Microwave assisted and in-situ generated palladium nanoparticles catalysed desulfitative synthesis of cross-biphenyls from arylsulfonyl chlorides and phenylboronic acids
Palladium nanoparticles (Pd NPs) are in-situ synthesized under microwave irradiation having diameter of ~ 45 to 55 nm.
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Arylboronic acids and arylsulfonyl chlorides are coupled to produce un-symmetrical biphenyls in high yields.
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Formation of cross-biphenyls was achieved within shorter time along with desulfurization of arylsulfonyl chloride.
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This reaction is an example of In-situ generated Nanoparticles-catalyzed Organic Synthesis Enhancement (i-NOSE) approach.
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Catalyst is easily regenerated and can be reused to get various substituted un-symmetrical biphenyls with good yield.
Abstract
A microwave assisted reaction protocol for Suzuki–Miyaura cross-coupling has been developed. Substituted arylboronic acids and arylsulfonyl chlorides coupled under microwave irradiation (MWI) to produce cross-biphenyls in high yields under aerobic condition. The principal advantage of this protocol is that formation of cross-biphenyls was achieved within shorter time along with desulfurization of arylsulfonyl chloride. In-situ generated Pd nanoparticles (NPs) act as catalyst in the reaction. Substituents like methyl, halogens, cyano, amino and t-butyl groups in arylboronic acids tolerate the reaction condition. Pd NPs could be reused several times under chosen reaction conditions without losing its activity significantly. The product formation and the role of the catalyst for the cross-coupling reaction has been rationalised with the help of a proposed mechanism. This reaction is one of the examples of In-situ generated Nanoparticles-catalyzed Organic Synthesis Enhancement (i-NOSE) approach. The approach derives its importance in terms of catalyst’s (i) simple preparation method, (ii) stability under the chosen reaction condition, (iii) substrate specificity, (iv) simple filtration to recover the catalyst and (v) easy regeneracy which clearly indicate that the approach could be applicable for various types of catalytic transformations.
