The one-pot microwave-assisted synthesis of a series of αylidene δ-lactones from (Z)-2-(bromomethyl)-2-alkenoates (derived from Morita-Baylis-Hillman reaction) in an aqueous environment is reported. The protocol includes regioselective base-mediated allylation of ethyl acetoacetate with (Z)-2-(bromomethyl)-2-alkenoates followed by decarboxylative hydrolysis, carbonyl reduction of the keto carboxylate intermediate, and acid-mediated cyclization of the resulting δ-hydroxy acid to furnish the α-ylidene δ-lactones with good overall yields. The synthesis was also performed in the stepwise mode, which allowed the isolation and full characterization of each intermediate involved in the one-pot method. The main features of this efficient transformation include the fast reaction rates, the use of a benign aqueous medium, the use of inexpensive and readily available reagents, the production of nearly innocuous residues, and the requirement for a single work-up and purification stage at the end of the process.
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