Synthesis of Nitrogen Heterocycles by Diastereoselective Intramolecular Aminocarbene Annelation

Abstract

Simply heating the carbene complexes 1 in toluene converts them diastereoselectively in 50% yield into the nitrogen-containing tricyclic compounds 2. Whereas the relative configuration of the C atoms with respect to the substituent R and the Cr(CO)3 fragment is established by the metal-induced annelation. the formation of the stereocenter at the point of linkage of the two five-membered rings may be explained by a subsequent, thermodynamically controlled enamine-imine tautomerization step. R = Me, Et, SiMe3.