Utilization of trimethylsilylpropyne as an acetonyl unit in the synthesis of cyclopentenones. Applications to the synthesis of jasmone and dihydrojasmone

The dianion of β-keto esters are alkylated at the γ-carbon with 3-bromo-1-trimethyIsilyl-1-propyne. The resulting alkynes are hydrated (H3O+, Hg2+) and cyclized (OH−) to the corresponding cyclopentenones, jasmone and dihydrojasmone. The failure to obtain cyclopentanones from the acid- and base-catalyzed cyclizations of 6-substituted 3-keto esters may be rationalized by Baldwin's rules for cyclization.