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-phnylcyclohexyloxy- 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.
图示了三种在C-2位具有手性烷氧基团的二烯烃合成方法。烷氧基
丙烯基膦盐3经过立体选择性的Wittig反应,以高产率得到外消旋或均旋的2-薄荷氧基-、2-(8-苯基薄荷氧基)-、2-反-苯基环己氧基-和2-反-苯基二
甲苯环己氧基丁a-1,3-二烯5a-j(方法A)。由手性醇6衍生的酯通过二甲基
钛茂进行亚甲基化反应,生成手性二烯烃5a、e和7(方法B)。手性α-烷氧基
丙烯醛8通过3的Aza-Wittig反应,接着进行
亚胺水解反应制备,并用于合成多种类型的活化手性烷氧基碳二烯10、12和14(方法C),以及3-烷氧基-1-氮杂
丁二烯衍
生物15。