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Excess substrate is a spectator ligand in a rhodium-catalyzed asymmetric [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes.

ABSTRACT: 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.

SUBMITTER: Oinen ME

PROVIDER: S-EPMC2777613 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Excess substrate is a spectator ligand in a rhodium-catalyzed asymmetric [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes.

Oinen Mark Emil ME Yu Robert T RT Rovis Tomislav T

Organic letters 20091101 21

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 ...[more]

PMID: 19803471

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