Rhodium-Catalyzed Tandem C–H Annulation Enabled by Transient Directing Group Strategy and Sequential Nucleophilic Substitution

Abstract

A novel protocol of rhodium-catalyzed tandem C–H annulation of aldehyde and aniline with diazonaphthalen-1(2H)-one via transient directing group strategy and sequential nucleophilic substitution has been demonstrated in moderate to excellent yields. This reaction proceeds smoothly via intramolecular cyclization to form 6H-benzo[c]chromen-6-ol and is followed by nucleophilic substitution of para-carbon of aniline to construct 6-aryl-6H-benzo[c]chromene derivatives. A series of 6-aryl-6H-benzo[c]chromenes were synthesized in one-pot via the tandem C–H annulation.

Diazo Quinone: An Effective Phenolic Precursor for Building C(sp2)−C(sp2) Bonds

“…Transient directing group (TDG)-imines, were in situ generated from aldehyde and aniline and then coordinated with Cp*Rh-catalyst to promote the C(sp 2 )À H bond activation. [70]…”

“…Subsequent sequential nucleophilic substitution gave 6‐aryl‐6H‐benzo[c]chromene derivatives ( 120 – 122 ) in moderate to excellent yields (Scheme 20). Transient directing group (TDG)‐imines, were in situ generated from aldehyde and aniline and then coordinated with Cp*Rh‐catalyst to promote the C(sp 2 )−H bond activation [70] …”