Excess substrate is a spectator ligand in a rhodium-catalyzed asymmetric [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes.
Excess substrate has been identified as an unintended spectator ligand affecting enantioselectivity in the [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes. Replacement of excess substrate with an exogenous additive affords products with consistent and higher ee's. The increase in enantioselectivity is the result of a change in composition of a proposed rhodium(III) intermediate on the catalytic cycle. The net result is a rational probe of a short-lived rhodium(III) intermediate and gives insight that may have applications in many rhodium-catalyzed reactions.
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Mark Emil
ME
Oinen
Robert T
RT
Yu
Tomislav
T
Rovis
D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D017953:Isocyanates / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009539:Nicotinic Acids / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*
D000475:Alkenes; D017953:Isocyanates; D008024:Ligands; D009539:Nicotinic Acids; C008473:methyl nicotinate; D012238:Rhodium