Chiral synthesis VIA organoboranes. 26. An efficient synthesis of isoprenyl derivatives of borane - Valuable reagents for the isoprenylboration of aldehydes. A convenient route to both enantiomers of ipsenol and ipsdienol in high optical purity

Article abstract of DOI:10.1016/S0040-4020(01)85575-7

Preparation of B-isoprenyldialkylboranes is achieved by adopting the Brandsma modification of the Schlosser procedure, namely metallation of isoprene with potassium 2,2,5,5-tetramethylpiperidide followed by sequential treatment with 5-methoxydialkylborane and boron trifluoride-etherate. These reagents are used for the convenient isoprenylation of aldehydes. Reaction of isovaleraldehyde and β, β-dimethylacrolein with B2′isoprenyldiisopinocampheylborane provides both ipsenol and ipsdienol, respectively in 65% yields and 96% ee.