Solvent‐free cyanosilylation of aldehydes catalyzed by SmI₂

Abstract

A novel method to obtain racemic cyanohydrin silylethers by reaction of trimethylsilyl cyanide with a variety of aldehydes promoted by catalysis of SmI 2 is reported. The corresponding cyanosilylethers were obtained in high yields (up to 99%) in solvent-free conditions at room temperature within a relatively short time using 0.01-0.5 mol% catalyst loadings.

Activation of trimethylsilyl cyanide by potassium phthalimide for facile synthesis of TMS-protected cyanohydrins

“…Also, aromatic and aliphatic ketones, such as acetophenone or its 4-nitro derivative, 2-heptanone and cyclohexanone gave the corresponding cyanohydrins in high to quantitative yields. However, addition of TMSCN to ketones is slower in comparison with aldehydes due to more steric hindrance around the carbonyl group of ketones than of aldehydes (entries [16][17][18][19] [5,6].…”

“…The cyanosilylation of carbonyl compounds is particularly suitable since the silyl protecting groups can be removed under very mild reaction conditions. The cyanohydrin trimethylsilyl ethers are generally prepared by the addition of trimethylsilyl cyanide (TMSCN), a safe and easily handled reagent compared to HCN and KCN or NaCN [3][4][5][6]21,42], to carbonyl compounds in the presence of Lewis acids [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], inorganic Lewis bases [22][23][24][25], and double activating [3,26] or bifunctional catalytic systems [27][28][29]. However, many of these methods suffer from several disadvantages such as use of heavy and expensive metal catalysts [3,[12][13][14][15][16], high catalyst loading [6,13,14,22,23], the requirement for an inert atmosphere or anhydrous solvents [11][12][13]…”

“…Complete removing or replacement of a safer solvent in a chemical process is likely to often be the greatest reduction and simplification (in the work-up as well as the reaction) that can be achieved [52]. To the best of our knowledge, most of the introduced protocols for cyanosilylation of carbonyl compounds have been reported by using toxic solvents such as DMF [21,[43][44][45], CH 3 CN [1,12,[23][24][25], CHCl 3 [40] or CH 2 Cl 2 [11][12][13][14][15][16][17]19,26,[34][35][36][37][38][39]51] and the number of methods under solvent-free conditions remains quiet limited [5,6,18,33,49]. In continuation of our interest to develop new efficient nucleophilic organocatalysts for cyanosilylation of carbonyl compounds [33][34][35], we herein disclose the application of potassium phthalimide (PPI) as an efficient organocatalyst for the addition of TMSCN to carbonyl compounds under mild and solvent-free conditions affording various cyanohydrin trimethylsilyl ethers (Scheme 1).…”

Organocatalytic synthesis of cyanohydrin trimethylsilyl ethers by potassium 4‐benzylpiperidinedithiocarbamate under solvent‐free conditions

“…Accordingly, 2 mol% catalyst loading under solvent-free conditions at room temperature was found to be the optimal All products are known and were well-characterized by IR and NMR spectral data as compared with those obtained from authentic samples or reported in the literature. [9,12,17,18,20,21,35,50,54,70] c Determined by GC analysis.…”