Efficient method for a synthesis of N -substituted dithiazinanes via transamination of N -methyl-1,3,5-dithiazinane with arylamines and hydrazines

The efficient method for a synthesis of N -substituted dithiazinanes based on the transamination reaction of N -methyl-1,3,5-dithiazinane with arylamines and hydrazines in the presence of Sm and Co catalysts has been developed.


Introduction
3][24][25] Nevertheless, this method has definite limitation associated with the use of gaseous Н2S and aqueous solution of СН2О.As a rule, these reactions furnish a mixture of heterocyclic compounds.At the same time, the synthesis of N-substituted 1,3,5-dithiazinanes by thermal transamination of N-tertbutyl-1,3,5-dithiazinane with the aid of 1,3,5-trimethyltriazinane (68 o C, 3 h) has been also reported. 26

Scheme 1
The NMR experiments showed that the samarium ions are coordinated by the nitrogen atom of arylamine to form the intermediate complex.In the 1 H and 13 C NMR spectra of this complex the signals attributable to protons of the amino group and the carbon atom associated with the nitrogen atom, respectively, were shifted in a higher field as compared to those appeared in the spectra of initial arylamine.Probably, under reaction conditions, the N-H bond in original arylamine is activated due to the coordination of the lone electron pair of the nitrogen atom with the metal ion.As a result, transamination of N-methyl-1,3,5-dithiazinane occurs giving rise to thermodynamically more stable N-aryl-1,3,5-dithiazinane.
As reported, 28 the multicomponent condensation of o-, m-, and p-phenylenediamines with H2S and CH2O proceeds unambiguously giving rise to a mixture of heterocyclic compounds for o-isomer, and a mixture of macroheterocycles in the case of m-isomer.The thiomethylation reaction of p-phenylenediamine with the above reagents has failed.

Scheme 2
The positive results on catalytic cyclothiomethylation of arylamines providing formation of dithiazinanes 1-3 have encouraged us and gave hope for the successful implementation of Nmethyl-1,3,5-dithiazinane transamination with aryl hydrazine (Scheme 3).

Conclusions
In summary we have developed an efficient method for synthesizing a variety of N-substituted 1,3,5-ditiazinanes via catalytic transamination of N-methyl-1,3,5-ditiazinane with arylamines and arylhydrazines.Unique structure of N-substituted 1,3,5-ditiazinanes opens up new possibilities for using these classes of compounds as potential biologically active compounds, food additives, extractants and other valuable substances.

Experimental Section
General.Progress of the reaction was monitored by thin-layer chromatography (TLC) using Silufol W-254 plates and iodine vapor as a revealing agent.Analysis of the reaction products was performed by high performance liquid chromatography (HPLC) using Beckman Altex gradient liquid Chromatograph (model 330, U.S.A.) with UV detection at 340 nm.The one-dimensional ( 1 H, 13 C) and two dimensional homo-(COSY) and heteronuclear (HSQC, HMBC) NMR spectra were recorded in CDCl3 on a spectrometer Bruker Avance 400 [400.13MHz ( 1 H) and 100.62 MHz ( 13 C)] in accordance with a standard Bruker protocol.Infrared spectra (IR) spectra were recorded using a Specord IR-75 instrument in liquid paraffin and in KBr pellets.Chromato-mass spectrometric analysis of compounds was performed on a Finnigan 4021 instrument (glass capillary column 50000x0.25mm,stationary phase HP-5, helium as the carrier gas, temperature programming from 50 to 300 o C at a rate of 5 o C min -1 , evaporator temperature 280 °C, the temperature of the ion source 250 °C [EI, 70 eV]) and also using SHIMADZU QP-2010Plus instrument (Supelco PTE-5 capillary column 30m x 0.25mm).Elemental analysis of the samples was carried out using Carlo Erba Elemental Analyzer model 1106.The products were isolated by column chromatography on silica gel SiO2.Compounds 1a, 1b, 6 and 7 were identified by comparison with the known samples. 17,25