Effective cyanosilylation of aldehydes with copper(II)-based polymeric catalysts

The new 1D copper(II) coordination polymers (CPs) [Cu(mu-L-1)(H2O)](n) (1, H2L1 = 2-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)benzoic acid) and [Cu(mu-H2L2)(H2O)](n) (2, H4L2 =(Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)terephthalic acid) and the known zwitterionic 1D CP [Cu-2(H2O)(2)(mu-H2L3)(mu-L-3)](n) (3, H3L3 = 2-(2-(4,4-dimethy1-2,6-dioxocyclohexylidene)hydrazinyl)terephthalic acid) were synthesized and tested as homogeneous catalysts for cyanosilylation of a variety of aldehydes to the corresponding cyanohydrin trimethylsilyl ethers. Among these polymeric catalysts, 3, with a zwitterionic charater, is the most effective one, giving 86-99% yield of the ethers upon reaction of aliphatic and aromatic aldehydes with trimethylsilyl cyanide in methanol at room temperature in 4 h. Non-covalent interactions (cation-pi and tetrel bondings) involving the aldehyde substrate are proposed to assist the cyanosilylation reaction. (C) 2016 Elsevier B.V. All rights reserved.