Diastereoselective intermolecular rhodium-catalyzed [4 + 2 + 2] carbocyclization reactions: computational and experimental evidence for the intermediacy of an alternative metallacycle intermediate.
Intermolecular rhodium-catalyzed [m + n + o] reactions of 1,6-enynes and various pi-components (carbon monoxide, alkynes, 1,3-butadienes, etc.) provide an expeditious approach for the construction of polycyclic fragments that represent important synthons for target-directed synthesis. We present computational and experimental evidence for the existence of a previously undescribed reaction pathway for the rhodium-catalyzed [4 + 2 + 2] reaction involving a 1,6-enyne. This model clearly demonstrates the origin of the excellent diastereoselectivity in this type of reaction and the remarkable tolerance of both (E)- and (Z)-isomers within the 1,6-enyne, which is generally prone to competitive ene-cycloisomerization.
Baik
Mu-Hyun
MH
Department of Chemistry and School of Informatics, Indiana University, Bloomington, IN 47405, USA. mbaik@indiana.edu
Baum
Erich W
EW
Burland
Matthew C
MC
Evans
P Andrew
PA