Macrocyclic Ethers by Free Radical Cyclizations

Abstract

Tin hydride reduction of ω-iodo-polyoxaalkyl acrylates 1 using syringe pump addition of both reactants to a solution of AIBN in benzene at 80°C afforded the corresponding cyclic polyethers in excellent yields.

Notes

Some of the cyclised products described herein have been independently prepared from the appropriate iodo precursors by the high dilution technique; Drok, J. K. PhD Thesis, Australian University, Canberra, June 1995 (personal communication).

Indeed, the rate of addition of the reactants cannot be decreased too much since the degradation of the reactants in the needle of the syringe, and then in the syringe, would become the major process (e. g. oligomerization or polymerization of the unsaturated ester).