Cycloadditions. Part II. A steric effect in the 1,3-dipolar addition of 2-diazopropane to methyl but-2-ynoate
作者:A. C. Day、R. N. Inwood
DOI:10.1039/j39690001065
日期:——
5-methoxycarbonyl-3,3,4-trimethyl-3H-pyrazole being obtained in the ratio 6 : 1. In contrast, methyl propiolate behaves normally with 2-diazopropane, giving solely 3,3-dimethyl-5-methoxycarbonyl-3H-pyrazole. The preference for reverse addition to methyl but-2-ynoate is attributed to steric factors in the transition states for cycloaddition.
将1-二偶氮丙烷在丁-2-酸甲酯中的1,3-偶极加成反应的主要模式与以电子学理由预测的相反,即4-甲氧基羰基-3,3,5-三甲基-3 H-吡唑和5-甲氧基羰基-3,3,4-三甲基-3- ħ吡唑在比6而获得:1.在相反,丙炔酸甲酯的行为通常与2-重氮丙烷,得到仅3,3-二甲基-5-甲氧基羰基-3- ħ -吡唑。反向添加到丁酸2-丁酸甲酯的偏爱归因于环加成过渡态中的空间因素。