Triazines production

The reaction sequence starts from tetrazolyldiazonium salt 42 prepared from aminotetrazole 41 by diazotation. This compound when reacted with arylformylacetonitrile 43 leads to the intermediate formation of the condensation product 44, which easily undergoes ring closure to 45. This tetrazolo[5,l-z][l,2,4]triazine compound, however, forms an equilibrium with the valence bond isomeric azide 46, which can participate in a different ring closure than the reverse route, and yields the tetrazolo[l,5-A][l,2,4]triazine product 47. The reaction was carried out with a series of various aryl derivatives and proceeded in good to excellent yields (68-87%). 

The H+ and NH forms of homoionic montmorillonite promote the hydrolysis of chloro-s-triazines to the hydroxy analogs (hydroxy-s-triazines) (73). Apparently, the surface acidity of these clays was extremely high, since no degradation was observed in control experiments conducted at pH 3.5 in homogeneous aqueous solution. Russell et al. (73) suggested that the hydroxy-s-triazine products were stabilized in the protonated form at the silicate surface. The IR spectra of these surface complexes agreed with the spectra obtained in 6N HC1, and it was inferred that the pH at the clay surface was 3 to 4 units lower than that measured in suspension. 

R1 Reactants R2 R3 Triazine products Conditions A (% yield) + By-products Solvent Time (h) R R2 R3 (% yield)... 

In 1969 the reaction of 1,2,4,5-tetrazines (39) with imidates (198) was reported. The formation of the 1,2,4-triazine products (199) is explained by a [4 + 2] cycloaddition of the tetrazine with the C=N double bond of the imidate to give the bicyclic intermediate (200) which eliminates nitrogen and alcohol (69JHC497). Further studies on this reaction seem to... 

When 2-phenyl-l,3,5-triazine (8) is aminated with potassium amide in liquid ammonia at - 33 C a very slow Chichibabin reaction occurs, partly via the Sn(ANRORC) mechanism and partly via the SNAE process (ratio ca. 55 45). H NMR and l5N-labelling studies have demonstrated that in solution an equilibrium exists between the starting triazine, amine adducts, open-chain amidines and triazine product 9.53... 

A new synthesis of 6-arylamino-2-heteroarylimino-l,2-dihydro-l,3,5-triazines from 2,4-bis-(heteroarylimino)-l,3-diazetidines and amidines has been developed by Molina et al. The formation of the triazines was explained as an initial addition of the imino nitrogen of the amidine to the exocyclic C=N bond, followed by formation of an open chain intermediate. This intermediate cyclized, followed by elimination of 4-amino-6-methyl-3-methylthio-l,2,4-triazin-5(47/)-one to give the triazine product (Scheme 62) <87S150>. 1,3,5-Triazines (207) and (208) have been prepared from 2-acylimino-l,3-thiazetidines (204) by treatment with iso thioureas or guanidines respectively (Scheme 63) <91JHC177>. 

Tris(dimethylamino)-l,3,5-oxadiazinium chloride (223) was obtained when dimethyl-cyanamide and dimethylcarbamoyl chloride were heated together at 170°C for 20 min. When the salt (223) was heated with concentrated ammonia the l,3,5-triazin-2-one (224 R = H) was the product. The suggested mechanism follows the ANRORC pathway. The triazine product (224) can also be prepared more simply by hydrolysis of 2-chloro-4,6-bis(dimethylamino)-l,3,5-triazine by IM hydrochloric acid at boiling point for 3 h (Scheme 69) <85JCS(P1)1533> and 2-chloro-4,6-bis(dimethylamino)-l,3,5-triazine is available from cyanuric chloride and dimethylamine. The salt... 

It should be noted, however, that the lack of electron density in the 7t-system may be bypassed by creating local (T-electron density by lithiation and reaction with suitable electrophiles. Quenching of lithiated alkoxy-l,2,3-triazines with aromatic aldehydes generates (a-hydroxybenzyl)-l,2,3-triazines, products of an electrophilic attack on carbon. Dehydrogenation of their alcohol function with manganese dioxide affords formal Friedel-Crafts acylation products <1998MI119>. Lithiation has been discussed from a theoretical point of view in Section 9.01.2.13, and practical implications are presented in Section 9.01.5.5. 

Utilizing the method of Mamalis, bromides 106 could be converted directly to the desired triazine products 108 by alkylation of an iV-hydroxytriazine 107 (Equation 12) <2001JME3925>. 

The 3,5-diaryl-l,2,4,6-thiatriazine 1-oxides 47 were converted to the 1-chloro derivatives 140 with sulfuryl chloride (Scheme 18). Treatment of 47 with MCPBA gave the unexpected 1,3,5-triazine product 141 and an unknown byproduct (m.p. >300°C) (Scheme 18). No 1,2,4,6-thiatriazine 1,1-dioxides were isolated. A mechanism for formation of 141 was proposed <2000T7153>. 

Since the absorbent and waste products are liquids, the process can be operated in either a batch or continuous mode. Data from treating trials at two plants are given in Table 16-4. Case A was operated as a batch process using a conventional bubble tower. Case B was a continuous operation with the triazine injected into the gas ahead of a converted iron sponge tower. In both cases, complete hydrogen sulfide removal was observed. Triazine product consumption ranged from 0.04 to 0.06 gal/MMscf per ppm of H2S in the feed gas. 

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