Substituent-Controlled Regiodivergent Rearrangement of Gramine Ammonium Ylide.

The complicated mechanism makes the regiodivergent rearrangement of ammonium ylide seem to be out of reach. Herein, we reported a regiodivergent rearrangement of gramine ammonium ylide well controlled by the substituents. Density functional theory studies reveal that the ammonium ylide with a more steric hindrance substituent 2-diazo-2-arylacetate goes through a stepwise mechanism to yield both a kinetically and thermodynamically preferred [1,2]-rearrangement product.

Synthesis of Azepino[4,5-]indole via Ring Expansion of Tetrahydro-β-carbolines Ammonium Ylide.

The formal cyclization strategy was generally used to construct azepino[4,5-]indole. Herein, we reported a novel and expeditious protocol for the synthesis of quaternary carbon azepino[4,5-]indole via ring expansion of ammonium ylide, which was formed by the reaction of tetrahydro-β-carbolines with the diazo compound. The easily available substrates, mild reaction conditions, and broad functional tolerance rendered this method a practical strategy that may significantly afford an efficient method of scaffold hopping in drug discovery.