Acetic Anhydride → 3-Cyano-2-(4-methylphenyl)pyridine

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Reaction Steps

Synthetic Scheme XXV shows the 8-step preparation of the alkylating reagent 2-(4-bromomethylphenyl)-3-cyanopyridine (57) from 2-amino-3-picoline (58) (Aldrich). In step 1, the aminopicoline 58 was converted to the bromopicoline 59 by reaction with bromine, concentrated hydrobromic acid, and sodium nitrite at 0° C. In step 2, the picoline 59 was oxidized with KMNO4 to give the corresponding carboxylic acid 60. In step 3, the acid 60 was reduced to the alcohol 61 with borane/THF. In step 4, the alcohol 61 was oxidized to the aldelyde 62 under Swern conditions or by using MnO2. In step 5, the aldehyde 62 was reacted with hydroxylamine to give the oxime 63. In step 6, the oxime 63 was converted to 2-bromo-3-cyanopyridine (64) with acetic anhydride at reflux. In step 7, the nitrile 64 was coupled with 4-methylphenylboronic acid (56) (Scheme XXIV) using Snieckus conditions (Scheme XIII) to give 3-cyano-2-(4-methylphenyl)pyridine (65). In step 8, 65 was brominated with NBS/AIBN in carbon-tetrachloride at reflux to give the desired alkylating reagent 57. ##STR83##

Provenance & Evidence