P-chiral, monodentate ferrocenyl phosphines, novel ligands for asymmetric catalysis.
Eight P-chiral monodentate ferrocenyl phosphines (1a-h) were prepared in high enantiomeric excess (>95% ee in most cases) by way of an ephedrine-based oxazaphospholidine borane complex. Primary alkyl, secondary alkyl, and substituted aromatic substituents were successfully introduced at the phosphorus center, along with ferrocenyl and phenyl groups, generating phosphines of the general structure FcP(Ph)(R) (Fc = ferrocenyl, R = aryl, alkyl). The synthetic route employed provides facile access to a previously undeveloped class of chiral monophosphines. These compounds were evaluated as ligands in asymmetric catalytic reductive coupling of alkynes and aldehydes and were found to provide the desired chiral allylic alcohols with good regioselectivity and ee in many cases and with complete (E)-selectivity (>98:2) in all cases.
Colby
Elizabeth A
EA
Massachusetts Institute of Technology, Department of Chemistry, Cambridge, Massachusetts 02139, USA.
Jamison
Timothy F
TF
D000438:Alcohols / Q000737:chemistry; D000447:Aldehydes / Q000737:chemistry; D000480:Alkynes / Q000737:chemistry; D001880:Boranes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D010720:Phosphines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000438:Alcohols; D000447:Aldehydes; D000480:Alkynes; D001880:Boranes; D005296:Ferrous Compounds; D008024:Ligands; D010720:Phosphines