Collect. Czech. Chem. Commun. 2001, 66, 1250-1256

New Cyclodimerization Reaction of (3,5-Di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)acetic Acid

Peter Nesvadbaa,*, Piotr Rzadekb and Günther Ristb

a Ciba Specialty Chemicals Inc., CH-4002 Basel, Switzerland
b Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland


(3,5-Di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)acetic acid 1a underwent on heating a new cyclodimerization reaction affording a 1 : 1 mixture of the racemic cis- and trans-isomeric lactone-acids 2. The decisive structure elucidation of 2 was carried out after its mild esterification with diazomethane and separation of the racemic isomeric methyl esters 3a and 3b. The attempted esterification of 2 with methanol and sulfuric acid gave only the methyl diarylacetate 4. In contrast to 1a, which contains the carboxylic acid functionality no cyclodimerization was observed with the corresponding methyl ester 1b or nitrile 1c.

Keywords: Quinone methides; Cyclodimerization; Diaryl acetates; Butyrolactones; Esterification; Glyoxylic acid; Reaction mechanism.

References: 15 live references.