Condition based divergence in synthesis of tetrahydrobenzo[b]pyrans

An environmentally benign novel strategy is developed for the synthesis of tetrahydrobenzo[b]pyrans by using thiamine mononitrate as a green catalyst, with the help of a conventional as well as non-conventional energy source. Synthesis of tetrahydrobenzo[b]pyrans is achieved by one pot condensation of aromatic aldehydes, malononitrile and dimedone in a water-ethanol system. Use of aqueous reaction media, mild conditions, water stable catalyst and energy plummeting process as well as excellent yield, are the key features in completing the reaction. This method excludes the use of volatile organic solvents, tedious workup and column chromatographic purification of compounds, making the method greener, convenient and superior. [GRAPHICS] .