Substitution reactions of sulfolenes

Takayama and colleagues found that cycloreversion can be prevented if the a-carbanion is trapped by formation in the presence of an alkylating agent [116,117]. The solvent and base were also found to be important. Hence, addition of lithium 

John Leonard, Andrew B. Hague and John A. Knight 

Chou and colleagues carried out similar deprotonation/alkylation studies, but using sodium hydride as the base [48]. DMF was found to be the solvent of choice and it was necessary to form the anion in the presence of the alkylating agent to obviate sulfolene ring opening. A mixture of 2-alkyl-3-sulfolenes (74) and the 2-alkyl-2-sulfolenes (75) was usually obtained, as shown by representative 

Using the LiHMDS/in situ alkylating agent conditions for alkylation, the directing effect of different substituents on the double bond of 3-sulfolene was 

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