6H4 (1e), 4-CF3C6H4 (1f), 3,5-Me2C6H3 (1g)) was synthesized from reactions of the in situ prepared ClTi(O-i-Pr)3 with ArMgBr in THF. All compounds were characterized by NMR spectroscopy and elemental analyses. A variable-temperature 1H NMR study of 1c suggested that compounds 1 are dimeric species in solution. The structures of complexes 1b,g were further determined by single-crystal X-ray analyses. X-ray diffraction studies confirmed that the aryltris(2-propoxo)titanium complexes have a dimeric structure with a Ti2O2 core bridging through the oxygen atom of two 2-propoxide groups. The application of aryltris(2-propoxo)titanium reagents to cross-coupling with aryl bromides catalyzed by the catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 was studied. Results show that aryltris(2-propoxo)titanium compounds are excellent reagents for aryl−aryl coupling reactions at room temperature and that the system works well for a wide range of aryl bromides regardless of the electronic or steric nature of the substituents on the aryl bromides. Couplings with pyridyl bromides under the mild reaction condition of room temperature were also demonstrated to afford products in high yields over 2−3 h. It is worth noting that couplings with 3,3′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene proceeded smoothly also at room temperature over 3−5 h, affording products in excellent yields. The coupling reactions demonstrated in this study are highly efficient compared to the typical synthesis of 3,3′-diaryl-2,2′-dimethoxy-1,1′-binaphthylenes via Suzuki couplings, which required higher catalyst loading under reaction conditions of longer reaction times (18−24 h in general) at elevated temperatures

Synthesis, Structures, and Characterizations of [ArTi(O-<i>i</i>-Pr)₃]₂ and Efficient Room-Temperature Aryl−Aryl Coupling of Aryl Bromides with [ArTi(O-<i>i</i>-Pr)₃]₂ Catalyzed by the Economic Pd(OAc)₂/PCy₃ System

The series of aryltris(2-propoxo)titanium reagents [ArTi(O-i-Pr)3]2 (Ar = Ph (1a), 2-MeC6H4 (1b), 4-MeC6H4 (1c), 4-ClC6H4 (1d), 4-TMSC6H4 (1e), 4-CF3C6H4 (1f), 3,5-Me2C6H3 (1g)) was synthesized from reactions of the in situ prepared ClTi(O-i-Pr)3 with ArMgBr in THF. All compounds were characterized by NMR spectroscopy and elemental analyses. A variable-temperature 1H NMR study of 1c suggested that compounds 1 are dimeric species in solution. The structures of complexes 1b,g were further determined by single-crystal X-ray analyses. X-ray diffraction studies confirmed that the aryltris(2-propoxo)titanium complexes have a dimeric structure with a Ti2O2 core bridging through the oxygen atom of two 2-propoxide groups. The application of aryltris(2-propoxo)titanium reagents to cross-coupling with aryl bromides catalyzed by the catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 was studied. Results show that aryltris(2-propoxo)titanium compounds are excellent reagents for aryl−aryl coupling reactions at room temperature and that the system works well for a wide range of aryl bromides regardless of the electronic or steric nature of the substituents on the aryl bromides. Couplings with pyridyl bromides under the mild reaction condition of room temperature were also demonstrated to afford products in high yields over 2−3 h. It is worth noting that couplings with 3,3′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene proceeded smoothly also at room temperature over 3−5 h, affording products in excellent yields. The coupling reactions demonstrated in this study are highly efficient compared to the typical synthesis of 3,3′-diaryl-2,2′-dimethoxy-1,1′-binaphthylenes via Suzuki couplings, which required higher catalyst loading under reaction conditions of longer reaction times (18−24 h in general) at elevated temperatures

Domino Cyclization of 1,<i>n</i>‑Enynes (<i>n</i> = 7, 8, 9) Giving Derivatives of Pyrane, Chromene, Fluorene, Phenanthrene and Dibenzo[7]annulene by Ruthenium Complexes

Cyclization of the ether enyne <b>1</b> catalyzed by [Ru]­NCCH₃⁺ ([Ru] = Cp­(PPh₃)₂Ru) in CHCl₃ generates a diastereomeric mixture of the substituted tetrahydropyran <b>11</b>. Presumably, formation of an allenylidene complex is followed by a cyclization by nucleophilic addition of the olefinic group to Cγ of the ligand giving a boat-like six-membered ring. The diastereoselectivity is controlled by the 1,3-diaxial interaction. The vinylidene complex <b>7</b>, a precursor of <b>11</b>, is obtained from <b>1</b> and [Ru]­Cl. In a mixture of MeOH/CHCl₃, the domino cyclization of <b>1</b> further affords <b>14a</b>, a chromene product catalytically. The second cyclization proceeds via nucleophilic addition of the resulting olefinic unit to Cα of <b>7</b>. But the ether enyne <b>3</b> with a cyclopentyl ring on the olefinic unit undergoes only single cyclization due to steric effect. The propargyl alcohol and the two terminal methyl groups on the olefinic unit shape the cyclization. Thus, similar all-carbon 1,<i>n</i>-enynes (<i>n</i> = 7, 8, 9) <b>4</b>–<b>6</b> each with an aromatic linker undergo direct domino cyclization catalyzed by [Ru]­NCCH₃⁺, to give derivatives of tricyclic fluorene, phenanthrene and dibenzo[7]­annulene, respectively, with no intermediate observed

Domino Cyclization of 1,<i>n</i>‑Enynes (<i>n</i> = 7, 8, 9) Giving Derivatives of Pyrane, Chromene, Fluorene, Phenanthrene and Dibenzo[7]annulene by Ruthenium Complexes

Cyclization of the ether enyne <b>1</b> catalyzed by [Ru]­NCCH₃⁺ ([Ru] = Cp­(PPh₃)₂Ru) in CHCl₃ generates a diastereomeric mixture of the substituted tetrahydropyran <b>11</b>. Presumably, formation of an allenylidene complex is followed by a cyclization by nucleophilic addition of the olefinic group to Cγ of the ligand giving a boat-like six-membered ring. The diastereoselectivity is controlled by the 1,3-diaxial interaction. The vinylidene complex <b>7</b>, a precursor of <b>11</b>, is obtained from <b>1</b> and [Ru]­Cl. In a mixture of MeOH/CHCl₃, the domino cyclization of <b>1</b> further affords <b>14a</b>, a chromene product catalytically. The second cyclization proceeds via nucleophilic addition of the resulting olefinic unit to Cα of <b>7</b>. But the ether enyne <b>3</b> with a cyclopentyl ring on the olefinic unit undergoes only single cyclization due to steric effect. The propargyl alcohol and the two terminal methyl groups on the olefinic unit shape the cyclization. Thus, similar all-carbon 1,<i>n</i>-enynes (<i>n</i> = 7, 8, 9) <b>4</b>–<b>6</b> each with an aromatic linker undergo direct domino cyclization catalyzed by [Ru]­NCCH₃⁺, to give derivatives of tricyclic fluorene, phenanthrene and dibenzo[7]­annulene, respectively, with no intermediate observed