Chiral Bisphosphazides as Dual Basic Enantioselective Catalysts

Abstract

Chiral bisphosphazides complexed with lithium salts efficiently catalyze the direct enantioselective 1,4-addition of dialkyl malonates to acyclic enones. Spectroscopic studies on the stoichiometry of the bisphosphazide and lithium salt have indicated the formation of a 1:1 species as the active enantioselective catalyst. It is suggested that the catalyst generates a complex of the protonated phosphazide and the chiral nucleophile as the key intermediate. The phosphazide moiety appears to be a promising dual basic functionality for stereo- and chemoselective catalytic transformations.

Constrained‐Geometry Bisphosphazides Derived from 1,8‐Diazidonaphthalene: Synthesis, Spectroscopic Characteristics, Structural Features, and Theoretical Investigations

“…Four stable chiral C 2 ‐symmetric bisphosphazides with two interacting γ‐nitrogen atoms (Figure 1 f) have already been reported by Naka et al. who used them as catalysts for the conjugate addition of nucleophilic enols to enones 26. In the context of Naka’s work, the bisphosphazides were employed as Brønsted bases as well as Lewis bases forming 1:1 complexes with lithium salts.…”

“… Examples of phosphazides in the s ‐ trans 20 ( a ) and s ‐ cis ( b ) [15] conformations, stabilization of phosphazides by cyclization ( c ),8a incorporation into an azaphosphatrane cage ( d ),17 or coordination of a metal atom ( e ),11 and a chiral bisphosphazide able to act as an organocatalyst ( f ) 26…”

Recent Advances in H-Phosphonate Chemistry. Part 2. Synthesis of C-Phosphonate Derivatives

“…The protocol developed by Ooi et al [77] approaches the enantioselective synthesis of α-hydroxyphosphonate in a different way. This involves in situ formation of chiral dialkyl phosphite salt, a putative nucleophile in the Abramov reaction, from dialkyl H-phosphonate and a triaminoiminophosphorane [78], generated upon reaction of chiral tetraaminophosphonium salt TAP ( Fig. 2) with KOtBu.…”

One-pot insertion of chalcones into the benzoylacetone backbone

“…Active methylene compounds (AMC) are widely used as carbon nucleophiles in the coupling with e.g., chalcone (1,3-diphenyl-2-propen-1-one) to form extended ketones (Scheme 1) [6][7][8][9]. An intramolecular cyclization of these coupling products in Electronic supplementary material The online version of this article (doi:10.1007/s13738-015-0705-x) contains supplementary material, which is available to authorized users.…”