REACTIONS OF ETHOXY RADICALS WITH OPTICALLY ACTIVE TERTIARY PHOSPHINES. STEREOCHEMISTRY OF THE SUBSTITUTION PROCESS AND THE QUESTION OF PERMUTATION MODES FOR THE POSSIBLE PHOSPHORANYL RADICAL INTERMEDIATES.

Article abstract of DOI:10.1021/ja00357a016

The reactions were shown to yield substitution products MePhPOEt and n-PrMePOEt, respectively. Both reactions occur with net inversion of configuration at phosphorus. Optical yields are very sensitive to reaction times and conversions, because the product phosphonites are readily racemized by EtOH formed during reaction. If indeed these substitutions take place via phosphoranyl radicals, then the stereochemistry for reaction of (-)(S)-2 is consistent with the pi * electronic configuration and presumed tetrahedral geometry normally assigned to phenyl-substituted phosphoranyl radicals. Potential trigonal-bipyramidal intermediates are considered with the assumption that the EtO multiplied by (times) in initial adducts is apical and that the PhCH//2 departs exclusively from the apical position.