Novel [1,N]-Carbon to Carbon Rearrangement of an Ester Group via Organotitanium Intermediates Wherein the N Varies from 2 to 5. Full Scope and Limitation Leading Predominantly to the Rearrangement

Article abstract of DOI:10.1246/bcsj.71.1673

Malonates and methanetricarboxylates having an unsaturated side chain such as 2, 12, 20, 22, 24, 31, or 37 underwent a new ester rearrangement reaction promoted by (η²-propene)Ti(O-i-Pr)₂ to afford the succinate derivative 4 or α,β-unsaturated ester 17, 21, 23, 25, 34, or 38 via the migration of the ester group from its original bis- or tris-ester position to the acetylene- or olefin-litanium complex. It has been found that the side reactions competing with the desired migration are dealkylation of the side chain of the ester and a simple cyclization. The substrates and conditions which allow the ester migration a preferential path were determined as well as the scope and limitation of this reaction.