Add time:09/06/2019         Source:sciencedirect.com

In this paper, a Rh(III)-catalyzed cascade reaction of benzoyl acetonitriles/methylsulfones (1) with cyclic 2-diazo-1,3-dicarbonyl compounds (2) leading to a convenient and efficient preparation of diversely functionalized naphtho[1,8-bc]pyrans is presented. Mechanistically, the formation of the title compounds involves a cascade process including: 1) C(sp2)H/C(sp3)H bonds cleavage, metalation and carbeniod insertion of 1 with 2 followed by an intramolecular annulation to afford substituted 1-naphthol as a key intermediate; 2) C(sp2)H/OH bonds cleavage, metalation and carbeniod insertion of the in situ formed 1-naphthol intermediate with 2 followed by an intramolecular cyclization to give the naphtho[1,8-bc]pyran product. Compared with literature methods for the synthesis of naphtho[1,8-bc]pyran derivatives, this new protocol has advantages such as simple operational procedure, easily obtainable substrates, high efficiency and excellent atom-economy.

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