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The aryl group controls the α/γ regioselectivity in deuterations of 2‐( p ‐substituted benzyl)‐4,6‐dimethylpyrylium salts (1)
Author(s) -
Balaban Alexandru T.,
Gheorghiu Mircea D.,
Balaban Teodor Silviu
Publication year - 1983
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.2580200907
Subject(s) - chemistry , methylene , regioselectivity , aryl , medicinal chemistry , intramolecular force , methyl group , ring (chemistry) , deuterium , perchlorate , stereochemistry , methyl formate , group (periodic table) , organic chemistry , methanol , catalysis , ion , alkyl , physics , quantum mechanics
A kinetic study is reported for the deuteration (in sodium formate‐con‐taning HCOOD at 50–73°) of 2‐benzyl‐4,6‐dimethylpyrylium perchlorate and of its derivatives possessing para ‐substituents at the phenyl ring (NO 2 , Cl, Me, OMe). Intramolecular comparison of deuteration rates indicates that the 4‐methyl is always deuterated 8–10 times faster than the 6‐methyl; however, the 2‐methylene group is deuterated with a rate dictated by the nature of the aryl group : faster than the 4‐methyl with p ‐NO 2 and p ‐C1 substituents, more slowly than the γ‐methyl group with p ‐Me and p ‐OMe substituents. Hammett plots show good correlations for relative deuteration rates of the methylene group, and for 1 H‐NMR chemical shifts for methyl and methylene protons.