Catalytic and Structural Studies on Complexes of a Binaphthyl−Phosphino−Oxazoline Auxiliary: The Meta Dialkyl Effect on Enantioselectivity

Cooperative bimetallic catalysis in asymmetric allylic substitution

Strategies using a chiral metal catalyst and the cooperative effect of a second achiral or chiral metal catalyst for asymmetric allylic substitution reactions are discussed.

Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

A novel class of chiral phosphanyl-oxazoline (PHOX) ligands with a conformationally rigid cyclopropyl backbone was synthesized and tested in the intermolecular asymmetric Heck reaction. Mechanistic modelling and crystallographic studies were used to predict the optimal ligand structure and helped to design a very efficient and highly selective catalytic system. Employment of the optimized ligands in the asymmetric arylation of cyclic olefins allowed for achieving high enantioselectivities and significantly suppressing product isomerization. Factors affecting the selectivity and the rate of the isomerization were identified. It was shown that the nature of this isomerization is different from that demonstrated previously using chiral diphosphine ligands.

Determining the enantioselectivity of chiral catalysts by mass spectrometric screening of their racemic forms

The enantioselectivity of a chiral catalyst can be determined from its racemic form by mass spectrometric screening of a nonequal mixture of two mass-labeled quasienantiomeric substrates. The presented method opens up new possibilities for evaluating catalyst structures that are not readily available in enantiomerically pure form.

Metal-catalyzed enantioselective allylation in asymmetric synthesis

Metal-catalyzed enantioselective allylation, which involves the substitution of allylic metal intermediates with a diverse range of different nucleophiles or S(N)2'-type allylic substitution, leads to the formation of C-H, -C, -O, -N, -S, and other bonds with very high levels of asymmetric induction. The reaction may tolerate a broad range of functional groups and has been applied successfully to the synthesis of many natural products and new chiral compounds.

Platinum-Catalyzed Intramolecular Asymmetric Hydroarylation of Unactivated Alkenes with Indoles

[reaction: see text] A 1:1 mixture of the platinum bis(phosphine) complex [(S)-4]PtCl2 [(S)-4 = (S)-3,5-t-Bu-4-MeO-MeOBIPHEP] catalyzes the intramolecular asymmetric hydroarylation of 2-(4-pentenyl)indoles in moderate to good yield with up to 90% ee.

Conformational preferences driven by the C-methyl substituent in chelated o-diphenylphosphino-alpha-methyl-N,N-dimethylbenzylamine rhodium complexes

The stereochemistry of the chelate rings of a number of rhodium aminophosphine complexes is studied by NMR spectroscopy. The similarity in the variable-temperature behavior for the different compounds is consistent with them having in common highly preferred chelate ring conformations. The six-membered metallacycle of coordinated (R)-PN (PN = o-diphenylphosphino-alpha-methyl-N,N-dimethylbenzylamine) adopts a delta conformation in the solid state. NMR experiments indicate that this conformation is strongly favored in solution as well. The preferred sense of helicity is imposed by the absolute configuration of the stereogenic carbon atom on the ligand, which exerts an important steric control. The complex [Rh(TFB)((C(6)H(4)CHMeNMe(2))(2)P(C(6)H(4)CHMeNHMe(2)))](BF(4))(2).H(2)O.Me(2)CO crystallizes in the monoclinic space group P2(1) with a = 12.0548(11) A, b = 16.139(2) A, c = 12.1804(10) A, beta = 100.742(9) degrees, Z = 4.

Catalyzed Asymmetric Arylation Reactions

Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed.

Condensation of laterally lithiated o-methyl and o-ethyl benzamides with imines mediated by (-)-sparteine. Enantioselective synthesis of tetrahydroisoquinolin-1-ones

The first asymmetric synthesis of tetrahydroisoquinolin-1-ones using a (-)-sparteine-mediated lateral metalation-imine addition sequence to furnish 3-phenyl tetrahydroisoquinolinones 3a with enantioselectivities up to 81% ee is described (Scheme 4). For amide 7b, imine addition products 10 and 11 have been obtained with high diastereoselectivities (91-97% de) and enantioselectivities (91-98% ee) (Scheme 8).