9 research outputs found

    Sequential Allenylidene/Vinylidene Cyclization for Stereoselective Construction of Bicyclic Carbocycles from Propargyl Alcohol

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    Consecutive cyclization reactions of phenyl propargyl alcohols <b>1</b> and <b>2</b> are catalyzed by [Ru]NCCH<sub>3</sub><sup>+</sup> ([Ru] = Cp(PPh<sub>3</sub>)<sub>2</sub>Ru) in cosolvent CHCl<sub>3</sub>/MeOH at 60 °C, to afford the fused cyclic compounds <b>11a</b> (R = Me) and <b>10a</b> (R = Me), respectively

    Sequential Allenylidene/Vinylidene Cyclization for Stereoselective Construction of Bicyclic Carbocycles from Propargyl Alcohol

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    Consecutive cyclization reactions of phenyl propargyl alcohols 1 and 2 are catalyzed by [Ru]NCCH3+ ([Ru] = Cp(PPh3)2Ru) in cosolvent CHCl3/MeOH at 60 °C, to afford the fused cyclic compounds 11a (R = Me) and 10a (R = Me), respectively

    Tandem Cyclization in Ruthenium Vinylidene Complexes with Two Ester Groups

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    The reaction of [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) with o-ethynyl-substituted methyl benzoate, followed by a sequential deprotonation and electrophilic alkylation reactions by further reacting with base and various alkyl haloacetates, respectively, generated several disubstituted ruthenium vinylidene complexes. In the deprotonation reactions of these disubstituted vinylidene complexes containing two ester groups, tandem cyclizations of the ligand is accompanied with a methanol elimination to generate a new organometallic product containing a three-ring indenofuranone ligand, which structure has been confirmed by a single-crystal X-ray diffraction analysis. Facile protonation and methylation are observed in these indenofuranone complexes. Additionally, for the simple furyl complex containing an O-benzyl group, a 1,3-migration of the benzyl group is observed to yield a lactone product and a Claisen rearrangement is also observed in analogous complexes with O-allyl or O-propargyl groups

    Cyclization Accompanied with 1,2-Phenyl Migration in the Protonation of Ruthenium Acetylide Complex Containing an Allenyl Group

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    Reaction of the ruthenium allenylidene complex [Ru]CCCPh2 (1, [Ru] = Cp(PPh3)2Ru) with the propargylic Grignard reagent R-CCCH2MgBr (R = CH3, CH2CH3, Ph) yielded a mixture of two acetylide complexes. The major products, [Ru]CCCPh2C(R)CCH2 (2a, R = CH3; 2b, R = CH2CH3; 2c, R = Ph), have an allenyne moiety, and the minor ones, [Ru]CCCPh2CH2CCR (3a, R = CH3; 3b, R = CH2CH3; 3c, R = Ph), have a diyne ligand. The reaction of similar propargyl Grignard reagent HCCCH2MgBr with 1 yielded only the diyne complex 3d. Treatment of complexes 2a−2c with HBF4 afforded the cyclization complexes 5a−5c, respectively, proceeding via a vinylidene intermediate. The cyclization of the allenyl and the vinylidene groups is accompanied with a phenyl group migration. Complex 5b is fully characterized by a single-crystal X-ray diffraction analysis. Similar cyclization of complexes 2a and 2b, catalyzed by a Au phosphine complex, gave the ruthenium vinylidene complexes 6a and 6b, respectively, with different selectivity from that of the protonation reaction. Au-catalyzed cyclization of the diyne complex 3d yielded 6d, which is fully characterized by a single-crystal X-ray diffraction analysis

    Carbon−Carbon Bond Formation Involving a Vinylidene Ligand and Ferrocenyl Substituent in Cationic Ruthenium Complexes

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    A formal intramolecular olefin metathesis process between the CC double bond of a vinylidene ligand and a pendant vinyl group in several ruthenium complexes, each with a ferrocenyl group, is followed by an additional intramolecular C−C bond formation between a Cp ligand of the ferrocenyl substituent and the vinylidene ligand. The regioselectivity of the C−C bond formation reaction at either the substituted or the nonsubstituted Cp group of the ferrocenyl group is possibly influenced by a steric effect between the neighboring substituent near the ferrocenyl group and the phosphine ligand on the ruthenium metal center. The structure of one ruthenium complex resulting from such a C−C bond formation has been fully characterized by a single-crystal X-ray diffraction analysis

    Intramolecular Diels−Alder Reactions in Ruthenium Vinylidene Complexes Containing Anthracenyl Groups

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    An intramolecular Diels−Alder (IMDA) reaction was observed at room temperature between an allyl group and a chloroanthracenyl group that were both bonded to the vinylidene ligand of the cationic ruthenium complex [Ru]CC(CH2CHCH2)CH(CH2CHCH2)(C14H8Cl)+ (6; [Ru] = Cp(PPh3)3Ru). The vinylidene ligand functions as a mediator to bring the allyl and the chloroanthracenyl groups in proximity for the reaction to take place. For the two allyl groups in 6, only the one at Cβ underwent the reaction. In the analogous triethylphosphine complex 6′, more electron-donating triethylphosphine ligands lower the rate of the IMDA reaction. For this IMDA reaction in several vinylidene complexes, each with a nonchlorinated anthracenyl ligand, the rate of the reaction is accelerated by the presence of an unsaturated functional group at Cγ of the vinylidene ligand, particularly by a terminal alkynyl substituent. The solid-state structures of two IMDA reaction products have been determined by single-crystal X-ray diffraction analysis

    Intramolecular Diels−Alder Reactions in Ruthenium Vinylidene Complexes Containing Anthracenyl Groups

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    An intramolecular Diels−Alder (IMDA) reaction was observed at room temperature between an allyl group and a chloroanthracenyl group that were both bonded to the vinylidene ligand of the cationic ruthenium complex [Ru]CC(CH2CHCH2)CH(CH2CHCH2)(C14H8Cl)+ (6; [Ru] = Cp(PPh3)3Ru). The vinylidene ligand functions as a mediator to bring the allyl and the chloroanthracenyl groups in proximity for the reaction to take place. For the two allyl groups in 6, only the one at Cβ underwent the reaction. In the analogous triethylphosphine complex 6′, more electron-donating triethylphosphine ligands lower the rate of the IMDA reaction. For this IMDA reaction in several vinylidene complexes, each with a nonchlorinated anthracenyl ligand, the rate of the reaction is accelerated by the presence of an unsaturated functional group at Cγ of the vinylidene ligand, particularly by a terminal alkynyl substituent. The solid-state structures of two IMDA reaction products have been determined by single-crystal X-ray diffraction analysis

    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

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    Cyclization of the ether enyne <b>1</b> catalyzed by [Ru]­NCCH<sub>3</sub><sup>+</sup> ([Ru] = Cp­(PPh<sub>3</sub>)<sub>2</sub>Ru) in CHCl<sub>3</sub> 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/CHCl<sub>3</sub>, 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]­NCCH<sub>3</sub><sup>+</sup>, 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

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    Cyclization of the ether enyne <b>1</b> catalyzed by [Ru]­NCCH<sub>3</sub><sup>+</sup> ([Ru] = Cp­(PPh<sub>3</sub>)<sub>2</sub>Ru) in CHCl<sub>3</sub> 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/CHCl<sub>3</sub>, 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]­NCCH<sub>3</sub><sup>+</sup>, to give derivatives of tricyclic fluorene, phenanthrene and dibenzo[7]­annulene, respectively, with no intermediate observed
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