Rh<sup>III</sup>-Catalyzed [4 + 1] Annulations of 2‑Hydroxy- and 2‑Aminobenzaldehydes with Allenes: A Simple Method toward 3‑Coumaranones and 3-Indolinones
A novel
method for the regio- and stereoselective synthesis of
substituted 3-coumaranones from salicylaldehydes and allenes using
a rhodium(III) catalyst has been developed. This procedure gives access
to new 2-vinyl-substituted 3-coumaranone compounds. The method involves
a Rh<sup>III</sup>-catalyzed aldehyde C–H activation and annulation
reactions. Moreover, this Rh<sup>III</sup>-catalyzed [4 + 1] annulation
reaction has been applied to 2-aminobenzaldehydes to afford 2,2-disubstituted
3-indolinones