Azidothiazoles

An interesting ring-chain tautomerism between 2-azidothiazole (328) and thiazolotetrazole (328a) has been reported (597, 618, 619), the 328 structure predominating (Scheme 190). The solvent polarity and basicity influences this equilibrium constant significantly (1592). 

A study of the relative stability of tra 5-2-azidothiazole 32b with respect to the corresponding cis conformer 32a showed that 32b is destabilized in the gas phase but appears to be the more stable conformer in solution (Scheme 23). The stability increases with increasing polarity of the solvent [98JA4723]. 

Heating 4-azidothiazoles having an imino or aldehyde group at the 5-position affords fused pyrazolo- and isoxazolo[3,4-d]thiazoles (Equation (7)). When an alkenyl group is in 5-position of the triazole ring, 4//-pyrrolo[2,3-[Pg.454]

The aminolysis of turns-1,2-bis(ethylsulfonyl)-1.2-dichlorocthcnc (336) by primary and secondary aliphatic amines in acetonitrile has been studied.305 Thermolysis in p-xylene solution of 4-azidothiazoles (337) displayed some interesting neighbouring-group effects,306 e.g. in (337) with R1 = Ph, R2 = (acceleration produced in parentheses) NO2 (19-fold), phenyliminomethyl (16-fold), formyl (4.5-fold), and acetyl (2.2-fold). Rate data for nucleophilic attack on phenyldimethylsulfonimn ions by... 

Arylsulfonylbenzimidoyl chlorides, with aminothiazoles, 50 Arylsulfonyl halides, 98, 115 Azide, with azothiazoles, 111 to carbamate, 16 Curtius rearrangement of, 15, 16 See also Sodium azide Azido thiazoles, 113 azidothiazole-thiazolotetrazole, 113 reactions of, 113... 

Phenyl lithium. 429 Phenylmagnesium bromide, 428 with 2-azidothiazoles, 113 Phosphate, chlorodiethyl, 401 chlorodiethylthio, 401 Phosphoric acid, diazotization with, 66 Phosphorous compounds, with 2-aminothia-zoles, 68, 69... 

Whereas in the gas phase and in nonpolar solvents sueh as tetraehloromethane and benzene, the 2-azidothiazole (38a) is the more stable isomer, in polar solvents such as dimethyl sulfoxide and hexamethylphosphorie triamide the bieyelie valenee isomer (38b) is the dominant speeies [100]. This result is in line with the faet that the dipole moment of phenyl azide g = 5.2 10 Cm) is smaller than that of cyclie 1,2,3-benzotriazole (// = 13.7 10 Cm). Similar results have been obtained for the valenee isomers of 3-azidopyrazine-l-oxide [204]. 

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