Isothiocyanates isocyanates

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). 

Other Reactions. 2-Dioxolaniniines, 2-oxathiolaniniines, and 2-oxa2o1idinimines result from the reaction of propylene oxide with isocyanates, isothiocyanates, and carbodiimides, respectively (103,104). 

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. 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

Few of the many other inorganic compounds of Ge, Sn and Pb call for special comment. Many pseudo-halogen derivatives of Sn, Pb and Pb have been reported, e.g. cyanides, azides, isocyanates, isothiocyanates, isoselenocyanates and alkoxides. ... 

Isopropylcumyl hydroperoxide, >72% in solution Isopropyl isocyanate Isothiocyanic acid... 

Synthesis of Isocyanates, Isothiocyanates, Aminoisocyanates, Aminoisothiocyanates, and A-Sulfinylamines... 

Analogous to the synthesis of isocyanates, isothiocyanates are obtained in good yield by reacting AyV -thiocarbonyldiimidazole (ImCSIm) with primary aliphatic or aromatic amines in equimolar amount. In chloroform at room temperature the dissociation equilibrium of imidazole-A-thiocarboxamides is shifted completely to isocyanates. 

Itoh and co-workers reported the ruthenium(n)-catalyzed [2 + 2 + 2]-cycloaddition of 1,6-diynes with isocyanates to afford the corresponding bicyclic pyridones 163 (Scheme 72).356 357 For previously reported ruthenium-catalyzed [2 + 2 + 2]-cycloaddition of 1,6-diynes see Refs 358 and 358a, and for theoretical calculations of the cyclocotrimer-ization of alkynes with isocyanates, isothiocyanates, and carbon disulfide see Refs 359 and 359a. 

Koenig GM, Wright AD, Angerhofer CK. (1996) Novel potent antimalarial diterpene isocyanates, isothiocyanates, and isonitrile from tropical marine sponge Cymbastela hooperi. J Org Chem 61 3259-3267. 

In contrast to 4-alkyl-5-sulfonylimino-A -l,2,3,4-thiatriazolines (58) (Section 4.19.5.1.2), 4-alkyl-5-alkylimino-A -l,2,3,4-thiatriazolines (50) react with immediate nitrogen evolution when added to electron-rich alkenes or to heterocumulenes such as enamines, carbodiimides, isocyanates, isothiocyanates, or styrene. Reaction kinetics for certain of this type of system show that they undergo bimolecular processes as described below. 

Iminophosphoranes have also proved to be key intermediates because they react with carbonyl compounds, isocyanates, isothiocyanates, acid chlorides, carbon dioxide, and carbon disulfide to give a wide range of imines and heterocumulenes, which are intermediates to pteridines. The preparation of iminophosphoranes has been investigated... 

Amidines formed by condensation of 4-aminouracils with dimethylformamide dimethyl acetal are effective dienophiles, and form pyrimido[4,5-rflpyrimidines by [4-I-2] cycloaddition with isocyanates, isothiocyanates (Equation 83) <2005TL1433> and imines (Equation 84), A similar process has also been reported, using a nitrone as the dienophile (Equation 85) <2006BMCL3537>. 

N-Vinyl heterocumulenes represent a new, highly reactive 2-azadiene species, which react, in general, with electron-rich alkenes and alkynes. Accordingly, we think it is of interest to complement the utility of electron-poor 2-azadienes in [4 + 2] cycloadditions by showing some examples involving A-vinyl isocyanates, -isothiocyanates, -carbodiimides, and -ketenimines. 

In contrast to isocyanates, isothiocyanates are relatively unreactive toward hydroxyl-containing compounds thus they are not even affected by aqueous media [31]. Their reaction with hydroxyalkyl thioureas has been reported [32]. With free 2-mercaptoethylamine, 1 mole of phenyl isothiocyanate gave the N-substituted product, l-(2-mercaptoethyl)-3-phenyl-2-thiourea, and 2 moles gave the N,S-disubstituted product. Isocyanates, regardless of the relative amounts, reacted with 2-mercaptoethylamine to give the N,S-disubsti-tuted products. Cleavage with silver nitrate affords the l-(2-mercaptoethyl)-3-alkylureas [33]. 

Oxidative cleavage of amines 9-39 Reduction of amides 9-47 Reduction of nitro compounds 9-50 Reduction of nitroso compounds or hydroxylamincs 9-51 Reduction of oximes 9-52 Reduction of azides 9-53 Reduction of isocyanates, isothiocyanates, or N-nitroso compounds 9-55 Reduction of amine oxides 9-59 Reduction of azo, azoxy, or hydrazo compounds... 

Several resins have been used frequently in reactant sequestration. Ami-nomethylpolystyrene 1 and the more highly functionalized polyamine resins 2 and 3 have been reported to sequester excesses of solution-phase electrophiles, including isocyanates, isothiocyanates, sulfonyl chlorides, acid chlorides, anhydrides, aldehydes, and imines. Cross-site reactivity is not an issue with the more densely functionalized sequestering resins so their use in an automated laboratory environment offers a significant resin and volume economy compared to less densely functionalized resins. 

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. 

The Chemistry of Acyl and Sulphonyl Isocyanates, Isothiocyanates, and Isoselenocyanates ... 

Although marine organisms produce a large number of isocyanates, isothiocyanates, and formamides, the corresponding thiocyanates have rarely been encountered. Indeed, the thiocyanate functionality has only been found in six sesquiterpenes (263-268), in four tricyclic quinoline alkaloids (271-274), and in psamaplin B (172) (included in the bromotyrosine derivatives discussed in the disulfide/polysulfide section). They have been found in marine sponges, as well as in nudibranches and tunicates. 

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