反应详情

Synthetic Scheme XXVII shows the 5-step preparation of the alkylating reagent 4-(4-bromomethylphenyl)-3-cyanopyridine (73) from 4-bromopyridine (74) (Aldrich). In step 1, the ortho-bromo carbanion was generated with LDA in THF at -78° C. and reacted with anhydrous DMF to give 4-bromo-3-carboxaldehyde 75. In step 2, the aldehyde 75 was reacted with hydroxylamine to give the oxime 76. In step 3, the oxime 76 was dehydrated with 1,1'-carbonyldiimidazole in methylene chloride at reflux to give 4-bromo-3-cyanopyridine (77). In step 4, the nitrile 77 was coupled with 4-methylphenylboronic acid (56) (Scheme XXIV) using Snieckus conditions (Scheme XIII) to give 3-cyano-4-(4-methylphenyl)pridine (78). In step 5, 78 was brominated with NBS/AIBN in carbon tetrachloride at reflux to give the desired alkylating reagent 73. ##STR90##