Isothiocyanates reduction

Adducts from various quaternary salts have been isolated, in reactions with aldehydes, a-ketoaldehydes, dialkylacylphosphonates and dialkyl-phosphonates, isocyanates, isothiocyanates, and so forth (Scheme 15) (36). The ylid (11) resulting from removal of a Cj proton from 3.4-dimethyl-S-p-hydroxyethylthiazolium iodide by NEtj in DMF gives with phenylisothiocyanate the stable dipolar adduct (12) that has been identified by its NMR spectrum and reactional product, such as acid addition and thiazolidine obtention via NaBH4 reduction (Scheme 16) (35). It must be mentioned that the adduct issued from di-p-tolylcarbodiimide is separated in its halohydrogenated form. An alkaline treatment occasions an easy ring expansion into a 1,4-thiazine derivative (Scheme 17) (35). 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

The special properties of lipoic acid arise from the ring strain experienced by oxidized lipoic acid. The closed ring form is approximately 20 kj higher in energy than the open-chain form, and this results in a strong negative reduction potential of about —0.30 V. The oxidized form readily oxidizes cyanides to isothiocyanates and sulfhydryl groups to mixed disulfides. 

Alternatively, the thiazolotriazine ring was prepared from l-nitro-2-aminonaphthalene with an isothiocyanate to give naphthylpyrimidine 669, whose reaction with phenacyl bromide gave thiazoline 670. Reduction with stanous chloride and cyclization with (V-bromosuccinimide gave naphthothiazolotriazine 671 (74JIC631) (Scheme 138). 

Isocyanates and isothiocyanates are reduced to methylamines on treatment with LiAlH4. Lithium aluminium hydride does not usually reduce azo compounds (indeed these are the products from LiAlH4 reduction of nitro compounds, 19-59), but these can be reduced to hydrazo compounds by catalytic hydrogenation or with... 

Isoihamnetin la 323 Isothiazolone, microbiocidal la 45 Isothiocyanates la 75 lb 312 Isothiocyanate anions lb 307 Isotopes, detection limits la 41 Itaconic acid, reduction la 61 lodazide reaction lb 301,303... 

Richter utilized a reductive amination in their synthesis of the natural product (+)-hapalindole Q [294], Employing 10 equivalents of sodium cyanoborohydride and 40 equivalents of ammonium acetate in a methanol/THF mixture (150 °C, 2 min), the primary amine was obtained as a 6 1 mixture of diastereomers. Transformation to the isothiocyanate completed the total synthesis of (+)-hapalindole Q (Scheme 6.150). 

Following the strategy described above involving ipso-fhioro displacement and subsequent reduction, the resulting ortko-phenylenediamines were treated with several aromatic isothiocyanates in the presence of N,N -dicyclohexylcarbodiimide... 

Starting from the known isothiocyanate 351 <1998JHC29>, the cyclization of the semicarbazide 352, obtained from compound 351, by condensation with hydrazine hydrate, gives thione 353, whose nitrosation and reduction... 

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