Asymmetric Catalytic Cyanosilylation of Aldehydes Using a Chiral Binaphthol-Titanium Complex

✍ Scribed by Maki Mori; Hironori Imma; Takeshi Nakai

• Publisher: Elsevier Science
• Year: 1997
• Tongue: French
• Weight: 478 KB
• Volume: 38
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(97)01432-9

✦ Synopsis

The asymmetric cotalytic cyanosilylationof oliphaticaldehydes with Me3SiCN using (R)-BINOL-Ti(O-i-Pr)2 m an arymmem"c precakdyst is shown to proceed smoothly in dichloromethane to ~ford the cyanohydrinsin rekdvely high enantiose!ectivity (up @ 75~oee). @1997 Elsevier ScienceLtd.

Recently,much interest has been focusedon asymmetic catalysisby (R)-or (S)-1,1'-bi-2-naphthol (BINOL)-derived chid titanium complexes.l In ao effort to develop new BINOL-derivedasymmetric catalysts,we havecurrentlybeendevelopingnew asymmetriccatalysesby using(R)-BINOL-Ti(O-i-Pr)z (A)z as an asymmetricprecatalystthat is easily accessibleby simplymixingcommercially available(i-Pro)dTiand (R)-BINOL. Reportedso far iwethe asymmetriccatrdysesof the glyoxylate-enereaetionby complex B preparedvia completehydrolysisof complexA3and of the hydrosilylation of ketonesby complexC generated in situ from complexA and (EtO)+SiH.4In a continuationof these studies, we now wish to report the asymmetric catalyticcyanosilylation of aldehydeswith trimethylsilyl cyanide(TMSCN)usingcomplexA as an asymmetricprecatalyst, wherein the chid dicyanocomplexE in situ formed, not the initiallypostulated monoeyarto complexD, is likelyto serveas theactualasymmetric catalysts 83 :I ;. A, X, X=O-kPr(dimer) B, X2=0 (dimer) ;Tl:x C, X=H,X=O-i-Pr

:1 ;0 x D, X=CN, X=O-kPr E, X, X=CN