3-Arylidene-4-Chromanones and 3-Arylidene-4-Thiochromanones: Versatile Synthons towards the Synthesis of Complex Heterocycles

Heterocyclic compounds are well-known for their use in the synthesis of drugs and drug intermediates. This review provides a systematic survey on the chemical synthesis of complex heterocyclic compounds containing multi-stereocentres using 3-arylidene-4-chromanones in the last two decades. Regioselective and stereoselective synthesis of complex heterocycles involving 3-arylidene-chromanones and 3-arylidene-thiochormanones are dealt under various reaction headings such as epoxidation, Michael addition, 1,3-dipolar cycloaddition, [3+2] and [4+2] cycloaddition, Diels-Alder reaction, sulfa-Michael/aldol cascade reactions, asymmetric synthesis employing bifunctional catalysts, chiral phase-transfer catalysts, chiral squaramide catalysts, etc. These synthetic highlights demonstrate the utility of 3-arylidene-4-chromanones and 3-arylidene-thiochormanones as versatile synthons for rapid assemblage of complex condensed heterocyles and spiro-fused heterocycles towards the development of pharmaceutically active compounds. A brief highlight on the synthetic methods of 3-arylidene-4-chromanone derivatives is also dealt. This review creates a platform for further improvement on the skeletal design of potential drug candidates.