Cyclization/hydrosilylation of functionalized dienes catalyzed by a cationic palladium phenanthroline complex

Mixtures of(phen)PdMe2 (2a) and HBAr'(4) (3a) or (phen)PdMe(Cl) (2b) and Na BAr'(4) (3b) [phen = 1, 10-phenanthroline; Ar' = 3,5-C6H3(CF3)(2)] catalyze d the cyclization/hydrosilylation of functionalized 1,6-dienes to form sily lated cyclopentanes in good yield and with excellent trans selectivity abou t the newly formed C-C bond (typically >50:1). A range of tertiary hydrosil anes were employed in the procedure although unhindered trialkylsilanes pro vided the most consistent results. The protocol tolerated a range of polar functionality including esters, ethers, amides, sulfones, and cyano groups. 4,4-Disubstitution on the diene backbone promoted cyclization, and a homoa llylic ester, ketone, or ether directing group was required for efficient c yclization. The procedure tolerated dienes which possessed a single trans-s ubstituted olefin and also tolerated allylic substitution. These substitute d dienes underwent cyclization/hydrosilylation to form carbocycles resultin g from transfer of the silyl group to the less hindered olefin. Mixtures of 2a and 3a also catalyzed the cyclization/hydrosilylation of functionalized 1,7-dienes to form silylated cyclohexane derivatives. Cyclization/hydrosil ylation of 1,7-dienes was typically slower, less stereoselective, and more sensitive to substitution than was cyclization of 1,6-dienes.