Dipolar Cycloaddition Reactions of Dihydropyrimidine-Fused Mesomeric Betaines. An Approach toward Conformationally Restricted Dihydropyrimidine Derivatives<sup>1</sup>
作者:C. Oliver Kappe、Karl Peters、Eva-Maria Peters
DOI:10.1021/jo970121q
日期:1997.5.1
mesomeric thiazinium betaines underwent 1,4-dipolar cycloaddition reaction with electron-rich dipolarophiles such as ynamines or ketene acetals. In general, these cycloadditions show a high degree of regioselectivity, facial selectivity, and exo/endo diastereoselectivity. Intramolecular variations of the above processes involving o-alkenylaryl-tethered dihydropyrimidine-fused isomünchnones lead to
研究了各种4-芳基二氢嘧啶融合的介观甜菜碱的双分子和分子内环加成潜力。发现与二氢嘧啶稠合的异硫氰酸盐和异硫氰酸盐与缺电子的双极性亲和剂如DMAD,丙酸甲酯,甲基乙烯基酮或N-甲基马来酰亚胺发生1,3-偶极环加成反应。相反,交叉共轭的中观硫代噻唑鎓甜菜碱与富含电子的亲电性亲电子试剂如乙胺或乙烯酮缩醛进行1,4-偶极环加成反应。通常,这些环加成物表现出高度的区域选择性,面部选择性和外/内非对映选择性。涉及邻链烯基芳基拴系的二氢嘧啶稠合的异麦草酮的上述过程的分子内变化导致多环二氢嘧啶类似物,其类似物模仿拟议的二氢吡啶钙通道调节剂的受体结合构象。这些环加合物是π键向加在异麦草酮系统中的羰基内酯偶极内加的结果。这些环加合物的相对立体化学是通过单晶X射线分析确定的。