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Herein, we disclose a radical desulfurative C–C coupling protocol for the synthesis of 4-alkylpyridines. A variety of substituents on both benzyl thiols and 4-cyanopyridines are tolerated. The reaction is carried out under mild and photocatalyst- and transition-metal-free conditions. Preliminary mechanistic studies show that an electron donor–acceptor complex is formed between benzyl thiols and 4-cyanopyridines under alkaline conditions. Then, a variety of 1°, 2°, and 3° C(sp3)-centered radicals was formed by cleavage of the C–S bond, and the 4-alkylpyridines were achieved through a radical–radical coupling with the pyridyl radical anion.
Shen et al. (Fri,) studied this question.