Alkylimino group

Isothiocyanate oxide hydrobromides,164 however, all show the characteristic absorption in the imino region their cyclic disulfide structure (153) is thus indicated, presupposing the isomerization 153— 152 (R = alkyl) on liberation of the free base. When a rearrangement of this type can occur readily, it seems reasonable that the dithiazolidine form (153), incorporating the basic alkylimino group, would be the more stable in the presence of acid. 

Iminohydantoins have been prepared according to Scheme 7.133,134 The hydrolysis of the alkylimino groups affords hydantoins and 2-thiohydantoins. 

Disubstituted 5-imino-l,2,4-dithiazolidine-3-thiones (317) with a 5-alkylimino group rearranged when boiled in triethylamine in the presence of ethanol to give 318 (91JPR107) (Scheme 98). 

When 1,2,4-trimethylthiosemicarbazide is allowed to react with 2-bromo-l,2-diphenylethan-l-one under analogous conditions, a 4//-l,3,4-thiadiazine is not obtained.45 Microanalytical as well as mass and IR spectroscopic data indicate the existence of a product with structure A. 4-Isopropyl- and 4-terf-butyl-l, 2-dimethylthiosemicarbazides react analogously. Worthy of note is the fact that hydrolysis of the alkylimino group occurs readily under the condensation conditions, especially since reactions of this type are not observed for jV-alkyl-3-alkyl-67/-1,3,4-thiadiazin-2(3//)-imines. Even by varying the reaction conditions, an (V,3,4-trimethyl-5,6-diphenyl-6//-l,3,4-thiadiazin-2(3//)-imine could not be isolated. 

Most 4-amido-3-pyrazolin-5-ones have been prepared either by acylation of secondary amines537 618,1471 (4-alkylimino-3-pyrazol-idinones) or by acylation of the primary amine1471 followed by alkylation.537 Shimidzu1297 has reported the replacement of a methyl group by a cyano group and conversion of this to a thiourea (eq. 198). 

---