Chiral Ti(IV) complexes of hexadentate Schiff bases as precatalysts for aldehyde allylation: unusual additive effect of trimethylsilyl chloride

Chiral dinuclear titanium(IV) complexes have been found to be more effective catalysts for the asymmetric allylation of p-nitrobenzaldehyde than their mononuclear analogues. The addition of trimethylsilyl chloride to the reaction mixture decreases the rate of the background reaction and increases the yield of the reaction catalysed by the dinuclear complex.

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(S)-1-(4-Nitrophenyl)but-3-en-1-olC10H11NO3Ee = 74.0%[α]D25=-35.7 (c 0.5, CHCl3)Source of chirality: 3,3′-[((S)-1-hydroxymethyl-2-methylpropyl)imino]methyl-2,2′-dihydroxy-(S)-1,1′-binaphthaleneAbsolute configuration: (S)

3,3′-[((S)-1-Hydroxymethyl-2-methylpropyl)imino]methyl-2,2′-dihydroxy-(R)-1,1′-binaphthaleneC32H36N2O4Ee >99.9%[α]D25=-139.8 (c 1, CHCl3)Source of chirality: synthesis from (S)-valine and (R)-binolAbsolute configuration: (S,S,aR)

3,3′-[((S)-1-Hydroxymethyl-2-methylpropyl)imino]methyl-2,2′-dihydroxy-(S)-1,1′-binaphthaleneC32H36N2O4Ee >99.9%[α]D25=-163 (c 1, CHCl3)Source of chirality: synthesis from (S)-valine and (S)-binolAbsolute configuration: (S,S,aS)

3,3′-[((R)-1-Hydroxymethyl-2-methylpropyl)imino]methyl-2,2′-dihydroxy-(R)-1,1′-binaphthaleneC32H36N2O4Ee >99.9%[α]D25=+163 (c 1, CHCl3)Source of chirality: synthesis from (R)-valine and (R)-binolAbsolute configuration: (R,R,aR)

N-(2-Hydroxy-3,5-di-tert-butyl-benzylidene)-(S)-2-amino-3-methylbutan-1-olC20H33NO2Ee >99.9%[α]D25=-33.3 (c 0.78, MeOH)Source of chirality: synthesis from (S)-valineAbsolute configuration: (S)