Thiocyanate group, reaction

The pairs of dyes more commonly used to generate FRET have been extensively reviewed [86-88] and their conjugation to different types of molecules has been facilitated by the incorporation of a range of reactive groups. Some examples are activated esters and iso thiocyanates for reaction with amino groups of proteins or peptides,... 

The glycosylations were carried out in dry dichloromethane in the presence of 0.1 equiv of triphenylmethylium perchlorate. It was assumed that the triphenylmethy-lium cation attacks the nitrogen of the thiocyanate group whereas the oxygen of the trityl ether attacks the anomeric carbon in a push-pull fashion. The trityl isothiocyanate formed was found to be unreactive under the reaction conditions. The disaccharide derivatives with (1-6), (1-4), (1-3) and (1-2) linkages have been obtained in good yields. 

The presence of a thiocyanate group can be very easily deduced from the IR spectrum, which contains a sharp, but weaker in intensity, IR band around 2150 cm-1 and an NMR carbon resonance between 112 and 115 ppm. In the case of psamaplin B (172), C-NMR additivity effects applied to the methylene carbon linked to the thiocyanate were used to distinguish between a thio- and isothiocyanate group [142]. Chemical proof can be provided by LAH reduction of the thiocyanate, which gives a thiol rather than a methylamine group as the reaction product of the reduction of the isothiocyanate [195]. 

Small amounts of the N-oxide of 8 accompanied the formation of o,o -dinitrodiphenylethane by the reaction of o-nitrotoluene with potassium rert-butoxide [73AC(P)329 75MI4]. Formation of 8 and its N-oxide also resulted from the controlled-potential electrolysis of o-nitrobenzyl thiocyanate, a reaction proceeding by dimerization of the initially formed onitrobenzyl radicals followed by simultaneous or subsequent reductive coupling of the nitro groups. In strongly acidic medium, the reaction took a different course (85CCC33). 

It seems likely that iodine attached to silicon might be replaced by chlorine with the aid of reagents such as AgCl or PbCla, but no such reactions have been reported. The replacement of chlorine by azide, cyanate, or thiocyanate groups does proceed readily, however (entry 35). 

Another example of sulfur abstraction by an osmium nitrido complex occurs in the reaction of [OsNC14]- with (PPh4)NCS to give (Ph4P)2[Os(NS)(NCS)3], in which the thiocyanate groups are thought to be bonded to the metal via nitrogen.265 For reactions of the complex see Scheme 10, p. 563. 

Thiocyanate groups may also be introduced by the cathodic substitution reaction discussed in Section IV, A, 1. 

Other examples of the cyanide as a leaving group are shown in Table 3 (entries 1-3). The chemistry shown in Table 3, entry 3, indicates that not only does nucleophilic substitution of a thiocyanate group displace the cyanide to form a thioether, but an extra equivalent of CH3MgI results in addition to the aldehyde and subsequent dehydrolysis to yield the final product. Typically addition to the cyanide group is competitive, with nucleophilic substitution resulting in a mixture of reaction products. 

Reactions with thiourea produce the corresponding thiones 167 (1968CR(C)128). The replacement of a chlorine atom with a thiocyanate group is also documented (1997AF1005). 

The apparent racemization in the formation of only trans- -p-nitro-thiophenoxypropenal from both cis- and thiocyanate group, which should be a worse leaving group than the halides, or to a post-isomerization reaction the necessary control experiments were not carried out. 

V-Chloropyrrole 1 is easily dehalogenated by potassium carbonate and cyanide ion (82JOC1008). The introduction of a thiocyanate group in position 2 of the pyrrole ring is achieved with thiocyanate ion. The reaction pro-... 

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