Synthesis of Calix[6]thiophenes and Calix[6]furans

摘要

After thiophene and furan were treated with n-BuLi,respectively,the mixtures were reacted with various ketones and then dehydrated under acidic conditions.This reaction sequence led to the formation of 1-(2-heteroaryl)cycloalkenes and(2-heteroaryl)alkenes.When the alkenes were treated with 10 mol% NIS,calix[4]arenes were produced as the major products,with minor amounts of calix[6]arenes sometimes being produced.Reducing the loading of NIS to 1 mol% and increasing its overall concentration to 6 M resulted in a substantial increase in the yield of hexaspirocyclohexyl calix[6]thiophene(from 2 to 66%).