Chiral nitrogen-containing compounds are widely distributed in nature and include many biologically important molecules (Chart 1). In these compounds, the nitrogen-containing units are known to play important roles for their bioactivities. For the synthesis of these chiral nitrogen-containing building blocks, use of imines as electrophiles is the most promising and convenient route.1 While many approaches using chiral imines or chiral nucleophiles have been reported,1 these diastereoselective reactions have some disadvantages. First, the procedures to introduce chiral auxiliaries to substrates and to remove them after the diastereoselective reactions are often tedious. Second, more than stoichiometric amounts of chiral sources are needed to obtain chiral compounds according to these reactions. On the other hand, catalytic enantioselective reactions provide the most efficient methods for the synthesis of chiral compounds,2 because large quantities of chiral compounds are expected to be prepared using small amounts of chiral sources. While much progress has been made recently in catalytic enantioselective reactions of aldehydes and ketones such as aldol,3 allylation,4 Diels-Alder,5 cyanation reactions,6 reduction,1b,2b etc., progress in catalytic enantioselective reactions of imines is rather slow. There are some difficulties in performing catalytic enantioselective reactions of imines. For example, in the cases of chiral Lewis acid promoted asymmetric Shū Kobayashi was born in 1959 in Tokyo, Japan. He studied chemistry at the University of Tokyo and received his Ph.D. in 1988 (Professor T. Mukaiyama). After spending 11 years at Science University of Tokyo (SUT), he moved to Graduate School of Pharmaceutical Sciences, University of Tokyo, in 1998. His research interests include development of new synthetic methods, development of novel catalysts (especially chiral catalysts), organic synthesis in water, solid-phase organic synthesis, total synthesis of biologically interesting compounds, and organometallic chemistry. He received the first Springer Award in Organometallic Chemistry in 1997.

https://chemistry.mdma.ch/hiveboard/picproxie_docs/000499541-cr980414z.pdf

Catalytic enantioselective addition to imines.

Lanthanide complexes in multifunctional asymmetric catalysis.

1,1‘-Binaphthyl Dimers, Oligomers, and Polymers: Molecular Recognition, Asymmetric Catalysis, and New Materials†

BINOL: A Versatile Chiral Reagent

The Henry reaction: recent examples

In a recent paper, the authors reported that Zr(O-t-Bu){sub 4} was an efficient and convenient basic reagent in organic synthesis. However, all reactions examined were performed with stoichiometric quantities of the reagent. The authors envisioned that rare earth metal alkoxides would be stronger bases than group 4 metal alkoxides due to the lower ionization potential (ca. 5.4-6.4 eV) and the lower electronegativity (1.1-1.3) of rare earth elements; thus, the catalytic use of rare earth metal alkoxides in organic synthesis was expected. Although a variety of rare earth metal alkoxides have been prepared for the last three decades, to the authors knowledge, there have been few reports concerning the basicity of rare earth metal alkoxides. Herein, the authors report several carbon-carbon bond-forming reactions catalyzed by rare earth metal alkoxides and their application to a catalytic asymmetric nitroaldol reaction.

Basic character of rare earth metal alkoxides. Utilization in catalytic C-C bond-forming reactions and catalytic asymmetric nitroaldol reactions

{alpha}-Amino phosphonic acids 3 are interesting compounds in the design of enzyme inhibitors. The concept of mimicking tetrahedral transition states of enzyme-medicated peptide bond hydrolysis previously led to the successful design and synthesis of phosphonamide-containing peptides as a promising new class of proteinase inhibitors. It is not surprising that the absolute configuration of the {alpha}-carbon strongly influences the biological properties of 3. Several methods for the synthesis of optically active {alpha}-aminophosphonic acids have been published. The authors report here the first example of a catalytic asymmetric hydrophosphonylation to imines using lanthanoid-potassium-BINOL heterobimetallic complexes (LnPB, Ln = lanthanoid metal), which gives optically active {alpha}-amino phosphonates in modest to high enantiometric excess. 17 refs., 1 tab.

Catalytic Asymmetric Synthesis of .alpha.-Amino Phosphonates Using Lanthanoid-Potassium-BINOL Complexes

Effects of rare earth metals on the catalytic asymmetric nitroaldol reaction

First catalytic asymmetric hydrophosphonylation of cyclic imines: Highly efficient enantioselective approach to a 4-thiazolidinylphosphonate via chiral titanium and lanthanoid catalysts

The authors studied catalytic effects of a Sm-(HDMS){sub 3} complex in the regioselective formation of a triple bond in prostaglandin precursors. The application of Sm(HMDS){sub 3} as a catalyst is novel. 4 tabs.

Shigeru Arai

Papers

Basic character of rare earth metal alkoxides. Utilization in catalytic C-C bond-forming reactions and catalytic asymmetric nitroaldol reactions

Catalytic Asymmetric Synthesis of .alpha.-Amino Phosphonates Using Lanthanoid-Potassium-BINOL Complexes

Effects of rare earth metals on the catalytic asymmetric nitroaldol reaction

First catalytic asymmetric hydrophosphonylation of cyclic imines: Highly efficient enantioselective approach to a 4-thiazolidinylphosphonate via chiral titanium and lanthanoid catalysts

Catalytic aldol reaction with Sm(HMDS)3 and its application for the introduction of a carbon-carbon triple bond at C-13 in prostaglandin synthesis