Abstract
Eleven new tetrahydrobenzo[b]pyran derivatives were synthesized via a three component reaction of different aromatic aldehydes, methyl cyanoacetate and 1,3-cyclohexadione, with water as solvent under catalyst-free microwave irradiation. The structures of all the new molecules were well analysed and their structures established by using various spectral techniques (1H NMR, 13C NMR, 15N NMR and HRMS). Various advantages of reported protocol are the ease of preparation, short reaction times (10 min), aqueous solvent and excellent yields (89–98%). Additionally, this method provides a clean access to the desired products by simple workup.
Highlights
Multi component reaction (MCR) is an important technique for the effective and swift synthesis of a wide range of composite heterocyclic frameworks [1,2,3]
Reaction optimization Based on preliminary studies, 2-methoxy benzaldehyde (1 mmol), methyl cyanoacetate (1.1 mmol) and 1,3-cyclohexadione (1 mmol) were identified as ideal for the multicomponent reaction
The effect of solvent on the reaction were assessed under microwave irradiation (MWI) and conventional heating conditions
Summary
Multi component reaction (MCR) is an important technique for the effective and swift synthesis of a wide range of composite heterocyclic frameworks [1,2,3]. MCR is a distinctly focused approach for organic synthesis, because of their ability to make composite molecular functionality from the three or more starting materials through one-pot reaction [3,4,5] and for the creation of new C–C and C–O bonds [6]. Reactions facilitated by microwave irradiation (MWI) have attracted significant attention, owing to the environmental benign operational simplicity and higher selectivity [8, 9]. With advent of MWI, catalyst-free and solvent-free reactions have increased as they provide an opportunity to work with open vessels [12]. It circumvents the problems associated with higher-pressure conditions and offers a possibility for scaling-up the reaction under a moisture free environment [13]. MWI offers other benefits including reduced reaction time, fast reaction optimization, mild reaction conditions, higher yields, reproducibility, lower solvent consumption and ease of synthesis of difficult compounds [14]
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