Divergent Reactions between [alpha]-Imino Rhodium Carbenoids and 1,3-Diketones: Substrate-Controlled O-H versus C-H Insertion

The cyclization reaction between N-sulfonyl-1,2,3-triazoles and 1,3-diketones was explored. This reaction provides a new and powerful method for the synthesis of highly functionalized pyrroles and fused pyrrole derivatives. Mechanistically, the reaction was found to proceed through tandem O-H or C-H insertion/condensation of in situ generated [alpha]-imino rhodium carbenoids with 1,3-diketones. The initial O-H or C-H insertion was determined to be dependent on the type of 1,3-diketone.