Palladium-catalyzed asymmetric diene cyclization/hydrosilylation employing functionalized silanes and disiloxanes

Pentasubstituted disiloxanes and silanes of the form HSiMe2CHxPh3 (x = 1 or 2) reacted with dimethyl diallylmalonate (1) and other functionalized 1,6-dienes in the presence of a catalytic 1:1 mixture of (N-N)Pd(Me)CI [N-N = (R)-(+)-4-isopropyl-2-(2 pyridinyl)-2-oxazoline] [(R)-2] and NaBAr4 [Ar = 3,5-C6H3(CF3)(2)] to form the corresponding silylated cyclopentanes in good yield with high diastereoselectivity. The enantioselectivity of cyclization/hydrosilylation of 1 with disiloxanes and functionalized silanes at -20 degreesC increased in the following order: HSiMe2OSiMe3 (75% ee) < HSiMe2OSiMe2-t-Bu (80% ee) < HSi(i-Pr)(2)OSiMe3 (86% ee) = HSiMe2Bn (86% ee) < HSiMe2OSi- (i-Pr)3 (89% ee) < HSiMe2OSiPh2-t-Bu (91% ee) < HSiMe2CHPh2 (93% ee). Silylated cyclopentanes. derived from HSiMe2OSiMe3 were oxidized with excess KF and peracetic acid at room temperature for 48 h to form the corresponding hydroxymethyleyelopentanes in good yield (82-95%). Silylated.. cyclopentanes. derived from HSiMe(2)OSiPh(2)t-Bu were oxidized with a mixture of tetrabutylammonium fluoride and either H2O2 Or peracetic acid to form the corresponding alcohols in 48-76% yield. Silylated carbocycles gene rated from benzhydryldimethylsilane were oxidized with a mixture of TBAF/KHCO3/H2O2 in 71-98% yield. Asymmetric cyclization/hydrosilylation/oxidation employing benzhydryldimethylsilane tolerated allylic and terminal olefinic. substitution and a range of functional groups.