Cascade triple-aldehyde addition of 1,2,3,4-tetrakis(pinacolatoboryl)but-2-ene: stereoselective synthesis of 2,3-bis(alkylidene)alkane-1,5-diols.
Treatment of (Z)-1,2,3,4-tetrakis(pinacolatoboryl)but-2-ene, prepared from 2,3-bis(pinacolatoboryl)buta-1,3-diene and bis(pinacolato)diboron, with three molar equivalents of aldehyde in toluene at 100 degrees C gave the 2,3-bis(alkylidene)alkane-1,5-anti-diol as a single stereoisomer. The reaction is applicable to both aromatic and alpha-unbranched aliphatic aldehydes. The 1,5-anti-diols were also synthesized by the one-pot preparation/triple-aldehyde addition of the tetraborylated butene. Experimental results for the stepwise treatment of the butene with two types of aldehydes suggest that the rate-determining step of the triple-aldehyde addition is the third allylation.
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto University Katsura, Nishikyo-ku, Kyoto 615-8510, Japan. shimizu@npc05.kuic.kyoto-u.ac.jp
Masaki
M
Shimizu
Katsuhiro
K
Shimono
Tamejiro
T
Hiyama