Enantioselective synthesis of 2-substituted-1,4-diketones from (S)-mandelic acid enolate and α,β-enones
作者:Gonzalo Blay、Isabel Fernández、Belen Monje、M. Carmen Muñoz、José R. Pedro、Carlos Vila
DOI:10.1016/j.tet.2006.07.036
日期:2006.9
diastereoselectivities. The addition of HMPA (3 equiv) reverses and strongly enhances the diastereoselectivity of the reaction. A change in the reaction mechanism from a lithium catalyzed to the one where catalysis has been suppressed by coordination of HMPA to lithium is proposed to explain these results. Subsequent basic hydrolysis of the 1,3-dioxolan-4-one moiety yields the corresponding α-hydroxy acids (in
已经开发了一种由(S)-扁桃酸和α,β-烯酮合成手性非外消旋2-取代-1,4-二酮的方法。旋光(S)衍生的1,3-二氧戊环4-1的烯酸锂的反应。-扁桃酸和新戊醛与α,β-不饱和羰基化合物的反应容易进行,从而以高收率和高非对映选择性产生相应的迈克尔加合物。HMPA(3当量)的添加会逆转并大大提高反应的非对映选择性。为了解释这些结果,提出了将反应机理从催化的锂改变为通过HMPA与锂的配位而抑制了催化的反应的改变。1,3-二氧杂戊环-4-酮部分的随后碱性水解产生相应的α-羟基酸(半缩醛形式),在新戊醛和Co(III)Me 2 opba络合物作为催化剂存在下与氧脱羧后得到具有非常高对映体过量的手性2-取代的1,4-二羰基化合物。在这种方法中,(S)-扁桃酸起苯甲酰基阴离子的手性手性当量的作用。