A Regioselective Synthesis of Cyclopentenones from 4-Thianone

Article abstract of DOI:10.1021/jo00385a011

Alkyl-substituted 3-cyclopentenones 4 and 5 were prepared in moderate to good yields starting from 4-thianone by the selective alkylation and Ramberg-Baecklund-type reactions.One route starts with 6-alkyl-1,4-dioxa-8-thiaspiro<4,5>decane 8,8-dioxides (8) and another with 7-alkyl-1,4-dioxa-7-(p-tolylsulfonyl)-8-thiaspiro<4,5>decane 8,8-dioxides (15), followed by acid-catalyzed cleavage of the 1,3-dioxolane ring of 1,4-dioxaspiro<4,4>non-7-enes 9 and 16 to afford 4 and 5.