Rapid alcoholysis of cyclic esters using metal alkoxides: access to linear lactyllactate-grafted polyglycidol

Abstract

A facile alcoholysis of L-lactide (LA) and lactones was developed using inexpensive and commercially available Al(OⁱPr)₃ (1), Ti(OⁱPr)₄ (2), and Zr(OⁱPr)₄.ⁱPrOH (3) yielding alkyl (S,S)-lactyllactates and hydroxy esters. Complex 1 was the most efficient for the methanolysis of LA at 70 °C finishing very rapidly within 10 min selectively giving 99% methyl (S,S)-lactyllactate. The alcoholysis can be extended efficiently to other functional alcohols containing triple bonds, and methacrylate, and epoxide groups. The alcoholysis of LA by 1 with glycidol gave glycidyl (S,S)-lactyllactate as a new epoxide monomer in excellent yield. This monomer can be polymerized selectively at the epoxide group by 1 giving a novel linear polyglycidol having precisely one biodegradable lactyllactate unit grafted on each glycidol molecule that has not been accessible by previous methods.