Cooperative Catalysis-Enabled (4 + 3) Cycloaddition of 2-Indolylmethanols with Generated -Naphthoquinone Methides.

A cooperative catalysis-enabled (4 + 3) cycloaddition of 2-indolylmethanols with -naphthoquinone methides (-NQMs), which were generated from enynones, has been established in the presence of silver/Brønsted acid cocatalysts. In the reaction pathway, the key -NQM intermediates were formed through Ag(I)-catalyzed cyclization of enynones, while the indole-based carbocation intermediates were generated via Brønsted acid-catalyzed dehydration of 2-indolylmethanols. By this approach, a wide range of seven-membered cyclohepta[]indoles were synthesized in good yields with high efficiency under mild reaction conditions, which serves as a useful strategy toward constructing indole-fused seven-membered rings.

2-tert-Butyl-6-[(4-chloro-2-nitro-phen-yl)diazen-yl]-4-methylphenol.

In the title compound, C(17)H(18)ClN(3)O(3), the dihedral angle between the planes of the two benzene rings is 1.03 (7)°. The overall conformation of the mol-ecule is influenced, in part, by electron delocalization and by an intra-molecular bifurcated O-H⋯(O,N) hydrogen bonds.