Asymmetric ring opening of epoxides with cyanides catalysed by chiral binuclear titanium complexes

A series of Schiff bases obtained from salicylaldehydes and 3,3′-diformyl-BINOL were synthesized. The complexes of these Schiff bases with Ti(IV) were active for the asymmetric ring opening of epoxides with TMSCN. A mixture of unpurified ligands was found to be as effective as the best one. The influence of temperature, solvent polarity and structural modification of the pre-catalysts on the enantioselectivity of the process has also been investigated.

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(R)-3,3′-Bis((((1R,2R)-2-((-2-hydroxybenzylidene)amino)cyclohexyl)imino)methyl)-[1,1′-binaphthalene]-2,2′-diolee >99%[α]D25 = −352 (c 0.62, CHCl3)Source of chirality: synthesis from (R,R)-cyclohexanediamine and (Ra)-BINOLAbsolute configuration: (R,R,Ra,R,R)

(R)-3,3′-Bis((((1R,2R)-2-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino)cyclohexyl)imino)methyl)-[1,1′-binaphthalene]-2,2′-diolee >99%[α]D25 = −386 (c 0.5, CHCl3)Source of chirality: synthesis from (R,R)-cyclohexanediamine and (Ra)-BINOLAbsolute configuration: (R,R,Ra,R,R)

(51R,52R,121R,122R)-4,6,11,13-Tetraaza-1,2,9(1,3),8(3,1)-tetranaphthalena-5,12(1,2)-dicyclohexanacyclotetradecaphane-3,6,10,13-tetraene-12,22,82,92-tetraolee >99%[α]D25 = −214 (c 0.25, CH2Cl2)Source of chirality: synthesis from (R,R)-cyclohexanediamine and (Ra)-BINOLAbsolute configuration: (R,R,Ra,R,R)