Imidoyl isothiocyanates

Imidoyl isothiocyanates 74 are readily available through stepwise nucleophilic substitution of iV-phenyl(phenyl-imino)methylchloromethanimidoyl chloride with secondary amines and potassium thiocyanate. Subsequent thermal intramolecular cyclization of intermediates 74 affords substituted 1,3,5-benzotriazocine derivatives 75 (Equation 8 <2005ARK96>). 

From Imidoyl Isocyanates, Imidoyl Isothiocyanates, or Imidoylcarbodiimides... 

Cyclocondensation of substituted isothiocyanates 24 with amidines, isoureas, isothioureas or guanidines provides 1,3,5-triazine-2(1 //j-thiones 25 in good yield.433 43s Generally, aroyl isothiocyanates and imidoyl isothiocyanates are employed. 

The incorporation of the 1,3-diaza-1,3-butadiene system into a reactive heterocumulene system, imidoyl isothiocyanates and imidoyl isocyanates [Eq. (54)],l30 137... 

A heterogeneous mixture of N-isopropyl-2-oxopropionimidoyl chloride, mercuric thiocyanate, and CCI4 shaken 5 hrs. at room temp. -> N-isopropyl-2-oxopropion-imidoyl isothiocyanate. Y 76%. F. e., also with NaSCN in acetone as homogeneous medium, s. J. Goerdeler, F. M. Panshiri, and W. Vollrath, B. 108, 3071 (1975). 

A-Phenylimidoyl isocyanates and JV-phenylbenzimidoyl isothiocyanates 8 which are easily available from the corresponding imidoyl chlorides and potassium cyanate or potassi-... 

Cycloaddition of a,3-unsaturated ketones, acyl ketenes, acyl, thioacyl, imidoyl and vinyl isocyanates, as well as the corresponding isothiocyanates, to the C=C bond of vinylidenephosphoranes leads to the formation of six-membered heterocycles carrying an exocyclic ylide function e.g. equation 117). In some instances the mentioned thioisocyanates, however, may undergo [2 + 2] cycloaddition at the C=S bond. Interestingly N-aryliminovinylidenetriphenylphosphoranes dimerize in a [4 2] cycloaddition on heating alone. 

Cyclic derivatives have also been prepared from quinoxaline-2,3-dithiones by reaction with phosgene (COClj), thiophosgene (CSCI2), and thionyl chloride (SOCI2). 2,3-Disubstituted quinoxalines result from the reaction of the dithiones with isocyanates, isothiocyanates, and imidoyl chlorides (e.g., PhCCl=NMe). Derivatives of quinoxaline-2,3-dithiones incorporating arsenic, antimony, and tin have been prepared for example, with BujSnCl the 2,3-disubstituted quinoxaline 22 is obtained, and... 

However, this behavior is not completely general, since fragmentation of likewise substituted imidoyls 5 can follow two competitive pathways depending on the stability of the released radical (R or Y). For instance, addition of methylsulfanyl radicals to tcrt-butyl isonitrile does not afford tert-butyl isothiocyanate (6, R = tert-Bu, X = S) but instead methyl thiocyanate (7, XY = SMe), due to preferential formation of the more stable tert-huiyl radical [5f]. 

Fragmentation of imidoyl radical 34 to isothiocyanate was sometimes a competing process, especially when R H and the scission yields a fairly stable radical e.g., R = CH2C02Me) in those cases, control over the two competing reactions was gained by adequate temperature adjustment. 

It is worth noting that the same kind of reactions can be carried out by tin-radical-mediated ring closure of analogous isothiocyanates e.g., 33, 37, 39, NC = NCS) [22b,c], In this case, the intermediate a-thio-substituted imidoyl radical is generated by addition of a stannyl radical to the sulfur atom of the isothiocyanate. Although it had been known for a few decades, this way to imidoyl radicals had found very little application in organic synthesis. Bachi s work was the first example of synthesis of heterocyclic compounds by radical addition to isothiocyanates, showing the way to further possible applications [9]. 

Benati L, Calestani G, Leardini R, Minozzi M, Naimi D, Spagnolo P, Strazzari S, Zanardi G (2003) Cascade radical reactions via a-(arylsulfanyl)imidoyl radicals competitive [4-1-2] and [4+1] radical annulations of alkynyl isothiocyanates with aryl radicals. J Org Chem 68 3454-3464... 

The mechanism of the chlorination of isothiocyanates involves initial addition of one mole of chlorine to the C=S bond to produce the l-(chloro-thio)formimidoyl chlorides XIX (26.56a,95imidoyl chlorides and demonstrated that addition of a second mole of chlorine converts the intermediate XIX to the carbonimidoyl dichloride. 

However, the reaction proceeds preferentially via route (a), as evidenced by the isolation of 72 % of the tetrameric cyanogen chloride XXXVIII. The triazine derivative XXXVIII can also be obtained by chlorination of the corresponding isothiocyanate C% A somewhat lower yield of the triazinyl-bis-carbonimidoyl chloride was obtained in the chlorination of 2,6-bis(di-methylamino)-4-chloro-l,3,5-triazine ( ). If cyclic carbamoyl chlorides, or carbamoyl chlorides having alkyl substituents other than methyl are chlorinated, the expected imidoyl chlorides are obtained For... 

For example, Dimroth treated thioamides, derived from isothiocyanates and malonates, with phosphorus pentachloride, and he obtained the corresponding imidoyl chlorides (III), which can be dehydro-chlorinated to produce the ketenimines IV. 

In addition to azomethines and oximes, various heterocumulenes, such as ketenimines, isocyanates and isothiocyanates, can be used to synthesize imidoyl chlorides. For example, addition of chlorine to ketenimines LXIX affords a-chloroimidoyl chlorides LXX... 

The addition of hydrocyanic acid to isothiocyanates yields the 1 1 adducts LXXIV, which on subsequent chlorination afford the imidoyl chlorides LXXV ( ). 

Carbon disulfide and isothiocyanates have also proven suitable electrophiles for the preparation of thiazoles via the Schollkopf reaction. Isocyanides bearing electron-withdrawing a-substituents are insufficiently nucleophilic to react with nitriles to afford the eorresponding imidazoles, however iV-alkyl 4-tosylimidazoles are accessible through the sodium hydride-mediated condensation of toluenesulfonylmethyl isocyanide and imidoyl chlorides. Furthermore, the more electron-rich -tolylthiomethyl isocyanide reacts smoothly with carbodiimides and nitriles to afford the corresponding imidazoles. ... 

Several reactive isothiocyanates undergo dimerization reactions in which one of the isothiocyanates functions as the diene and the other isothiocyanate reacts as the dienophile. These [4-1-2] cycloaddition reactions are very pronounced with heterocyclic isothiocyanates and isothiocyanates having carbonyl, thiocarbonyl and imidoyl substituents. For example, 2-pyridyl isothiocyanate undergoes dimerization to give the triazine derivative 2. ... 

Imidoyl -, thiocarbamoyl - and ethylmercaptothiocarbonyl isothiocyanatesalso afford dimers formed in a [4-1-2]] cycloaddition reaction. Carbamoyl isothiocyanates are in equilibrium with thiocarbamoyl isocyanates therefore on standing mixed dimers 3 of the... 

The dimerization of carbonyl-, thiocarbonyl-, imidoyl- and thiocarbamoyl isothiocyanates proceeds in a [4-1-2] cycloaddition reaction (see Section 3.3.2.2). Carbonyl isothiocyanates also readily undergo [4-1-2] cycloaddition reactions with aliphatic and aromatic azomethines, the former being considerably more reactive. For example, phenylcar-bonyl isothiocyanate reacts with benzylidenemethylamine 184 to give a [4-1-2] cycloadduct 185... 

Thiocarbamoyl- and imidoyl isothiocyanatesreact with phenyl isothiocyanate and carbodiimides to give the [4+2] cycloadducts. 

Likewise, imidoyl ketenimines 153 react as 1-aza-1,3-dienes in [4-1-2] cycloaddition reactions with phenyl isocyanate to give the cycloadducts 154 (62-67 % yields) or with tosyl isothiocyanate to give the cycloadducts 155 (62-69 % yields) . ... 

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