Dipolar cyclopentene formation

Nucleophilic participation of HMPT has been reported in dipolar aprotic solvents. Formation of a sulfonium salt has been observed in an acid-catalyzed reaction in DMSO. Another research group has examined the nucleophilic splitting of stereoisomeric 3-methoxycyclopentene and hexene oxides. Detailed studies have been performed on the geometry of the transition state in the reactions of cyclopentene and cyclohexene oxides, and their competitive opening by charged and neutral nucleophiles in acidic aqueous methanol. Other authors have dealt with the opening of epoxynorbornenes and the nature of the inter-... 

The first synthesis of this compound to be completed was the result of studies by Smith and co-workers in 1982. The readily available flavor constituent cyclotene (368) (Scheme 2.28) was reduced and isomerized to 2-methyl-2-cyclopenten-l-one (369) in 64% yield. Addition of dimethyl cuprate followed by isomerization and Baeyer-Villiger oxidation gave the racemic 8-lactone 370 (86%). Addition of allyl Grignard reagent followed by formation of the methyl ketal provided a 71% yield of 371, which possesses the expected axial methoxy group. Conversion of the terminal olefin into the functionalized isoxazoline 373 was accomplished in 68% by the 1,3 dipolar cycloaddition of nitrile oxide 372. 

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