American Chemical Society
om200859z_si_002.cif (75.28 kB)

Enantioselective Catalysts for the Diels–Alder Reaction between Methacrolein and Cyclopentadiene Based on the Chiral Fragment (η5-C5Me5)M(chiral diphosphane) (M = Rh, Ir)

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posted on 2011-12-26, 00:00 authored by Daniel Carmona, Fernando Viguri, Ainara Asenjo, M. Pilar Lamata, Fernando Lahoz, Pilar Garcı́a-Orduña, L. A. Oro
The aqua complexes [(η5-C5Me5)­M­(PP*)­(H2O)]­[SbF6]2 (M = Rh, Ir; PP* = chiral diphosphane) (110) are prepared and characterized. These complexes efficiently catalyze the Diels–Alder reaction between methacrolein and HCp with enantioselectivities of up to 96% e.e. The norphos complexes 9 and 10, which are obtained as diastereomeric mixtures of the two epimers at the metal, afford the highest e.e. values. The intermediate complexes [(η5-C5Me5)­M­(PP*)­(methacrolein)]­[SbF6]2 (1120) are also isolated and characterized, including the molecular structure determination of the [(η5-C5Me5)­M­(benphos)­(methacrolein)]­[SbF6]2 (M = Rh (13), Ir (14)) derivatives. An NMR study of the reactivity of the metallic intermediates under catalytic conditions explains the high enantioselectivities achieved with the norphos systems.