Unfunctionalized, α-Epimerizable Nonracemic Ketones and Aldehydes Can Be Accessed by Crystallization-Induced Dynamic Resolution of Imines
作者:Janez Košmrlj、Leland O. Weigel、David A. Evans、C. Wade Downey、Jimmy Wu
DOI:10.1021/ja029715n
日期:2003.3.1
describes an operationally simple deracemization process of aldehydes and ketones. This new crystallization-induced dynamic resolution (CIDR) protocol allows for nearly complete conversion of the racemic mixture into one enantiomer. Crystallization of imines derived from racemic ketones or aldehydes 1 and trans-(1R,2R)-1-amino-6-nitroindan-2-ol (2) afforded diastereomerically pure, crystalline imines 3
Self-Assembly of a Confined Rhodium Catalyst for Asymmetric Hydroformylation of Unfunctionalized Internal Alkenes
作者:Tendai Gadzikwa、Rosalba Bellini、Henk L. Dekker、Joost N. H. Reek
DOI:10.1021/ja211455j
日期:2012.2.15
A chiral supramolecular ligand has been assembled and applied to the rhodium-catalyzed asymmetric hydroformylation of unfunctionalized internalalkenes. Spatial confinement of the metal center within a chiral pocket results in reversed regioselectivity and remarkable enantioselectivities.
Supramolecular Control of Ligand Coordination and Implications in Hydroformylation Reactions
作者:Rosalba Bellini、Samir H. Chikkali、Guillaume Berthon-Gelloz、Joost N. H. Reek
DOI:10.1002/anie.201101653
日期:2011.8.1
The coordination mode of a monodentate phosphoroamidite ligand in a rhodium complex can be switched from equatorial to axial by a unique supramolecular pseudo encapsulation (see scheme). The axial complex has higher activity and selectivity in the challenging asymmetric hydroformylation of internal alkenes.
<i>C</i>-Alkylation of Chiral Tropane- and Homotropane-Derived Enamines
作者:David M. Hodgson、Andrew Charlton、Robert S. Paton、Amber L. Thompson
DOI:10.1021/jo3025972
日期:2013.2.15
The synthesis and alkylation of chiral, nonracemic tropane- and homotropane-derived enamines is examined as an approach to enantioenriched α-alkylatedaldehydes. The two bicyclic N auxiliaries, which differ by a single methylene group, give opposite senses of asymmetric induction on alkylation with EtI and provide modestly enantioenriched 2-ethylhexanal (following hydrolysis of the alkylated iminium)
of 14047 was attained. A mechanistic study indicated that the steric effect of the ethyl group on the α-C of 2-ethylhexanal (2-EHA) and the conjugation effect of C=C–C=O in 2-ethylhex-2-enal (2-EEA) benefits the high selectivity of 2-EH from 1-butanol by inhibiting the cross-aldol reaction of 2-EHA and 2-EEA with butyraldehyde. Nuclearmagneticresonancestudy revealed the formation of a carbonyl group