Acetoxymercuration vinylallenes

Typical yields are in the range of40-70% regardless of the method used. We should mention that the acetoxymercuration and acetoxythallation of vinylallenes also lead to cyclopentenones, albeit not via epoxide formation [28]. 

A similar electrophilic activation of the vinylallene to 2-cyclopentenone cyclization is possible using either mercury(II) acetate or thallium acetate. Solvometallation of allenes is a well studied pro-cess following expected Markovnikov attack at the central carbon by the metal salt. The yield of cyclopentenones was generally higher with acetoxymercuration (49-79%) compared to acetoxythallation (25-68%). Compounds of similar substitution pattern as were investigated with epoxidation (Scheme 31) were prepared. Mechanistically the reaction is remarkable for the facility of solvodemercuration (Scheme 33). Intermediates such as (69) or (70) lose elemental mercury spontaneously in the acetic acid medium to give the 2-cyclopentenones. 

Acetoxymercuration. Cyclopentenones (2) can be obtained by acetoxy-mercuration of vinylallenes (1). This route is an extension of the cyclization method of Julia (5, 426-427). 

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