4,4′-Trimethylenedipiperidine (TMDP): An Efficient Organocatalyst for the Mechanosynthesis of Pyrano[4,3-b]pyrans under Solid-state Conditions
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This paper presents a green protocol for the synthesis of pyrano[4,3-b]pyrans using a catalytic amount of 4,4′-trimethylenedipiperidine (TMDP) as a novel, efficient and recyclable organocatalyst through ball milling process at room temperature. The essential part of this protocol is a Knoevenagel condensation and to the best of our knowledge, this is the first report that exhibits the catalytic efficiency 4,4′-TMDP for the one-pot multicomponent reaction under melt-state conditions. The scope of the present protocol was explored and demonstrated for the synthesis of pyrano[4,3-b]pyrans in an environment-friendly protocol. The several interesting features of the present methodology are including a cost-effectiveness procedure, good to excellent yield of the desired products, high reaction rate, a broad substrate-scope, and recyclability of organocatalyst; as well as the 4,4′-TMDP is a nontoxic, inexpensive, and commercially available catalyst. Furthermore, this efficient methodology displays a combination of the synthetic virtues of conventional multicomponent reaction with ecological benefits and convenience of a facile mechanochemical process.