Highly Diastereoselective Aldol Reaction of Bicyclo[3.2.1]oct-6-en-3-ones and 8-Oxabicyclo[3.2.1]oct-6-en-3-ones. (E)-Selective conversion into ?-alkylidene ketones
作者:Ingo Stohrer、H. Martin R. Hoffmann
DOI:10.1002/hlca.19930760604
日期:1993.9.22
base-mediated elimination with lithium diisopropylamide/N,N,N′,N′-tetramethylethylenediamine (LDA/TMEDA; Scheme 2). The simple α-methylidene ketones 17a and 18a were obtained via oxidation of the phenylselenides 19 and 20, respectively (Scheme 4). The tertiary aldol 27 was synthesized best by treatment of 1,3-diketone 26 with Me4Zr (Table 4). In this fashion, the facile retro-aldol reaction of 27 was
双环酮1-6与多种醛类进入非对映选择性(> 95%de)醛醇缩合反应(流程1和表1)。通过(i)自发的碱促脱水(方案1和表2),以及(ii)转化成溴甲酸酯和碱介导的消灭,将一系列典型的羟醛选择性地(E)转化为α,β-不饱和酮。二异丙基氨基锂/ N,N,N ',N'-四甲基乙二胺(LDA / TMEDA;方案2)。简单的α-亚甲基酮通过分别氧化苯硒化物19和20获得图17a和18a(方案4)。通过用Me 4 Zr处理1,3-二酮26可以最好地合成叔醇醛27(表4)。以这种方式,有效地抑制了27的容易的逆醛醇缩合反应。