ChemInform Abstract: Structure and Temperature Effects on the Cyclization of Rigid Bisacetylenes.

Abstract

ring closure reactions ring closure reactions O 0130 -051Structure and Temperature Effects on the Cyclization of Rigid Bisacetylenes.-Cyclodimerization of acetylenic compounds (I), using CuCl/CuCl 2 in pyridine as catalyst/oxidant mixture, depends on the arrangement of the functional groups (suggesting that the copper salts act as template) and strongly on the temperature. Due to the aliphatic spacer, the acyclic dimeric intermediate of (Ib) has the highest mobility and, thus, the highest probability to react intramolecularly. The optimum reaction temperature is around 60 • C for optimum yields between 50 and 70%. The cyclic trimer of acetylenic compound (II) is formed in about 35% yield regardless of whether the reaction takes place at room temperature or 65