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Preparation of selectively side‐chain deuteriated pyridines via pyrylium salts
Author(s) -
Balaban Alexandru T.
Publication year - 1981
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580181108
Subject(s) - chemistry , deuterium , kinetic isotope effect , side chain , alkyl , medicinal chemistry , ammonia , hydrogen–deuterium exchange , methyl radical , organic chemistry , hydrogen , radical , physics , quantum mechanics , polymer
Isotopic exchange of benzylic hydrogens in α‐ and β‐alkyl side‐chains of pyrylium salts occurs readily by heating in deuterium oxide at normal pressure. As β‐hydrogens exchange faster than α‐hydrogens, one may obtain selective (about 90 % isotopic purity) β‐ or α‐deuteriation of side‐chains by direct or reverse isotope exchange. The deuteriated pyrylium salts are converted by aqueous ammonia into the corresponding pyridines without loss of deuterium. Examples presented are : 2,4,6‐tri‐(d 3 ‐methyl)‐, 2,6‐di‐(d 3 ‐methyl)‐4‐methyl‐, 2,6‐dimethyl‐4‐(d 3 ‐methyl)‐, 2,6,‐di‐(d 3 ‐methyl)‐3,5‐dimethyl‐, 2,4,6‐tri‐(d 3 ‐methyl)‐3,5‐di‐methyl‐, 2,6‐di‐(α‐d 2 ‐ethyl)‐4‐(d 3 ‐methyl)‐, 2,6‐diethyl‐4‐(d 3 ‐methyl)‐, and 2,6‐di‐(α‐d 2 ‐ethyl)‐4‐methyl‐pyrylium perchlorates and ‐pyridines.