Isothiocyanates with azirines

Alky]-5-imino-3-methy -A2-l,2,4-thiadiazoIines react exotherm ally at 0°C with dibenzoy] or dimethoxy carbonylacetylenes in tetrahydrofuran to give the 2-alkylaminothiazoles in high yields (1564). The cycio addition reaction of 2-pyridyl isothiocyanates with 1-azirines results in the formation of 2-pyridylaminothiazoles (1565). 

Isopropanol, with aminothiazoles, 47 Isothiocyanates, 58 with 2-aminobenzothiazoles, 59 with 2-aminothiazoles, 65 with azirines, 15... 

There are few examples of this type of synthesis. Typically, an azirine reacts with isocyanates or isothiocyanates to yield the triazine via a series of dipolar intermediates. The products may be contaminated with the isocyanate trimer the example of Scheme 114 below is typical. The novel spiro compound (188) is formed by a similar route (Scheme 115) (79HCA1429, 81LA264). 

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... 

In the reaction of 3-dialkylamino-2,2-dimethyl-2H-azirines 143 with isothiocyanates carbodiimides 144 are formed in high yields. The obtained carbodiimides are in equilibrium with a zwitterionic form 145. ... 

The reaction of azirines (114) with benzoyl isothiocyanate has been discussed in terms of a (2 + 2)-cycloaddition of the azirine with the carbon-sulfur double bond, followed by rearrangement to the 2-benzamidothiazole (116).IU Experimental evidence for the formation of the (2 + 2)-cycloadduct (115) has not been provided. Reactions of azirines with other heterocumulenes such as thiobenzoyl isocyanate and... 

Triphenyl-4,7-dihydro-l,3,5-thiadiazepin-4-one was prepared in 1974 by the reaction of thiobenzoyl isocyanate with 2,3-diphenyl-l-azirine <74JOC3763>. The second examples of this ring system, 1,3,5-thiadiazepin-6-ones (112), were prepared by the reaction of the isothiocyanate derivatives (110) with methanol or isopropylthiol. The initially formed adducts (111) were readily converted into the final products (112) upon treatment with a base, such as sodiiun methoxide (Scheme 18) <86S817>. 

An ethereal soln. of trimethylsilyl isocyanate added with stirring to a soln. of startg. azirine in ether, then after a few min methanol in ether added slowly - 4-(dimethylamino)-5,5-dimethyl-3-imidazolin-2-one. Y 78%. F.e., also 4-amino-A -2-imidazolinethiones with trimethylsilyl isothiocyanate, s. I. Handke, E. Schaumann, J. Org. Chem. 53, 5298-300 (1988). 

Photoreactions have also been observed between 3-phenyl-2/f-azirines and ketenes, carbodiimides, isocyanates as well as isothiocyanates. The isocyanates and their thio analogs react with the C-O and C-S double bonds, respectively, to give 79, 80, and 81, and not with the C-N double bond. ... 

Phenylcarbonyl isothiocyanate reacts with 1-azirines to give [2+2] cycloadducts 51 however, the strained bicyclic adduct undergoes rearrangement to give 4,5-disubstituted 2-benzamido-l,3-thiazoles 52". ... 

In the reaction of 3-(dialkylamino)-2//-azirines with isothiocyanates, a similar [2+2] cycloaddition across the C=N bond occurs however in this case the strained bicyclic adducts undergo further transformation to give carbodiimides 54 which are in equilibrium with the dipolar heterocycle 53. ... 

In the reaction of 3-(dialkylamino)-2//-azirines with trimethylsilyl isothiocyanate the initially formed [2+2] cycloadduct 59 again is transformed into the five-membered ring compound 60, which on treatment with methanol to remove the silyl group is converted into 4-(dialkylamino)imidazoline-2-thiones 61 (yield 26-80... 

Type B (C—C—N + C—S) Syntheses.—Benzoyl isothiocyanate reacts with 2,2-dimethyl-3-dimethylamino-2/f-azirine to give the interesting dipolar compound 4,4-dimethyl-A -thiazoline-5-dimethylimminium-2-benzocarboxamidate... 

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