Vinyl carbinols, isomerization

The cleanest product composition may be effected by decomposition of the pure hydroperoxide or solutions in the injection block of the gas chromatograph. In carbon tetrachloride solution only methyl vinyl ketone and methyl vinyl carbinol were produced, the ratio of ketone to alcohol being 2.9. No definite traces of products from isomerized hydroperoxide were observed. 

The work of Nazarov on vinyl ethynyl carbinols involves condensation of vinylacetylene with ketones in the presence of caustic potash and also their conversions, many of which are catalytic in nature. A review of his work involving polymerization, isomerization, hydrogenation, and other conversions was published by him (252). Hydration of divinylacetylenes in methanol solution in the presence of mercuric sulfate and sulfuric acid gave vinyl alkyl ketones. These can be reacted with hydrogen sulfide, amines, etc., to yield heterocyclic compounds. Substituted vinyl alkyl ketones underwent spontaneous cyclization to cyclopentenones. Nazarov summarized a decade of this research in this field in 1951 (253). His general review of organic syntheses based on acetylene is also of interest in this connection (254). 

Other variations of the 3,3-rearrangement have been reported where the vinyl unit is incorporated into a ring. Addition of vinyllithium to a cyclohexanespirocyclobutanone produces a mixture of two stereo-isomeric alkoxides, one of which on warming to room temperature undergoes a smooth anionic oxy-Cope rearrangement to the octahydrobenzocyclooctene, while the other suffers ring fission (Scheme 55). Interestingly, if the carbinols are isolated fu-st by a low temperature quench and then transformed... 

Zard has studied the isomerization/Mislow-Evans rearrangement of vinyl sulfoxides such as 237, arising from enolate addition to alkynyl sulfoxides [Scheme 18.60). Isomerization of 237 to the allylic sulfoxide 238 enabled the [2,3]-sigmatropic rearrangement to a-hydroxy-a-vinyl ketone 239. In this case, diastereoselectivity was low in formation of the carbinol center within a steroid framework. Additions to allenyl sulfoxides provide a similar sequence, leading to 2-propenyl substitution at the tertiary alcohol center (not shown). 

Combined with the efficient and regiospecific alkylation of allylic sulphones shown in the Scheme (contrast the corresponding alkylation of allylic sulphox-ides), this method can give allylic alcohols trisubstituted on the carbon-carbon double bond. The sequence can also be adapted to open up two new routes to exocyclic a-methylene-carbinols (32) (Scheme 15)/" either by overall [1,3] transposition of oxygen from (33), or from ketones via the vinyl sulphones (34), which are isomerized to the thermodynamically favoured allylic isomers (35). 

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