Synthesis of Biaryls and Oligoarenes Using Aryl[2-(hydroxymethyl)phenyl]dimethylsilanes
作者:Jinshui Chen、Masaaki Tanaka、Akhila K. Sahoo、Masahide Takeda、Akira Yada、Yoshiaki Nakao、Tamejiro Hiyama
DOI:10.1246/bcsj.20090325
日期:2010.5.15
Through intramolecular activation, highly stable aryl[2-(hydroxymethyl)phenyl]dimethylsilanes can selectively transfer their aryl groups to effect a cross-coupling reaction with various aryl bromides and chlorides in the presence of a weak non-fluoride base and a palladium/copper catalyst. This reaction tolerates a wide range of functional groups, producing the corresponding functionalized biaryls in high yields with excellent chemoselectivity. Newly disclosed reaction conditions allow the recovery of a cyclic silyl ether in modest-to-good yields and reuse for the synthesis of the arylsilanes. The introduction of two isopropyl groups on the silicon center instead of methyl groups improves the stability and allows quantitative recovery of the silicon residue. Finally, aryl halides having an O-protected [2-(hydroxymethyl)phenyl]dimethylsilyl group cross-couple with the arylsilane reagents to give silyl-functionalized biaryls. Upon deprotection, the biaryls further react with the silylated electrophiles. The iterative cross-coupling–deprotection sequences allow rapid assembly of silylated oligoarenes. Syntheses of di- and trisilyloligoarenes are also achieved by use of orthogonal O-protecting groups.
Let's coordinate: Copper(I)‐catalyzed cross‐coupling of alkenyl‐ and arylsilanes with primary alkyl iodides as well as allylic and benzylic halides as C(sp3)X electrophilic coupling partners has been realized by intramolecular activation through alkoxide coordination. This alkylation tolerates a range of functional groups including a free hydroxy group. IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene
achievement of the corresponding enantioselective transformations using the tetraorganosilicon reagents, providing the silicon-based approach to opticallyactiveketones and substituted piperidones that serve as synthetic intermediates of pharmaceuticals. A rhodium alkoxide species is suggested to be responsible for a transmetalation step on the basis of the observed kinetic resolution of a racemic chiral phenylsilane