title: Palladium-catalyzed silylene-1,3-diene [4 + 1] cycloaddition with use of (aminosilyl)boronic esters as synthetic equivalents of silylene.
abstract: Silylboronic esters bearing a dialkylamino group on the silicon atoms reacted with 1,3-dienes in the presence of a palladium catalyst to give silacyclopent-3-enes (i.e., 2,5-dihydrosiloles) in high yields via efficient silylene transfer from the silylboronic ester to the 1,3-dienes. The [4 + 1] cycloaddition was applicable to the parent 1,3-butadiene and various mono-, di-, and trisubstituted 1,3-dienes having silyloxy, cyano, and ester groups. Stereospecific ring formation took place in the reaction with either stereoisomer of 5,7-dodecadiene: the (E,E)-diene gave the cis product, whereas selective formation of the trans product was observed in the reaction of the isomeric (E,Z)-diene. The [4 + 1] cycloaddition followed by dehydrogenation with DDQ or chloranil afforded 2,4- and 2,5-diarylsiloles.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto 615-8510, Japan.
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Ohmura
authors.forename: Kohei
authors.initials: K
authors.lastname: Masuda
authors.forename: Ichiro
authors.initials: I
authors.lastname: Takase
authors.forename: Michinori
authors.initials: M
authors.lastname: Suginome