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Abstract
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We report a novel and environmentally benign multicomponent reaction (MCR) strategy for the synthesis of
C-4 sulfenylated pyrazoles promoted by Na2S2O3$5H2O. This metal-free, one-pot protocol enables the
simultaneous formation of two C–N bonds and one C–S bond through a cascade of cyclocondensation
and direct C–H sulfenylation. A wide range of aryl and alkyl hydrazines and disulfides are efficiently
converted to the corresponding products in good to excellent yields (72–94%) under sustainable
conditions. DMSO plays a dual role as both the reaction medium and a modulator facilitating thiyl radical
generation, which is essential for achieving regioselective C-4 sulfenylation. Compared to previously
reported metal-catalyzed methods, this protocol offers high atom economy, broad substrate scope, and
reduced environmental footprint, aligning well with the principles of green chemistry and advancing
sustainable synthetic methodologies in heterocyclic chemistry.
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