ChemInform Abstract: COBALT‐CATALYZED CYCLOADDITION OF ALKYNES AND NITRILES TO PYRIDINES: A NEW ROUTE TO PYRIDOXINE (VITAMIN B6)

Abstract

SummaryA new synthesis of pyridoxine hydrochloride (1) based on a Co-catalyzed cycloaddition of MeCN with substituted di(2-propynyl) ethers (3 and 16) is described. The reaction sequences following cycloaddition and leading to 1 involve as key steps the rearrangement of the pyridine-N-oxide 6 to the 3-hydroxypyridine 7 with Ac,O and a modified Curtius rearrangement of the acid 19 and subsequent diazotation and hydrolysis to the same pyridoxine precursor 7, respectively. The intermediate 7 is transformed to 1 by well-known procedures.