Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations

Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron‐withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition‐metal catalysts were employed. Two possibilities: An indole annulation can be coupled with stereoselective cyclopropanation or dimerization to form complex indole derivatives. The key intermediate is a putative rhodium(I) carbene derived from cycloisomerization of ortho‐aniline‐substituted propargylic alcohols. Boc=tert‐butoxycarbonyl, Ts=4‐toluenesulfonyl.