4- -5-methylpyridin methanol, water

Figure 2-15. Retention of alkylpyridines on Phenomenex Luna-C18 column from methanol/water eluent, (diamonds, pyridine squares, 4-methylpyridine triangles, 4-ethylpyridine).

In rather unreliable reactions, pyridine and its 3-methyl and 3,5-dimethyl derivatives with MP and 1 mole of methanol yield 2-methoxy-1,2-dihydropyridines (e.g., 122).292 This contrasts with DMAD which yields indolizines (e.g., 35 and 36), perhaps because the extra ester group encourages the methoxide ion to add to the exocyclic double bond, but 4-methylpyridine with MP gives the same products (see earlier) as obtained in the absence of added methanol.292 Replacing the methanol by water gave compounds exemplified by 123, where the 5 6 -double... 

Figure 1. Correlation of a semiempirieal polarity scale based on the shift of the solvatoehromie band of the compound SB with the Dimroth parameter, Exso (D Water, (2) methanol, (3) ethanol, (4) 1-propanol, (5) 2-propanol, (6) 1-butanol, (7) 2-methyl-2-propanol, (8) DMFA, (9) DMSO, (10) pyridine, (11) benzylaleohol, (12) acetonitrile, (14) acetone, (16) dioxane, (17) THF, (19) 2-methylpyridine, (22) formamide. vcm", and ET30and E-p(SB) (kcal/mol).

---