[56522-24-8] · C7H15NSi · t-Butyldimethylsilyl Cyanide · (MW 141.29)
Alternate Names: t-butylcyanodimethylsilane; TBDMSCN.
Physical Data: bp 163-167 °C/760 mmHg; mp 76-78 °C.
Solubility: sol organic solvents (methylene chloride, THF, chloroform); reacts rapidly with water and protic solvents.
Preparative Methods: conveniently prepared by refluxing t-Butyldimethylchlorosilane (1 equiv), Potassium Cyanide (1.3 equiv) and 18-Crown-6 (0.31 equiv) in dry methylene chloride under nitrogen.4 The reagent can also be prepared by the reaction of Silver(I) Cyanide with t-butyldimethylchlorosilane,2 or stirring at 60 °C for 4 h a mixture of sodium cyanide, Amberlite XAD-4 resin, and t-butyldimethylchlorosilane in acetonitrile.5
Handling, Storage, and Precautions: must be protected from moisture and handled in a well-ventilated fume hood. Exposure to water releases highly toxic HCN gas.
The Lewis acid-catalyzed reaction of t-butyldimethylsilyl cyanide (TBDMSCN) with aldehydes and ketones affords the corresponding silylated cyanohydrins in good yield (eq 1).1,6,7 These have a greater stability than the silylated cyanohydrins obtained by using Cyanotrimethylsilane. The addition of TBDMSCN to sterically hindered ketones proceeds smoothly in the presence of a catalytic amount of Zinc Iodide or potassium cyanide/18-crown-6 (eqs 2-4).8 A chelation-controlled stereoselective synthesis of silylated cyanohydrins has also been reported (eq 5).9
TBDMSCN silylates alcohols, phenols, and carboxylic acids efficiently and in high yield.2
Oxiranes undergo ring opening when refluxed with TBDMSCN/zinc iodide in methylene chloride, yielding isocyanides (eq 6).3 The rate of the oxirane ring opening is slower than the corresponding reactions with trimethylsilyl cyanide/zinc iodide.10
William C. Groutas
Wichita State University, KS, USA