Tetrabutylammonium thiocyanate

The bicyclic 1,6-anhydroglucose 140 is a versatile synthetic intermediate readily prepared by pyrolysis of corn starch and can be derivatized at the anomeric position by use of Lewis acid activators (Scheme 6.23) [70, 71], For example, treatment with tetrabutylammonium thiocyanate in the presence of BF3 OEt2 leads to isothiocyanate 141, which was subsequently employed by Carreira in the preparation of (+)-trehalozin (142), a potent glyco-sidase inhibitor [71]. 

The Fischer method7 for preparation of sugar isothiocyanates is general however, many modifications have been introduced, using, for example, nonpolar solvents and silver thiocyanate,29 33 lead thiocyanate,33 or ammonium thiocyanate,34 and potassium thiocyanate in acetonitrile in the presence of tetrabutylammonium hydrogensulfate.34 ... 

NCS)2] (51), and TBA[Ir(ppy)2(NCO)2] (52). These complexes were conveniently synthesized under inert atmosphere by reaction between the dichloro-bridged Ir dimer [Ir(ppy)2(Cl)]2 in dichloromethane solvent with an excess of a pseudohalogen ligand such as tetrabutylammonium cyanide, tetrabutyl-ammonium thiocyanate, or tetrabutylammonium isocyanate, respectively, with over 70% yields [77]. 

When tetrabutylammonium 4-methoxyphenyltrichloroiodotellurate(IV) and four molar equivalents of silver thiocyanate were refluxed in chloroform for four hours, the tetra(thiocyanato)tellurate( V) was obtained upon concentrating the solution3. 

Advances of the past three decades, however, have produced alternatives to the heavy metal-based cellulose solvents. Prominent among them are dimethylacetamide/LiCl (DMAc/LiCl) N,MMN-0 hydrate (NMMO) tetrabutylammonium fluoride/DMSO (TBAF/DMSO) and potassium thiocyanate/DMSO [48]. While many of these solvents have gained significant popularity among laboratory chemists, only the amine oxide solvent, N,MMNO, has achieved industrial practicality. This will be discussed in the section on regenerated cellulose fibers. Several other important physical properties of cellulose are given in O Table 4. 

CAUTION Tetrabutylammonium bromide is an irritant. Handle with care It is also hygroscopic and should be protected from moisture prior to its use. Dispense the toluene and the thiocyanate solution in the hood using automatic delivery pipets. 

Kitamura, T., Kobayashi, S., and Taniguchi, H., Photolysis of vinyl bromides in the presence of tetrabutylammonium azide trapping of a vinyl cation with azide ion. Tetrahedron Lett., 1619,1979. (a) Kitamura, X, Kobayashi, S., and Taniguchi, H., Reaction of photogenerated vinyl cations with ambident anions, Chem. Lett., 1523, 1984 (b) Kitamura, X, Kobayashi, S., and Taniguchi, H., Photolysis of vinyl halides. Reaction of photogenerated vinyl cations with cyanate and thiocyanate ions,/. Org. Chem., 55, 1801, 1990. 

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