Catalytic asymmetric hydrosilylation of ketones with new chiral ferrocenylphosphine-imine ligands

✍ Scribed by Tamio Hayashi; Chihiro Hayashi; Yasuhiro Uozumi

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 242 KB
• Volume: 6
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/0957-4166(95)00326-k

✦ Synopsis

New chiral ferrocenylphosphines containing an imino group on the side chain, (S)-N-alkylidene-l-[(R)-2-diphenylphosphinoferrocenyl]ethylamines, were prepared by condensation of (S)-l-[(R)-2-diphenylphosphinoferrocenyl]ethylamine with aromatic aldehydes. The imino-phosphine ligands were found to be very effective for rhodium-catalyzed asymmetric hydrosilylation of prochiral ketones with diphenylsilane to give optically active alcohols of up to 90% ee.

We have developed homochiral ferrocenylphosphines I which are effective as ligands for several types of asymmetric reactions catalyzed by transition metal complexes. 2 The ferrocenylphosphines have been demonstrated to be superior to others in that both monophosphines and 1,1'-bisphosphines can be readily prepared and structural modification can be readily made by introduction of a desired functional group on the side chain according to the demand of the reaction type. By this modification, the ferrocenylphosphines can bring about high enantioselectivity in a variety of catalytic asymmetric reactions, including rhodium(I)-catalyzed hydrogenation, 3 palladium(0)-catalyzed allylic substitution reactions,4, 5 and gold(I)-or silver(I)-catalyzed aldoltype reactions of isocyanocarboxylates.6,7,8 Here we report that high enantioselectivity can be attained in the rhodium-catalyzed asymmetric hydrosilylation of ketones by use of new ferrocenylmonophosphines where an imino group was introduced on the ferrocenylmethyl position. Scheme 1 Me Me Me Me2N ~ AcO~ H2N ~ ,:7-"-Hph2P~'-/~ *C 100 *C (S)-(R)-PPFA (2) (S)-(R)-PPFOAc (S)-(R)-PPFNH 2 (3)