Abstract A simple and effective heterogeneous catalyst based on zeolite-type materials has been developed for the diazo transfer reaction involving 1, 3-dicarbonyl compounds and tosyl azide. α-Diazo carbonyl compounds were obtained under mild conditions in good to high yields using commercial molecular sieve 4A or analogues as the catalyst. The best catalyst was found to be 4A-1000, a synthetic potassium-free nepheline obtained by ...