High-Yield Reactions to Introduce Aldehyde Groups into Pyridine Derivatives

摘要

The mechanism of the deoxygenation of 5-ethyl-2-picoline N-oxide with benzyl sulfonyl chloride was elucidated. Two new methods for the deoxygenation of pyridine N-oxides were discovered. The sulfonyl chloride rearrangement of 2-picolin N-oxides was extended to include sulfonic acid anhydrides and sulfonyl bromides. The selective reduction of cyanopyridines to pyridinecarboxaldehydes with Raney nickel was ivestigated. The conversion of 2-pyridinemethanols to their oximes via the 2-sulfonate esters was demonstrated. The oxidation of 2-pyridine methanols to the corresponding aldehydes with manganese dioxide gave moderate yields. Oxidation of 2-pyridine methanols with t-butyl hypochloride gave the aldehyde in yields of 45 to 57%. 2-Pyridin aldoxime methochloride was prepared from 2-pyridine methanol by a new sequence involving (1) quaternization with methyl iodide, (2) conversion to the 2-chloromethyl analog with thionyl chloride and (3) reaction with hydroxylamine; the overall yield was 56%. The conversion of 4-picoline N-oxide to 4-pyridine aldoxime via anil formation, acid hydrolysis, and oxime formation was successful. (Author)