TMSCN

The regiochemistry of this transformation can be controlled by the choice of Lewis acid. In another substrate the use of ZnBr2/TMSCN gives the cyanohydrin at the more substituted hydroxyl, whereas the use of TiCl4as a Lewis acid places the cyanohydrin at the least substituted hydroxyl. " ... 

TMSCN, CHjClj, Yb(OTf)3, 55-95% yield. Aromatic ketones fail to... 

TMSCN, CH3CN, reflux, 2 h, 89-95% yield.These conditions are selective for aldehydes. 

TMSCN, (—)-DIPT [diisopropyl L-tartrate], Ti(/-PrO)4, CH2CI2, 0°, 6 h, rt, 12 h, 95% yield. These conditions afford chiral cyanohydrins. ... 

Chiral (salene)Ti(IV) complexes, TMSCN. This system is selective for aldehydes the asymmetric induction is dependent upon aldehyde struc-... 

Photolysis with visible light, DAP " TMSCN. The photochemical reaction generates an iminium ion that is trapped with cyanide."... 

Addition of the alcohol 42 to a solution of BF3 Et20/TMSCN in DCM provided the nitrile 43 in 83% yield. Hydrolysis of nitrile 43 then furnished amide 44 in 85% yield. Demethylation of the methoxyindole 44 with BBra in DCM provided the hydroxyindole 45 in 80% yield. This was followed by alkylation of 45 with the bromide 46 under phase transfer conditions to provide the phosphonate ester 47 and subsequent cleavage of the methyl ester by TMS-I furnished trimethylsilyl phosphonic acid 48, which upon alcoholic workup afforded LY311727. 

Method A TMSCN, Et3N, EtOH Method B Et3NH+ CN ... 

Jacobsen developed a method employing (pybox)YbCl3 for TMSCN addition to meso-epoxides (Scheme 7.22) [46] with enantioselectivities as high as 92%. Unfortunately, the practical utility of this method is limited because low temperatures must be maintained for very long reaction times (up to seven days). This reaction displayed a second-order dependence on catalyst concentration and a positive nonlinear effect, suggesting a cooperative bimetallic mechanism analogous to that proposed for (salen)Cr-catalyzed ARO reactions (Scheme 7.5). 

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