Enantioselective synthesis of α-phosphanyl ketones and 2-phosphanyl alcohols

Article abstract of DOI:10.1002/jlac.199719970212

An efficient, highly enantioselective methodology for the synthesis of α-phosphanyl ketones 7 and 2-phosphanyl alcohols 12 and 13, important hemilable ligands for enantioselective homogeneous catalysis and chiral building blocks in general, has been developed. The key step of this first enantioselective synthesis of α-phosphanyl ketones is the diastereoselective phosphanylation of SAMP hydrazones 2 to produce α-phosphanyl hydrazones, isolated as the more stable borane adducts 6. Subsequent ozonolysis afforded α-phosphanyl ketones 7. The enantioselective synthesis of 2-phosphanyl alcohols 12 and 13 has been accomplished by two fundamentally different procedures: the phosphanylation of unsubstituted chiral aldehyde hydrazones 9 and the alkylation of α-diphenylphopshanyl acetaldehyde SAMP hydrazone 10. After separation of the minor diastereomer, the borane-protected α-phosphanyl aldehyde hydrazones 11 were converted to unprotected 2-phosphanyl alcohols 13 by ozonolysis, reduction and removal of the borane group. The absolute configuration of the functionalized phosphanes was determined by X-ray analysis, NOE experiments or polarimetry. VCH Verlagsgesellschaft mbH, 1997.