Methyl groups 1,3,5-triazine

Both of these structures are open-chained compounds corresponding to crown ethers in function if not exactly in structure (see Chap. 7). They have repeating ethyleneoxy side-chains generally terminated in a methyl group. Montanari and co-workers introduced the polypodes 22 as phase transfer catalysts . These compounds were based on the triazine nucleus as illustrated below. The first octopus molecule (23) was prepared by Vogtle and Weber and is shown below. The implication of the name is that the compound is multiarmed and not specifically that it has eight such side-chains. Related molecules have recently been prepared by Hyatt and the name octopus adopted. For further information on this group of compounds and for examples of structures, refer to the discussion and tables in Chap. 7. 

The pyrimidine compounds are known to undergo a rearrangement of the 0-alkyl derivatives to the iV-alkyl ones. The methoxy derivatives of 1,3,5-triazine display a similar behavior. On applying methyl iodide to 2,4-dimethoxy-l,3,5-triazine one of the methyl groups is shifted giving rise to l-methyl-4-methoxy-derivative (22). This compound was also obtained by methylation of 4-methoxy-2-oxo-1,2-dihydro-1,3,5-triazine (18) with diazomethane. At higher temperature (100°C) in presence of methyl iodide a shift of both methyl groups takes place and methiodide is formed simultaneously (23). Similarly,... 

The highly 7r-deficient character of the 1,2,4-triazine ring increases the nucle-ophilicity of the methyl group in methyl-1,2,4-triazine A-oxides in reactions with electrophilic alkenes and aldehydes. Thus treatment of the 6-methyl-3-phenyl-1,2,4-triazine 4-oxide 113 with l-(dimethylamino)-l-ethoxyethylene leads to the... 

The reaction of 3-amino-1,2,4-triazine 1-oxide 1 with methyl iodide in the presence of sodium bicarbonate leads to the methylation of the amino group to afford 3-methylamino-l,2,4-tiiazine 1-oxide 123. This iV-oxide 123, under neutral conditions in the presence of Mel, undergoes methyl group migration to the N(2) atom of the 1,2,4-triazine ring, yielding 3-imino-2-methyl-1,2,4-triazine 1-oxide 124. The same product 124 was obtained by direct methylation of compound 1 under neutral conditions (84TL1677). 

A similar migration of the methyl group was found in 3-methoxy-l,2,4-triazine 2-oxides 18 under the same conditions to afford the 2-methoxy-1,2,4-triazin-3(2/f)-one 125 (84TL1677). 

In methyl-1,2,4-triazines (109) the 5-methyl groups shows rapid H-D exchange in basic media while the other methyl groups show very slow exchange (74UP21900). 

A methyl group in the 5-position can be oxidized by potassium permanganate to a carboxyl group, while one in the 3- or 6-position is converted into an oxo group under the same reaction conditions, leading to l,2,4-triazin-3- or -6-ones. Oxidation of 5,6-dimethyl-... 

The chemistry of the ring substituents remains largely unknown. Shaw et al. have shown that the methyl group has similar properties to those of an alkyl-1,3,5-triazine (81JHC75). The 4-cyano group may be removed by heating with polyphosphoric acid at 200 °C (73ACS3259). 

Triazine furnishes the species 31 when a solution in trifluoro-acetic acid is titrated with water. The new upheld signals thus produced in PMR spectra are not seen when the hydrogen atom on C-5 is replaced by a methyl group. The hydration is reversible by basification.53 Acidification of an aqueous solution of the anhydrous sodium salt of 3-hydroxy-l,2,4-triazine precipitated a hydrate of the neutral species, and elemental analysis combined with PMR (r5 4.62) indicated structure 32. This substance was not dehydrated during sublimation or heating in distilling toluene.54... 

A commonly observed phenomenon in proton NMR is the nonequivalence due to restricted rotation of the two methyl groups of an NMe2 substituent. 5-Dimethylamino-3-methylpyrim-ido[5,4-e]-1,2,4-triazine (49), a 7-azapteridine, displays this property and exhibits two methyl singlets in TFA and also in DMSO solution (5 4.30, 5 3.88, and S 3.7, S 3.3, respectively). The corresponding... 

The trichloromethyl group in s-triazines is sufficiently reactive to he displaced by ammonia, amines, or alkoxides even if two deactivating groups have already been introduced. In contrast, under much more vigorous conditions benzotrichloride and 2,6-bis(trichloro-methyl)pyridine are unreactive towards ammonia in dimethyl-formamide (2 hr, 165°). Tris-amination of 2,4,6-tris-(trichloro-methyl)-s-triazine is complete in aprotic, but not in protic, solvents. 

The heterocyclic ring in l,2,4-triazine-3,5-dione (12) and its 6-methyl derivative (13) is planar. The data clearly show that in the crystal only the dione structure is present no indication of any other tautomeric structure was found. The methyl group in the 6-position of (13) has an influence on the bond lengths of the two carbonyl groups. While in (12) the two carbonyl groups are equal (1.224 A), in (13) two different distances were found C(3)=0 = 1.213 A and C(5)=0 = 1.242 A. In the ribosides (14) and (15) both carbonyl groups are nearly the same length. 

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