Ryo Shintani

A copper-catalyzed method for the regioselective 1,3-dipolar cycloaddition of azomethine imines to terminal alkynes has been developed. Through the use of a chiral phosphaferrocene-oxazoline ligand, a wide range of substrates can be coupled to generate useful heterocycles in very good enantiomeric excess.

Mopping up the rhodium: A rhodium-catalyzed asymmetric addition of arylboronic acids to isatins has been developed to produce biologically relevant 3-aryl-3-hydroxy-2-oxindoles in high yield (see scheme). High enantioselectivity was observed with (R)-MeO-mop as a ligand, and the reaction could be extended to the addition of alkenyl groups. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z600392_s.pdf or from the author. Please n

Two is better than one: Novel chiral phosphine–olefin ligands 1 a and 1 b act as bidentate ligands with some transition metals and have proved to be highly effective in the rhodium-catalyzed asymmetric 1,4-addition of aryl boronic acids to maleimides with high enantioselectivity (see scheme). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z501305_s.pdf or from the author. Please note: The publisher is not responsible for the co

A Pd-catalyzed asymmetric synthesis of Si-stereogenic dibenzosiloles is developed through enantioselective C-H bond functionalization of prochiral 2-(arylsilyl)aryl triflates. High chemo- and enantioselectivities are achieved by employing a Josiphos-type ligand under mild conditions.

Catalytic arylative cyclization of alkynals has been developed by the use of phosphine-free rhodium/diene complexes as catalysts. An asymmetric variant of this process has been successfully realized by employing a C2-symmetric chiral bicyclo[2.2.2]octadiene ligand. The rhodium/diene catalyst system is also effective for arylative cyclization of other substrates such as alkynones and enynes, achieving multiple carbon-carbon bond formations in a single step.

A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to substituted maleimides has been described. The regioselectivity in this reaction is controlled by the choice of ligand (dienes or bisphosphines), and 1,4-adducts with a quaternary stereocenter can be obtained with high regio- and enantioselectivity by the use of (R)-H8-binap.

A palladium-catalyzed desymmetrization of alkyne-tethered silacyclobutanes to give silacycles possessing a tetraorganosilicon stereocenter has been developed, and high chemo- and enantioselectivities have been achieved by the use of a newly synthesized chiral phosphoramidite ligand.

A new type of reagent, γ-methylidene-δ-valerolactones, has been devised, which acts as a four-carbon unit in a palladium-catalyzed cycloaddition reaction through the formation of a 1,4-zwitterionic species. The utility has been demonstrated in the context of stereoselective [4 + 3] cycloaddition with nitrones to provide highly functionalized 1,2-oxazepines, including the asymmetric variant with high enantioselectivity.

A planar-chiral Cu/phosphaferrocene–oxazoline catalyst mediates intramolecular Kinugasa reactions to give tricyclic β-lactams with good enantioselectivity. A variant of the process, in which a postulated enolate intermediate is intercepted with an electrophile in a transformation that generates two CC bonds, a CN bond, two new rings, a carbonyl group, and adjacent tertiary and quaternary stereocenters (see scheme), supports the proposed mechanism. Supporting information for this article is ava

A rhodium-catalyzed 1,4-addition of sodium tetraarylborates to beta,beta-disubstituted alpha,beta-unsaturated ketones is described. Highly efficient asymmetric catalysis has also been achieved by employing a readily available chiral diene ligand, leading to the construction of quaternary carbon stereocenters with high enantioselectivity.

A palladium-catalyzed [3 + 3] cycloaddition of trimethylenemethane (TMM) with azomethine imines has been developed to produce hexahydropyridazine derivatives under simple and mild conditions. The use of substituted TMM precursors highlights the difference of this system from previously reported [3 + 2] cycloaddition of TMMs under palladium catalysis. The present [3 + 3] cycloaddition reactions are also applicable to couplings with nitrones.

The asymmetric allylic substitution of allyl phosphates with aryl- and alkenylboronates catalyzed by a copper/N-heterocyclic carbene complex was developed and the γ-substitution products were obtained with high enantioselectivity (see scheme). To account for the observed influence of the reaction parameters a possible catalytic cycle for this process was proposed. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but n

[reaction: see text] A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to fumaric and maleic compounds has been developed. While phosphorus-based chiral ligands fail to induce high stereoselectivity, chiral norbornadiene ligands have proved to be uniquely effective to achieve high enantioselectivity in these 1,4-addition reactions.

A copper/N-heterocyclic carbene catalyzed hydroboration of carbon dioxide has been developed to give a formic acid derivative selectively under mild conditions. Investigations directed toward understanding the catalytic cycle of this process have been carried out, and the hydroboration product can be directly used as a formylation reagent for various amines.

A rhodium-catalyzed addition of sodium tetraarylborates to N-tosyl ketimines is described. Highly efficient asymmetric catalysis has been achieved by employing a chiral diene ligand, constructing chiral amine derivatives possessing α-tetrasubstituted carbon stereocenters with high enantioselectivity.