T-Butyldimethylsilyl cyanide

Cyanosilylation. The Lewis acid-catalyzed reaction of t-butyldimethylsilyl cyanide (TBDMSCN) with aldehydes andke-tones affords the corresponding silylated cyanohydrins in good yield (eq 1). These have a greater stability than the silylated cyanohydrins obtained by using cyanotrimethylsUane The... 

Related Reagents. t-Butyldimethylsilyl Cyanide Hydrogen Cyanide. 

Reaction with Nucleophiles. TBDMSCl is the reagent of choice for the preparation of other TBDMS-containing reagents. For example, t-Butyldimethylsilyl Cyanide may be prepared by the reaction of TBDMSCl and Potassium Cyanide in acetonitrile containing a catalytic amount of Zinc Iodide TBDMSCN has also been prepared by treatment of TBDMSCl with KCN and 18-Crown-6 in CH2CI2 at reflux and by treatment of TBDMSCl with Lithium Cyanide prepared in situ. t-Butyldimethylsilyl Trifluoromethanesulfonate is prepared by treatment of TBDMSCl with Trifluoromethanesulfonic Acid at 60 °C. Other nucleophiles, such as thiolates, also react with TBDMSCl. t-Butyldimethylsilyl Iodide was prepared by treatment of TBDMSCl with Sodium Iodide in acetonitrile. In contrast to THF cleavage reactions using TMSI, the more stable TBDMS-protected primary alcohol may be i.solated from the reaction in eq 12. 

One general method for acyl silane synthesis particularly successful for a-cyclopropyl examples (and even an a-cyclobutyl example) involves treatment of acid chlorides with lithium tetrakis(trimethylsilyl) aluminum or lithium methyl tris(trimethylsilyl) aluminium and cuprous cyanide (vide supra, Section III.A.3)77. For example, cyclopropyl acyl silane (23) was obtained in 89% yield by this process. Improved procedures use lithium t-butyldimethylsilyl cuprate78 and a dimethylphenylsilyl zinc cuprate species79,80 as reagents. 

The way they solved the problem was this. (S )-(-)-Malic acid is available cheaply. Its dimethyl ester 127 could be chemoselectively reduced by borane to give 128. Normally borane does not reduce esters and clearly the borane first reacts with the OH group and then delivers hydride to the nearer carbonyl group. The primary alcohol was chemoselectively tosylated 129 and the remaining (secondary) OH protected with a silyl group 130 (TBDMS stands for t-butyldimethylsilyl and is sometimes abbreviated to TBS). Now the remaining ester can be reduced to an aldehyde 131 and protected 132. Displacement of tosylate by cyanide puts in the extra carbon atom 133 and reduction gives 134, that is the dialdehyde 126 in which one of the two aldehydes is protected. This compound was used in the successful synthesis of lipstatin. 

Addition to hindered ketones. With ZnU as catalyst the formation of cyanohydrin silyl ethers using either t-butyldimethylsilyl or t-butyldiphenylsilyl cyanide is remarkably efficient. 

Fluoropyrimidines 106 can be also synthesized using Diels-Alder reaction of fluorinated 2-aza-l,3-diene 105 with tosyl cyanide. The corresponding 2-aza-1,3-diene was easy synthesized from N-acylimldates 104 through silylation with t-butyldimethylsilyl triflate in a presence of triethylamine [125] (Scheme 23). 

Related Reagents. r-Butyldimethylsilyl Cyanide N-(t-Butyldimethylsilyl)-V-methyltrifluoroacetamide /-Butyldi-phenylchlorosilane Chlorotriphenylsilane r-Butyldimethylsilyl Trifluorosulfonate Triethylchlorosilane Trimethylchlorosilane Triisopropylsilyl Chloride. 

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