作者:Charles L. Perrin、David B. Young
DOI:10.1021/ja003672y
日期:2001.5.1
To assess stereoelectronic effects in the cleavage of tetrahedral intermediates, a series of five-, six-, and seven-membered cyclic guanidinium salts was synthesized. If stereoelectronic control by antiperiplanar lone pairs is operative, these are expected to hydrolyze with endocyclic C-N cleavage to acyclic ureas. However, hydrolysis in basic media produces mixtures of cyclic and acyclic products
为了评估四面体中间体裂解中的立体电子效应,合成了一系列五元、六元和七元环状胍盐。如果反周面孤对的立体电子控制有效,则预计这些会水解为内环 CN 裂解为无环脲。然而,如 1H NMR 分析所确定,在碱性介质中水解会产生环状和非环状产物的混合物。结果表明,在六元环反周面孤对提供了四面体中间体分解的微弱加速,但在五元环和七元环中没有这种加速的证据,而可以由单对提供这种加速对。