Optimized Syntheses of Optically Pure P-Alkene Ligands: Crystal Structures of a Pair of P-Stereogenic Diastereomers
Received: 19 January 2016
Accepted after revision: 26 January 2016
17 February 2016 (eFirst)
The ‘privileged’ P-alkene ligand (S)-2 is synthesized on a > 40 gram scale in 96% yield starting from dibenz[b,f]azepine-PCl2 (1; accessible on > 80 g scale) and (S)-BINOL. Similarly, the P-alkenes (R)-3 and the ‘chiral-at-P’ (SP ,SC )-4 are obtained from (R)-Taddol [(R,R)-α,α,α',α'-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol] and (S)-α,α-diphenylprolinol, respectively, in multigram quantities and high purity. The crystal structures of (SP ,SC )-4, its diastereomer (RP ,SC )-4, and of the (R)-SPINOL-derived ligand (R)-5 are reported. A slightly revised synthesis of SPINOL is also disclosed.