Alkyl isothiocyanates, synthesis from

In the area of spironucleoside chemistry, a considerable effort has been devoted to the synthesis of 2-thiohydantocidin, its 5-epimer [154,155,166,167, 172] and other thiohydantoin spironucleosides [154,160,162,173,174], Thus, Puentes and co-workers have prepared recently [154,155] 2-thiohydantoin spironucleosides 164glycosyl isothiocyanates 162 via the transient thioureas 163, as depicted in Scheme 35. Aminoesters 161 and isothiocyanates 162 were obtained from psicofuranose spiroacetal 148 as well as from fruc-topyranose spiroacetal 156. 

Glutaconaldehyde anion serves as an interesting intermediate for the synthesis of heterocyclic compounds. The parent pyrylium perchlorate has been prepared from glutaconaldehyde and 70% perchloric acid in ether at -55°.° The reaction of glutaconaldehyde anion with alkyl and aryl isothiocyanates and... 

The thiophene synthesis described herein is related to the synthesis in solution reported by Laliberte, and Medawar4 but differs in some aspects from the procedure in homogeneous phase. Laliberte and Medawar succeeded in obtaining aminothio-phenes in a one-pot reaction from acceptor-substituted acetonitriles, isothiocyanates, a-haloketones, and sodium ethoxide. In contrast to their procedure, solid-phase S-alkylation of the intermediate thioamides under basic conditions led to the formation of product mixtures. We obtained pure aminothio-phenes only when conducting the S-alkylation under neutral or slightly acidic conditions. 

Diazo(trimethylsilyl)methyl lithium (3) was found to be the reagent of choice for the synthesis of azoles from heterocumulenes (Scheme 8.43). The reaction is typically carried out in ether at 0-20 °C. Thus, alkyl- (or aryl-)substituted keteni-mines are transformed into 1,2,3-triazoles 188 (246), while C-acceptor-substituted ketenimines yield either 4-aminopyrazoles 189 or 1,2,3-triazoles, depending on the substituents (247). Isocyanates are converted into 5-hydroxy-1,2,3-triazoles 190 (248). Reaction of 3 with isothiocyanates are strongly solvent dependent. 

A one-step procedure for the synthesis of 5-arylimino-l,2,4-thiadiazolin-3-ones (273) from a mixture of alkyl azide, substituted phenyl isothiocyanate and aryl or alkyl isocyanate has been reported (76AG(E)489). Evidence was presented to support the proposal that a... 

Only one synthesis leads to 2 alkyl-4-nitroisothiazolium salts (68) from open-chain precursors. Condensation of nitroketeneaminals with isothiocyanates followed by N—S bond formation using bromine leads to the isothiazoles 68 (20-25%) (Scheme 14).60... 

The reagents used for the completion of the purine heterocycle are essentially the same as those used for the Traubc synthesis. The purine ring is formed by condensation with derivatives of formic acid or other carboxylic acids. Alternatively, formylation of the amino group is accomplished by a mixture of formic acid and acetic anhydride followed by cyclization. Alkyl esters or trialkyl ortho esters are also versatile synthons for ring closure. Moreover, heating in formamide or cyclization with urea or thiourea provides a satisfactory route. Condensations with isothiocyanates show unusual versatility leading to 2-sulfanylpurin-6-ols. From carbonic acid derivatives, cyclization is reported with chlorocarbonic esters, diethyl carbonate or carbon disulfide. 

N3-Substituted hydantoins and 2-thiohydantoins (9) are prepared by acid-catalyzed cyclization of the substituted ureido or thioureido acids (8) obtained from a reaction of a-amino acids with alkyl or aryl isocyanates and isothiocyanates.1 3,12 This method has been applied to prepare 2-selenohy-dantoins,13 and also in the stereospecific synthesis of (S)-(+)-l,5-cyclotrimethylene-3-phenyl-2-thiohydantoin.14... 

In primary synthesis 2-perimidinamines (660) can be prepared from the naphthalene diamine with bromocyanogen or cyanamide (Scheme 106). 2-Anilino derivatives have been obtained in reactions with aryl isothiocyanates. 2-iV,7V-Dimethylamino derivatives (662) have been obtained via the alkylated amine (661) using dimethylamino(trichloro)methane. Nucleophilic substitution by amine readily occurs in the 2-position when carrying a halo, sulfenyl, or sulfonyl substituent <81RCR816>. 

Drach and co-workers described a general synthesis of 2-alkyl(aryl)-5-hydrazino-4-phosphorylated-oxazoles 1640 from 1639 or 1641 (Scheme 1.421). Reactions of 1640 analogs with p-tolualdehyde, p-toluic chloride, and phenyl isothiocyanate gave the expected products. 

A general method of synthesis of carbonimidoyl difluorides from alkyl and aryl isothiocyanates was recently described by Sheppard Thus, upon reaction of isothiocyanates with mercuric fluoride, the corresponding carbonimidoyl difluorides were obtained in good yield. The reaction may... 

Scheme 39 Three component synthesis of 5-imino-l,2,4-thiadiazolidine-3-ones 199 from alkyl azides 195, allqd or ar)4 isocyanates 196 and ar)4 isothiocyanates 197 [ 142]...

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