Isothiocyanates, reaction with

Azaindolizine, 5-chloro-nucleophilic substitution, 4, 458 8-Azaindolizine, 7-chloro-nucleophilic substitution, 4, 458 Azaindolizines basicity, 4, 454 electronic spectra, 4, 445 electrophilic substitution, 4, 453 halogenation, 4, 457 hydrogen/deuterium exchange, 4, 458 NMR, 4, 447, 449 nucleophilic attack, 4, 458 protonation, 4, 453 reaction with isothiocyanates, 4, 513 reactions, 5, 267 reviews, 4, 444 UV spectra, 4, 446, 449 Azaindolizines, amino-tautomerism, 4, 452... 

Amidines and cyclic amidines are also converted into 1,2,4-thiadiazoles by reaction with isothiocyanates, imino-sulfenyl chlorides, di- and trichloromethyl sulfenyl chlorides, and carbon disulfide in the presence of sulfur. Ureas, thioureas, guanidines, carbodiimides, and cyanimides react with chlorocarbonylsulfenyl chloride to produce 1,2,4-thiadiazol-5-one derivatives in another example of a type B synthesis <1996CHEC-II(4)307>. 

An important prerequisite in these reactions is the nucleophilicity of the imine nitrogen. Indeed, electron-withdrawing substituents in the aryl ring of (159) retard the reaction with isothiocyanates, whereas such substituents in the R group of the isothiocyanates enhance the reaction. No reaction occurs under the above chosen conditions (reflux in chloroform), when the aryl ring of (159) is replaced by a sulfonyl group <88BSB83>. 

Oxathiazolidin-3-imine (93) possesses a thioimidate moiety similar to 4-methyl-5-phenyl-imino-l,2,3,4-thiatriazoline (70) and is capable of undergoing cycloaddition-elimination reactions with isothiocyanates to give identical products, however at a much higher rate. Acetone can therefore be used as solvent to catalyze this kind of reaction of thiatriazolines. 

Organolithium reagents reaction with imidothioesters 114 reaction with isothiocyanates 42 reaction with non enethiolizable dithioesters 98 Orthotrithioesters 79 cleavage of 79 reaction with ketones 137 Oxathiane Eliel reagent 19 Oxaziridines as oxidising reagents 27 Oxiranes... 

The reaction of cyclohexylidenemalononitrile with CS2 under phase transfer conditions gives a 5,6,7,8-tetrahy-droisothiochroman-l-thione. Under the same conditions, reaction with isothiocyanates produces the corresponding 1-imine, but tetrahydroisoquinoline thiones and/or ketones are also formed, often in the major quantities, and this detracts from the synthesis (Scheme 187) <2000JHC1233>. 

Azirines, reaction with isothiocyanates, 15 Azo dye, 156-168. See also Dyes Azothiazoles, 105, 153, 170, 271-274 analytical applications, 107 by diazo coupling, 105 dyes, 107 IR spectra of, 107... 

Aminodithioles, available by a number of methods <66JPR(3l)2l4,64AJC447), undergo typical reactions including acylation, nitrosation and reaction with isothiocyanates <65LA(68l)l78, 65AJC61). 

The reaction between alkyl azides and isothiocyanates produces an isolable thiatriazoline (205 Scheme 43), which was thought to lose N2 on thermolysis to give an unstable intermediate (206), since this has apparently been trapped by a number of C=S containing compounds to give 1,2,4-dithiazolidine derivatives (76JHC883). Further reaction with isothiocyanate, however, occurred in three different ways, and depended on the nature of R3NCS, and on the reaction conditions. For ArNCS, the relative amounts of products (207),... 

A wider range of possibilities of preparing cyclic derivatives is offered by the presence of carboxyl and a-amino groups in the molecule. Substituted 5-oxazolinone (Scheme 4.23) is prepared by refluxing with TFA anhydride, and substituted 5-oxazolidinone (Scheme 4.24)by reaction with (halogenated) acetone [117,118]. Thiohydantoins are formed by reaction with isothiocyanate (Scheme 4.25). If R is methyl or phenyl, then the corresponding methyl- or phenylthiohydantoin is produced. Thiohydantoins are usually not volatile enough and for the purposes of GC analyses must be further modified, e.g., by trimethylsilylation [119,120]. 

Several early examples of reactions with isothiocyanates have been tabulated [A] the following more recent example has also been carried out by a one pot procedure [13] ... 

Figure 10 Schematic representation of the most common reactions for labeling an amine (a) reaction with isothiocyanate to give a thiourea (b) reaction with a Succinimidil ester to give an amide (c) reaction with a sulfonyl chloride to give a sulfonamide (d) reaction with an aldehyde to give an imine (Schiff s base) and (e) reaction with a carbodiimide-activated carboxylic acid to give an amide.

Acrylates can also be used in Michael addition with primary amine and, after further reaction with isothiocyanate, supported thioureas are isolated. These can then undergo a cleavage under basic conditions leading to cyclisation and formation of tetrahydrothioxopyrimidinones [129], Onium salts supported isothiocyanates can also be used with this methodology and lead to the formation of various guanidines [130] (Fig. 41). 

Aminothienopyrimidinones 41 were synthesized by cyclization of vic-cyanothienylureas 42 generated in situ by the reaction of 2-amino-3-cyanothiophenes 30 with isothiocyanates (1985CB4473) or urea (1990MI1). Compound 41 with R3 = H exists predominantly as the tautomeric 4-NH form. The reactions with isothiocyanates are accompanied by dimerization as a side process (1991JPR229). 

The parent 2-imino-l,3-dioxolane (29 R = H) was first prepared by reaction of the Af-chloro analogue with NaNH2 in liquid ammonia <74JOC3442> and the formation of A -substituted analogues is best achieved from the tin compound (300) and an isothiocyanate as described in Section 3.10.8.2. The sulfur analogue (310) similarly gives good yields of the 2-imino-1,3-oxathiolanes by reaction with isothiocyanates and of l,3-oxathiolane-2-thione (42) with CS2. An early but efficient preparation of... 

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