Module 1 : Reactions using Chiral Lewis Acids and Brønsted Acids

Lecture 1: Reactions Using Chiral Lewis and Brønsted Acids I

1.1.4 β-Lactone Synthesis

Chiral BLA 1c , derived from precatalyst zwitterions and tributyltintriflate, has been investigated for the reaction of aldehydes with ketene to afford β -lactones (Scheme 9).

Examples:

Proposed Mechanism

Reaction of the precatalyst 1c with tri- n -butyltintriflate may give an ion pair that could react with ketene to give sufficiently strong Lewis acid intermediate to make chelation with aldehydes. It is important to note that the formation β -lactone from α -branched aldehydes has been demonstrated for the first time.

Scheme 9