A study on the influence of steric and electronic effects of a function attached at C-2 of furans in the yield and diastereoselectivity of [4+3] cycloaddition reactions with oxyallyl cations is presented. In almost all studied furans a cis diastereospecificity and a high endo diastereoselectivity is observed. Increasing bulkyness of the function attached at C-2 of furans, increases the endo diastereoselectivity, but decreases yield. Increasing the electronic density of the furan system, by an electron donating group attached at C-2, increases yield and diastereoselectivity.
本文研究了
呋喃的 C-2 上所附函数的立体效应和电子效应对与氧烯丙基阳离子发生 [4+3] 环加成反应的产率和非对映选择性的影响。在几乎所有研究的
呋喃中,都观察到了顺式非对映专一性和高度非对映选择性。增加
呋喃 C-2 上所附官能团的体积可提高内向非对映选择性,但会降低产率。通过在 C-2 上连接一个电子供体来增加
呋喃体系的电子密度,可以提高产率和非对映选择性。