Asymmetric 1,3-dipolar cycloaddition reaction of chiral 1-alkyl-1,2-diphospholes with diphenyldiazomethane

Abstract

The 1,3-dipolar cycloaddition of chiral 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes with diphenyldiazomethane leads to novel P-chiral bicyclic phosphiranes having six chiral centers.

Synthesis of P,P-bidentate caged phosphines via tungsten pentacarbonyl-promoted cycloaddition reactions of 1-alkyl-1,2-diphospholes

“…[13][14][15][16] The key structural feature of such phosphines is their rigid bi-or polycyclic framework, which eliminates the conformational flexibility inherent in other monocyclic chiral phosphines and represents a valuable motif for chiral ligand design. The efficiency of these ligands, featuring a chiral, nonracemizable bridgehead phosphorus atom was initially demonstrated by F. Mathey et al 17 The asymmetric [4+2] Diels-Alder cycloaddition reactions of 1-monophospholes [18][19][20] and 1,2diphospholes [21][22][23][24] with various dienophiles have become a classical approach to such rigid polycyclic phosphines. Using chiral Al 25 or Pd 26 complexes as the reaction promoters for the asymmetric [4+2] cycloaddition of monophospholes and 2-phosphindolizine has enabled the synthesis of a library of coordinated P-chiral phosphines.…”