A ZnI2-catalyzed regioselective cascade 1,4-conjugate addition/5-exo-dig annulation pathway for one-pot access to
Xinwei He1, Pui Ying Choy, Man Pan Leung
1State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The Chinese University of Hong Kong, New Territories, Shatin, Hong Kong SAR, P. R. China. fykwong@cuhk.edu.hk.
Abstract:
Facile access to π-extended heterobiaryl compounds via a non-cross-coupling strategy has been achieved. In the presence of an inexpensive ZnI2 catalyst and versatile propargylamine and β-naphthol (or β-naphthylamine and β-naphthyl mercaptan) starting materials, a variety of sterically hindered heterobiaryl frameworks can be easily obtained. The present catalytic system offers excellent selectivity, good-to-excellent product yields, and good functional group tolerance including, for instance, -CN, -COOH, -C(O)R, -Br and -Cl groups. This cyclization process is proposed to proceed via in situ generated alkynyl o-quinone methides (o-AQMs), following a cascade intermolecular 1,4-conjugate addition/5-exo-dig annulation/1,3-H shift pathway.
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