A facile tandem approach has been established for the convenient diastereoselective synthesis of novel pyrazole and α-methylene-γ-butyrolactone based molecular hybrids. Indium-mediated Barbier-type allylation reaction was performed followed by in situ lactonisation approach. No additive was needed for this transformation and the butyrolactone derivatives were obtained with syn stereochemistry in good yields. The current protocol offers several advantages such as one-pot procedure, high diastereoselectivity, broad substrate scope and good yields of the desired products.