A rapid, efficient, and solvent-free methodology for synthesis of exocyclic α , β -unsaturated ketones of the categories E -3-arylidene-4-chromanones, E -2-arylidene-1-tetralones, E -2-arylidene-1-indanones, E -3-cinnamylidene-4-chromanones, E -2-cinnamylidene-1-tetralones, E -2-cinnamylidene-1-indanones, α , α ′-( E,E )-bis(arylidene)-cycloalkanones, and α , α ′-( E,E )-bis(cinnamylidene)-cycloalkanones has been developed through cross-aldol condensation of the constituent cyclic ketones and aldehydes by microwave irradiation over anhydrous potassium carbonate. However, for condensation of 1-thio-4-chromanones with aromatic aldehydes by this method, the initially formed exocyclic α , β -unsaturated ketone has been found to undergo isomerization yielding 3-(arylmethyl)thiochromones.
Mondal, R., Mandal, T. K., & Mallik, A. K. (2012). An Expeditious and Safe Synthesis of Some Exocyclic α , β -Unsaturated Ketones by Microwave-Assisted Condensation of Cyclic Ketones with Aromatic Aldehydes over Anhydrous Potassium Carbonate . Organic Chemistry International, 2012, 1–8. https://doi.org/10.1155/2012/456097