Homochiral catalysts that can effect asymmetric transformations are invaluable in the production of optically active molecules. Researchers are actively pursuing the design of new ligands and organocatalysts by exploiting concepts derived from the application of bifunctional and C2-symmetric catalysts. Many homochiral catalysts containing amines, ethers, alcohols, and phosphines as electron-pair donors have been successfully developed.Amine N-oxides are highly polar substances. Despite their pronounced capacity as electron-pair donors, N-oxides have been underutilized in asymmetric reactions; they have only made a visible impact on the field in the preceding decade. Systematic studies have instead largely focused on pyridine- or quinoline-based scaffolds in organosilicon and coordination chemistry. The application of chiral tertiary amine N-oxides has not been widely pursued because of the difficulty of controlling the chirality at the tetrahedral nitrogen of the N-oxide moiety. In this Account, we outlin...

Chiral N,N′-Dioxides: New Ligands and Organocatalysts for Catalytic Asymmetric Reactions

The preparation of highly functionalized organometallic compounds can be achieved by direct C-H activation of a broad range of unsaturated substrates using lithium chloride solubilized 2,2,6,6-tetramethylpiperidide bases (TMP(n)MX(m)⋅p LiCl). These are excellent reagents for converting a wide range of aromatic and heterocyclic substrates into valuable organometallic reagents with broad applications in organic synthesis.

Regio- and chemoselective metalation of arenes and heteroarenes using hindered metal amide bases.

The metal-catalyzed asymmetric addition of phosphorus nucleophiles is one of the most efficient and reliable approaches for the construction of new carbon–phosphorus bonds. In recent years, great achievements have been made in this area, and many powerful methods have been developed for these transformations with high efficiency, low ligand loading and excellent selectivity. This tutorial review covers recent efforts in the constructions of P–C bonds through asymmetric additions of phosphorus nucleophiles including dialkyl phosphites, secondary phosphine oxides and secondary phosphines.

Recent developments in metal catalyzed asymmetric addition of phosphorus nucleophiles

The metal-catalyzed asymmetric conjugate addition (ACA) reaction has emerged as a general and powerful approach for the construction of optically active compounds and is among the most significant and useful reactions in synthetic organic chemistry In recent years, great progress has been made in this area with the use of various chiral metal complexes based on different chiral ligands This review provides comprehensive and critical information on the enantioselective 1,4-conjugate addition of nonorganometallic (soft) nucleophiles and their importance in synthetic applications The literature is covered from the last 10 years, and a number of examples from before 2007 are included as background information The review is divided into multiple parts according to the type of nucleophile involved in the reaction (such as C-, B-, O-, N-, S-, P-, and Si-centered nucleophiles) and metal catalyst systems used

Recent Advances in Metal-Catalyzed Asymmetric 1,4-Conjugate Addition (ACA) of Nonorganometallic Nucleophiles.

The conjugate addition reaction of carbon nucleophiles to electron-deficient olefins is one of the most reliable methods for selective C–C bond formation. However, the conjugate addition to the vinylogous electron-deficient dienes has been much less developed, as there is considerably more difficulty in controlling the regioselectivity of the addition to these extended conjugate systems due to the presence of three electrophilic sites, as well as the stereoselectivity. Although still underdeveloped, new approaches to tackle these challenges are beginning to emerge. Both transition-metal-catalyzed and organocatalytic approaches are currently being developed to cope with the main selectivity issues of this type of process: regioselectivity (1,2-, 1,4-, and 1,6-addition) and stereoselectivity (asymmetric formation of the new C–C bonds). In this tutorial review, we have surveyed representative examples to get an overview of the recent advances obtained in the scope of the conjugate addition reaction of carbon nucleophiles to electron-deficient dienes.

Conjugate addition reactions of carbon nucleophiles to electron-deficient dienes

Highly enantioselective hydrophosphonylation of aldehydes catalyzed by tridentate Schiff base aluminum(III) complexes.

The conjugate addition of carbon nucleophiles to nitroalkenes is an important synthetic process in organic synthesis mainly because of the large range of subsequent possible transformations of the nitro group. The generation of optically active 1,3-dinitro compounds is an attractive facet of this research area because they are precursors of enantioenriched 1,3-diamines, which can serve as versatile building blocks for pharmaceutical compounds. However, enantioselective versions of these processes have only just started to emerge. In 2006, Du and co-workers reported the direct asymmetric Michael addition of nitroalkanes to nitroalkenes by using zinc(II)bis(oxazoline) and -bis(thiazoline) complexes as catalysts. Wang et al. showed that a modified cinchona alkaloid was a useful asymmetric catalyst for the synthesis of 1,3-dinitroalkanes. Subsequently, the Maruoka research group revealed that N-spiro chiral ammonium bifluorides could efficiently catalyze the asymmetric Michael addition with silyl nitronates. Despite these important contributions, the development of new and efficient asymmetric catalytic systems is still an interesting challenge. N,N’Dioxides have been successfully applied as excellent chiral scaffolds in many asymmetric reactions. Moreover, the electropositive properties and high coordination ability of lanthanide ions has resulted in them attracting significant attention in organic synthesis. Herein, we describe the direct asymmetric Michael addition of unmodified nitroalkanes to nitroalkenes by using lanthanum(III) triflate in combination with an N,N’-dioxide ligand. Initially, N,N’-dioxide L1 (Scheme 1) was complexed in situ with various metal salts to catalyze the Michael addition in the presence of iPr2NEt. [14] The metal source had a decisive effect on the enantioslectivity of the reaction. As shown in Table 1, the Cu, In, and Sc complexes of N,N’-dioxides successfully employed in other asymmetric reactions only gave extremely poor results in the Michael reaction (Table 1, entries 1–3). Furthermore, although the Cu and Ni complexes showed excellent activating ability for the nitroolefins, their N,N’-dioxide complexes catalyzed the

Highly Enantioselective Direct Michael Addition of Nitroalkanes to Nitroolefins Catalyzed by La(OTf)3/N,N′‐Dioxide Complexes

Highly Enantioselective Hydrophosphonylation of Aldehydes Catalyzed by Tridentate Schiff Base Aluminum(III) Complexes.

Efficient enantioselective hetero-Diels-Alder reaction of Brassard's diene with aliphatic aldehydes: a one-step synthesis of (R)-(+)-kavain and (S)-(+)-dihydrokavain.

Highly Enantioselective Direct Michael Addition of Nitroalkanes to Nitroolefins Catalyzed by La(OTf)3/N,N′‐Dioxide Complexes.

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