title: Rh(I)-catalyzed carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids leading to indenones.
abstract: The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR >> aryl >> alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Harada
authors.forename: Jun
authors.initials: J
authors.lastname: Nakanishi
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Fujihara
authors.forename: Mamoru
authors.initials: M
authors.lastname: Tobisu
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Fukumoto
authors.forename: Naoto
authors.initials: N
authors.lastname: Chatani
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D001897:Boronic Acids / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D007192:Indenes / Q000138:chemical synthesis*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D012238:Rhodium / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: D000480:Alkynes; D001897:Boronic Acids; D007192:Indenes; D014753:Vinyl Compounds; D002248:Carbon Monoxide; D012238:Rhodium