BASE-CATALYZED REACTIONS .34. ALKALI METAL CATALYZED SIDE-CHAIN ARALKYLATION OF 2-ALKYLPYRIDINES AND 4-ALKYLPYRIDINES WITH STYRENE, ALPHA-METHYLSTYRENE, AND CIS- AND TRANS-BETA-METHYLSTYRENE

The sodium- and potassium-catalyzed side-chain aralkylation reactions of 2- and 4-alkylpyridines with styrene, α-methylstyrene, and cis- and trons-β-methylstyrene were performed using the alkylpyridines in a 5:1 molar excess. For the most part, the reactions proceed readily at 0-25° to yield monoaddition products via a Michael-type addition mechanism, as well as di- and triaddition products in some cases. As the length and branching of the alkylpyridine are increased, the yields of the higher adducts decrease. The yields of the higher adducts, as well as the relative rates of reaction, also decrease as the steric hindrance of the reacting olefin increases on going from styrene to α-methylstyrene to β-methylstyrene. 4-Alkylpyridines react more readily than 2-alkylpyridines. Also formed, in some cases, are diaddition products resulting from a chain-lengthening process. With 2- and 4-picoline and 2- and 4-ethylpyridine, trans-β-methylstyrene reacts faster than cis, due to the greater conjugation of the trans olefin. With 4-isopropylpyridine, however, the results are reversed. © 1969, American Chemical Society. All rights reserved.