Halides isothiocyanates

Sugar thiocyanates rearrange more or less readily into the corresponding isothiocyanates.8,20 23 According to the first comprehensive article24 concerned with the isomerization of organic thiocyanates into isothiocyanates, halides may react either by an SnI or an Sn2 mechanism. The SnI mechanism gives rise to the thiocyanate, which may isomerize to an isothiocyanate. 

CH rCHCH NHCSNH. Colourless crystalline solid with a faint garlic-like odour m.p. 74 C. Manufactured by treating propenyl isothiocyanate with a solution of ammonia in alcohol. It has been given by injection in the treatment of conditions associated with the formation of excessive fibrous tissue. Toxic side reactions may occur. Propenyl thiourea is a chemical sensitizer for photographic silver halide emulsions. 

Azoles containing a free NH group react comparatively readily with acyl halides. N-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (66) -> (67) or type (70)->(71) or (72). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. When two isomeric products could result, only the thermodynamically stable one is usually obtained because the acylation reactions are reversible and the products interconvert readily. Thus benzotriazole forms 1-acyl derivatives (99) which preserve the Kekule resonance of the benzene ring and are therefore more stable than the isomeric 2-acyl derivatives. Acylation of pyrazoles also usually gives the more stable isomer as the sole product (66AHCi6)347). The imidazole-catalyzed hydrolysis of esters can be classified as an electrophilic attack on the multiply bonded imidazole nitrogen. 

Paralleling the various phosphorus trihalides are numerous pseudohalides and mixed pseudohalide-halides of which the various isocyanates and isothiocyanates are perhaps the best known. Most are volatile liquids, e.g. 

When the reagent is the thiocyanate ion, S-alkylation is an important side reaction (10-43), but the cyanate ion practically always gives exclusive N-alkylation. ° Primary alkyl halides have been converted to isocyanates by treatment with sodium nitrocyanamide (NaNCNN02) and m-chloroperoxybenzoic acid, followed by heating of the initially produced RN(N02)CN. ° When alkyl halides are treated with NCO in the presence of ethanol, carbamates can be prepared directly (see 16-7). ° Acyl halides give the corresponding acyl isocyanates and isothiocyanates. For the formation of isocyanides, see 10-111. 

Reactions of Heterocyclic N-Oxides with Trimethylsilyl Cyanide, Trimethylsilyl Azide, Trimethylsilyl Isothiocyanate, and Trimethylsilyl Halides... 

The sodium salts of dialkyl malonates were reacted with isothiocyanates (346) in diethyl ether or in THF at -10°C-0°C. The products were then alkylated with alkyl halides to give mixtures of tautomeric (alkylthio)ami-... 

The reactions of Meldrum s acid (421) and acyl isothiocyanates in DMSO in the presence of lithium hydride at ambient temperature for 2-3 hr gave the lithium salts (457), which were alkylated by treatment with alkyl halide for 5 hr to afford isopropylidene (acylamino)(alkylthio)methy-lenemalonates (458) in 20-90% yields (87ZC68). 

Primary amines R1NH2 are converted into isothiocyanates by the action of carbon disulphide and alkyl halides R2X in the presence of DBU (equation 113)370. 

Numerous d cobalt(III) complexes are known and have been studied extensively. Most of these complexes are octahedral in shape. Tetrahedral, planar and square antiprismatic complexes of cobalt(lII) are also known, but there are very few. The most common ligands are ammonia, ethylenediamine and water. Halide ions, nitro (NO2) groups, hydroxide (OH ), cyanide (CN ), and isothiocyanate (NCS ) ions also form Co(lII) complexes readily. Numerous complexes have been synthesized with several other ions and neutral molecular hgands, including carbonate, oxalate, trifluoroacetate and neutral ligands, such as pyridine, acetylacetone, ethylenediaminetetraacetic acid (EDTA), dimethylformamide, tetrahydrofuran, and trialkyl or arylphosphines. Also, several polynuclear bridging complexes of amido (NHO, imido (NH ), hydroxo (OH ), and peroxo (02 ) functional groups are known. Some typical Co(lll) complexes are tabulated below ... 

The active hydrogens of pseudoureas react with various reagents, such as sodium hypochlorite [72], acyl halides [73], sulfonyl halides [19], isocyanates [26], isothiocyanates [26, 74] cyanamide, [75] and esters [76], to give linear or cyclic derivatives as shown in Scheme 2. 

Azoles containing a free NH group react comparatively readily with acyl halides. yV-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (75) — (76) or type (79)—>(80) or (81). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. 

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