ChemInform Abstract: Reactions of Endocyclic Linearly Conjugated Dienolates with Michael Acceptors Leading to Bicyclo(2.2.2)octane Derivatives. Application to the Synthesis of C13 Degradation Products of Carotenoids.

Abstract

The endocyclic linearly conjugated dienolates from substituted cyclohex-2-enones react with but-3-en-2-one, substituted methyl propenoates, but-3-yn-2-one and methyl propiolate to afford bicyclo[2.2.2]-oct-2-en-1-ols 10a–c, 14a–c and bicyclo[2.2.2]octa-2,5-dien-1-ols 15a,b. The AlCl3-catalysed reaction of 3,5,5-trimethyl-1-(trimethylsiloxy)cyclohexa-1,3-diene 3 with (E)-4-acetoxy- and (E)-4-methoxy-but-3-en-2-one provides trans-8-acetoxy-7-acetyl-3,5,5-trimethyl-1-(trimethylsiloxy)bicyclo[2.2.2]oct-2-enes 22, 23 and trans-7-acetyl-8-methoxy-3,5,5-trimethyl-1-(trimethylsiloxy)bicyclo[2.2.2]oct-2-enes 24, 25. Starting from these bicyclo[2.2.2]octenes, the C13 degradation products of carotenoids including 3-oxo-α-ionone 20, blumenol-C 27 and 1,3,7,7-tetramethyl-2-oxabicyclo[4.4.0]decan-9-one 29 have been synthesized.