Dialkylation of Ethyl 4-(Het)aryl-3-oxobutanoates as a Route to 5-(2-Oxoethyl)cyclopentenones

Abstract

An unexplored ability of the long-known chemical transformation, Borsche’s cyclopentenone synthesis (the construction of a 1,4-diketone with subsequent base-induced cyclization), is reported. Double alkylation of ethyl 4-(het)aryl-3-oxobutanoates with 2-bromo-1-(het)arylethanones, with subsequent alkali treatment, provides access to cyclopentenones substituted with a 2-oxoethyl group at the 5-position. These products might serve as valuable synthons for heterocyclization, and this feature was demonstrated by synthesis of 4H-cyclopenta[b]thiophene derivatives.

Key words

cyclopentenones - cyclization - heterocyclization - diketones - Borsche’s synthesis - cyclopentathiophene

• References and Notes

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• 15 CCDC 1904288 contains the supplementary crystallographic data for compound 9. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/getstructures.