B-2′-isoprenyldiisopinocampheylborane: An efficient reagent for the chiral isoprenylation of aldehydes. A convenient route to both enantiomers of ipsenol and ipsdienol
Isoprene has been metalated in tetrahydrofuran with an excess of sterically hindered potassium dialkylamides, prepared by combining equimolar amounts of the corresponding lithium amide and potassium tert-butoxide. Subsequent reaction with oxirane, alkyl bromides, and pivaldehyde gave the expected coupling products in reasonable yields. Coupling with (CH3)2CHCH2CHO and (CH3)2CCHCHO afforded the bark