Reactions with Isocyanates and Isothiocyanates

Thongh different bonds are made, it is useful to include here the enaminothioimidate shown below for the synthesis of pyrimidin-2-ones and -thiones, by reaction with isocyanates and isothiocyanates, respectively, proceeding via a cycloaddition between the azadiene and the imine unit of the -N=C=S, then loss of dimethylamine to aromatise. ... 

In Section 1.2, we indicated that the nucleophilic properties of dimethoxy-carbene could be put to synthetic use for example in the synthesis of heterocyclic compounds by reactions with isocyanates and isothiocyanates. [23,24] It is worth noting that analogous chemistry is being elaborated by Rigby s group forthebis(alkylthio)carbenes e.g., ( -PrS)2C. [109] Obviously, the nucleophilic properties of (RS)2C parallel those of (MeO)2C. Moreover, further manipulation of the alkythio groups in the products of (RS)2C reactions opens substantial synthetic opportunities. [109]... 

The reaction of enamino ketones with isocyanates and isothiocyanates has not been studied extensively. The enamino ketone (162) has been shown to react with phenyl isothiocyanate to give 163, the product of C acylation 114). Enamino ester derivatives of acetoacetic ester react similarly with isothiocyanates, also giving the C-acylated products 115). 

Amino esters (26) have also been shown to yield pyrido[2,3- Z]-pyrimidin-4(3I/)-ones (25, 27) when treated with isocyanates and isothiocyanates. The reactions proceed via intermediate ureido and thioureido derivatives. 

Cyclic a-methoxynitrones (225f) and (223 g) react respectively with isocyanates and isothiocyanates at ambient temperature, giving 1,3-dipolar cycloaddition products (763) and (764) (Scheme 2.314). Under similar conditions, the reaction of aldonitrone (223a) proceeds much more slowly to give cycloadducts... 

The reaction of isocyanates and isothiocyanates with 3(5)-aminopyrazole-4-carbonitrile affords aminopyrazolo[3,4-d]pyrimidines <90CCC728,91TL6787). Intermediate pyrazolyl thioureas were isolated in several cases and cyclized into aminopyrazolo[3,4-. The reaction of the amines (315) with formamide gives aminopyrazolo[3,4-t/]pyrimidines <8lOPP379>. 

Reaction with isocyanates and isopropyl-sulfonyl-chloride, via the ura-cil-enamino esters, easily gives pyrimido[4,5-Thermal cyclization of 6-amino-uracil-5-thiocarboxamides, prepared by reacting 6-aminouracils with isothiocyanates yields pyrimido[4,5-[Pg.163]

Other zwitterionic 18-electron d°-anionic metallocene complexes 26-29 with one Zr-heteroelement cr-bond can be prepared following the same strategy. This implies the treatment of 16a with an equimolecular amount of heterocumulenes (C02, CS2, Cy-N=C=N-Cy, R-N=C=S, R-N=C=0) (Scheme 7) [29]. It is also reasonable to propose here that the formation of all these new systems is due first to a nucleophilic attack of the free phosphine of 16a at the electrophilic center of the organic substrate. In the second step, cyclization reaction on the coordi-natively unsaturated metal center occurs to form the stable pentavalent anionic zirconocene products. With isocyanates and isothiocyanates, the anionic charge... 

Reaction of (2,3-di-/er/-butylcycloprop-2-enylidene)(trimethylsilyl)phosphane with isocyanates and isothiocyanates yielded the imido esters 3 or the thioamides 4, respectively. 

The reactions of 2-aminobenzimidazoles have been reviewed <83S86l>. The compounds form Schiffs bases with carbonyl compounds, with isocyanates and isothiocyanates they give ureas and thioureas, they are subject to 1,3-dipolar addition reactions, and to the formation of carbamates on acylation and aroylation. When aminoimidazoles are acylated there is frequently competition between the annular and exocyclic nitrogen (see above). Add chlorides and anhydrides (soft) acylate the amino group chlorocarbonic acid esters (hard) are specific for the heteroatom <84CHE204>. When heated, the A -acyl products isomerize (Scheme 91). 

Catalytic activity. Diazoalkanes, in particular phenyldiazomethane. catalyze the condensation of active hydrogen compounds, for example methyl salicylate (1), with isocyanates and isothiocyanates. The primary adduct (2) undergoes cycliza-tion to (3). The rate of the catalyzed reaction parallels the proton mobility of the... 

Reaction of dihydro[l,2,4,5]tetrazine diester (27) with isocyanate and isothiocyanate resulted in formation of the bis adduct (28) in most cases (Equation (2)). With isothiocyanates (X = S), the bicycle (29) was also formed <92S879>. 

The reaction of aminosugar 704 with isocyanates and isothiocyanates has been studied extensively (85AQ(C)147 91M12, 91M13). The reaction gave 703 via the formation of a ureido derivative, which is too reactive to be isolated. The formation of 705 from 704 during the acetylation and deacetylation was studied. 

Gas-phase reactions of acylium and thioacylium ions with isocyanate and isothiocyanate were investigated by MS <2005JAM1602>. The use of liquid chromatography/mass spectrometry (LC/MS) for the confirmation and quantification of thiomethoxam has been reported <2005ANA21>. 

Related reactions of thiolate anions with ort/zo-chloromethyl-phenyl(diphenyl)phosphine have provided a range of ort/ o-alkyl and aryl-thiomethylphenyl(diphenyl)phosphines. " The reactions of 2-amino-alkylphosphines with isocyanates and isothiocyanates have provided routes to new chiral phosphinoalkyl-urea and -thiourea ligands. Similarly, treatment of hydroxy- or amino-functional arylphosphines with isocyanides in the presence of a cyclooctadienepalladium(II) complex results in the formation of bidentate arylphosphino-carbene palladium complexes. New chiral phosphinoarylphosphoramidite ligands, e.g.,... 

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