Pd‐catalyzed asymmetric allylic substitution reactions using P‐chirogenic diaminophosphine oxides: DIAPHOXs

Abstract

This paper describes the development of a new class of chiral phosphorus ligand: aspartic acid-derived P-chirogenic diaminophosphine oxides, DIAPHOXs, and their application to several Pd-catalyzed asymmetric allylic substitution reactions. Pd-catalyzed asymmetric allylic alkylation was initially examined in detail using diaminophosphine oxides 1a, resulting in the highly enantioselective construction of quaternary stereocenters. Mechanistic investigations revealed that 1a is activated by N,O-bis(trimethylsilyl)acetamide-induced tautomerization to afford a trivalent diamidophosphite species 12, which functions as the actual ligand. Furthermore, asymmetric allylic amination was examined using Pd-DIAPHOX catalyst systems, providing a variety of chiral allylic amines.

Anionic phosph(in)ito (“phosphoryl”) ligands: Non-classical “actor” phosphane-type ligands in coordination chemistry

“…SPOs are generally easy to synthesize, and their air-and/or moisture stability allows long-term preservation and convenient handling [74][75][76][77]. Lately, these organophosphorus derivatives have drawn much attention.…”

Coordination chemistry and catalysis with secondary phosphine oxides

“…It is important to note that these special types of ligands have displayed excellent results in many palladium-and iridium-catalysed asymmetric processes providing high enantiomeric excesses, especially in asymmetric allylic substitution reactions. 43,[45][46][47][48][49] Scheme 11. Synthesis of the (S,RP)-DIAPHOX ligand.…”

“…279 These reactions have been applied to the formation of chiral centres in synthesis of biologically active products 285 and even to total syntheses. 284,286 It should be noted that Nemoto and Hamada 10,45,49 have reviewed the application of the DIAPHOX ligands to allylic substitution and the reader is directed to these reviews to have the full account of their applicability.…”

Development of New Methods in Organic Synthesis and Their Applications to the Synthesis of Biologically Interesting Natural Products

“…Although the enantioselectivity is moderate, it should be noted that the asymmetric metallo-ene reaction developed by us not only takes place under exceedingly mild conditions but also affords the highest enantiomeric excess in this area. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] Chiral trivalent phosphines including our phosphines, 9-PBN and 9-NapBN, have been well proven to be excellent ligands for transition metal-catalyzed reactions. These phosphines, however, bear an inherent weakness: sensitivity to air-oxidation.…”