Lutidine, halogenation

Mono-substitution occurs most readily in the stepwise replacement of the halogen substituents of 2,4,6-trichloro-s-triazine with aqueous methanol and sodium bicarbonate (30°, 30 min), the monomethoxy derivative (324) is obtained on heating (65°, 30 min), the disubstitu-ted derivative is formed and on brief heating (65°) with the more basic sodium carbonate or methanolic sodium hydroxide (25°, 3 hr) complete methoxylation (320) occurs. Ethanolic ethoxide (25°, 1 hr) or sodium carbonate (35°) is sufficient to give complete ethoxy-dechlorination. The corresponding phenoxy derivatives are obtained on treatment with one (0°), two (15°, 1 hr), or three equivalents (25-70°, 3 hr) of various sodium phenoxides in aqueous acetone. The stepwise reaction with phenols, alcohols, or thiols proceeds in better yield in organic solvents (acetone or chloroform) with collidine or 2,6-lutidine as acid acceptors than in aqueous sodium bicarbonate. ... 

Besides the effect of solvent polarity, the C=C rotation in many push-pull ethylenes is sensitive to acid catalysis (143). This is probably explained by protonation of the acceptor groups, for example, the oxygen atoms in C=0 groups (16), which increases their acceptor capacity. Small amounts of acids in halogenated solvents, or acidic impurities, may have drastic effects on the barriers, and it is advisable to add a small quantity of a base such as 2,4-lutidine to obtain reliable rate constants (81). Basic catalysis is also possible, but it has only been observed in compounds containing secondary amino groups (38). 

An increase in susceptibility to nucleophilic substitution of halogen at all ring positions by an N-oxide function has been observed. Relative reactivities toward sodium methoxide have been reported for 4-chloropyridine, 4-chloro-2,6-luti-dine, 4-chloro-3-nitro-2,6-lutidine, and their A -oxides, and for 2-bromo-, 2-bromo-3-methyl- and 2-bromo-5-methylpyridine, and their A7-oxides. ... 

Popov Al, Rygg RH (1957) Studies on the chemistry of halogens and of polyhalides. XI. Molecular complexes of pyridine, 2-picoline and 2,6-lutidine with iodine and iodine halides. J Am Chem Soc 79 4622-4625... 

In a kinetic study of the halogenation of pyridine, quinoline, isoquinoline, 2-picoline, and 2,6-lutidine with ICl, linear Eyring plots are obtained. Dipole-moment calculations indicate that the charge-transfer state is the transition state. ... 

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