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8685910 
Journal Article 
Synthesis of 1,9-cis-Diacetoxy-Δ5,10-octalone-6; Stereochemical Course of the Robinson Annelation Reaction 
Spencer, TA; Schmiegel, KK; Williamson, KL 
1963 
Yes 
Journal of the American Chemical Society
ISSN: 0002-7863
EISSN: 1520-5126 
85 
23 
3785-3793 
English 
Michael addition of methyl vinyl ketone to 2-acetoxycyclohexane-1,3-dione (IV) affords an excellent yield of 2-acetoxy-2-(3-oxobutyl)cyclohexane-1,3-dione (XIV), which can be cyclized and dehydrated in a stepwise manner under mild conditions to afford 9-acetoxy-Δ5,10-octalin-1,6-dione (III). The unconjugated ketone group of III can be selectively reduced with sodium borohydride, yielding cis-1-acetoxy-9-hydroxy-Δ5,10-octalone-6 (XL), which results from acetyl migration following reduction. A much better yield of reduced material can be obtained by direct acetylation of the crude sodium borohydride product, which afforded 1,9-cis-diacetoxy-Δ5,10-octalone-6 (XLIII) in about 20% yield from IV. The structures of several by-products resulting from cleavage of β-diketone systems, from aromatization, and from alternate aldol cyclization of XIV to a bridged system have been elucidated. The use of various catalysts for aldol cyclization of XIV has been investigated. The isolation of 9-hydroxy-Δ5,10-octalin-1,6-dione upon acid treatment of the predominant ketol formed in the cyclization implies that this ketol is cis-9-acetoxy-10-hydroxydecalin-1,6-dione (XXX). This marks the first time that it has been possible to deduce the complete stereochemistry of the ketol intermediate which is the direct precursor of the α,β-unsaturated ketones isolated from Robinson annelation reactions. An explanation for the selective formation of the cis-fused XXX is advanced. 1963, American Chemical Society. All rights reserved.