Efficient approaches to the stereoselective synthesis of chiral 2-alkoxydienes and heterodienes

Article abstract of DOI:10.1055/s-1997-1294

Three approaches to dienes having a chiral alkoxy group at C-2 are shown. Alkoxypropenylphosphonium salts 3 undergo stereoselective Wittig reaction affording high yields of racemic and/or homochiral 2-menthyloxy-, 2-(8-phenylmenthyloxy)-, 2-trans-phenylcyclohexyloxy- and 2-trans-mesitylcyclohexyloxybuta-1,3-dienes 5a-j (Method A). Esters derived from chiral alcohols 6 are methylenated with dimethyltitanocene to yield chiral dienes 5a,e,7 (Method B). Chiral α-alkoxyacroleins 8 are prepared by the aza-Wittig reaction of 3 followed by imine hydrolysis and utilized for synthesizing various types of activated chiral alkoxycarbodienes 10,12 and 14 (Method C), as well as 3-alkoxy-1-azabutadiene derivatives 15.