Reactions of Polycyclic Ketones with Dimethoxycarbene; a Convenient Route for a ‘One‐Pot’ Preparation of Some α‐Hydroxycarboxylic Acid Esters

Abstract

Polycyclic cage ketones, such as pentacyclo [5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecan-8-one (10), pentacyclo[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane-8,11-dione (11), and adamantan-2-one (16) were treated with the nucleophilic dimethoxycarbene (DMC; 1), which was generated thermally from 2,5-dihydro-2,2-dimethoxy-5,5-dimethyl-1,3,4-oxadiazole (4a) in boiling toluene. In this one-pot procedure, the ahydroxycarboxylic acid ester 12 or a corresponding derivative 15 or 17 was obtained (Schemes 4 -7). Additionally, cage thione 21 was treated with DMC under the same conditions yielding dimethoxythiirane 22 (Scheme 8). Subsequent hydrolysis or desulfurization (followed by hydrolysis on silica gel) of 22 gave a-mercaptocarboxylate 25 and the corresponding desulfurized ester 24, respectively. In all cases, the addition of DMC occurred stereoselectively, and the addition from the exo-face is postulated to explain the structures of the isolated products.

Carbenes and Nitrenes

“…The same group reported the addition of DMC to polycyclic ketones as an efficient route to polycyclic α-hydroxy esters. 100 DMC also proved to be an alkoxyacyl anion equivalent in the reaction with polycyclic thiones, but the reaction required acidic hydrolysis to go to completion. Reaction of an excess of DMC with dimethyl 2,3-dicyanomaleate at 50 • C afforded a mixture of cyclobutane (63) and dihydrofuran (64).…”