I. Palladium-catalyzed diene cyclization/hydrosilylation using functionalized silanes. II. Palladium-catalyzed alkylation of unactivated olefins

Reaction of pentamethyldisiloxane with dimethyl diallylmalonate ( 22) catalyzed by a 1:1 mixture of (phen)Pd(Me)Cl (18) [phen = 1,10-phenanthroline] and NaBAr4 (19) [Ar = 3,5-bistrifluoromethylphenyl] (5 mol%) in 1,2-dichloroethane (DCE) at 0°C formed trans-1,1-dimethoxycarbonyl-4-methyl-3-(pentamethyl-disiloxy)methylcyclopentane (23c) in 98% yield with >50:1 diastereoselectivity. Reaction of 22 with pentasubstituted disiloxanes and functionalized silanes catalyzed by a 1:1 mixture of (N-N)Pd(Me)Cl [(R)-21 ] [N-N = (R)-(+)-4-isopropyl-2-(2-pyridinyl)-2-oxazoline] and 19 (5 mol%) in dichloromethane at -20°C formed the corresponding silylated carbocycles in good yield (>90%) with >50:1 diastereoselectivity. The enantioselectivity of cyclization/hydrosilylation of 22 catalyzed by (R)-21/ 19 increased in the order: HSiMe2OSiMe3 (75% ee) < HSiMe2OSiMe2(t-Bu) (80% ee) < HSi(i-Pr)2OSiMe3 = HSiMe 2Bn (86% ee) < HSiMe2OSi(i-Pr)3 (89% ee) < HSiMe2OSiPh2(t-Bu) (91% ee) < HSiMe2CHPh2 (93% ee). The cyclization/hydrosilylation protocol was compatible with a number of functional groups and tolerated allylic and terminal olefinic substitution. Silylated carbocycles derived from pentamethyldisiloxane were oxidized with excess AcOOH and KF at room temperature for 2 days to form the corresponding hydroxymethylcyclopentanes in 82--95% yield. Silylated carbocycles derived from HSiMe2OSiPh2(t-Bu) were oxidized with excess H2O2 or AcOOH and tetrabutylammonium fluoride (TBAF) in 48--76% yield. Silylated carbocycles derived from HSiMe2CHPh2 were oxidized with a mixture of H2 O2/TBAF/KHCO3 in 71--98% yield.; Reaction of 7-octene-2,4-dione (31) catalyzed by PdCl 2(MeCN)2 (10 mol%) in dioxane at room temperature for 16 h led to the isolation of 2-acetylcyclohexanone (32) in 81% yield as a single regioisomer. The Pd(II)-catalyzed cycloisomerization of epsilon-alkenyl beta-diketones tolerated enolic and terminal olefinic substitution to form the corresponding 2-acylcyclohexanones as single regioisomers in 61--89% yield. Reaction of 8-nonene-2,4-dione (52) with PdCl2(MeCN)2 (5 mol%) and CuCl2 (3 equiv) in DCE at room temperature for 2 h formed 2-acetyl-3-methyl-2-cyclohexenone (53) in 80% yield. Reaction of methyl 6-heptenoate (59) with PdCl2(MeCN) 2 (10 mol%) and ClSiMe3 (2 equiv) in dioxane at room temperature for 8 h formed 2-methoxycarbonylcyclohexanone (60) in 91% yield. (Abstract shortened by UMI.)...