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Mechanism of the Bischler–Napieralski exocyclic and endocyclic dehydration products in the radiosynthesis of ( R )‐(‐)‐[6a‐ 14 C]apomorphine
Author(s) -
Kitson Sean L.
Publication year - 2007
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.1270
Subject(s) - chemistry , isoquinoline , acetamide , apomorphine , dehydration , radiosynthesis , organic chemistry , medicinal chemistry , stereochemistry , biology , biochemistry , receptor , microbiology and biotechnology , in vivo , agonist
This paper will outline the mechanism of the Bischler–Napieralski cyclodehydration for the radiosynthesis of ( R )‐(‐)‐[6a‐ 14 C]apomorphine 1 . The carbon‐14 radiosynthesis of ( R )‐(‐)‐[6a‐ 14 C]apomorphine was first reported by Kitson and Knagg in May 2006. The Bischler–Napieralski cyclodehydration of 3,4‐dimethoxy‐2‐nitrophenyl‐ N ‐phenethyl[carboxyl‐ 14 C]acetamide 5 was initiated using a mixture of P 2 O 5 /POCl 3 in refluxing toluene. This generated the endocyclic dehydration product 1‐(3,4‐dimethoxy‐2‐nitrobenzyl)dihydro[1‐ 14 C]isoquinoline 4 . The Bischler–Napieralski endocyclic dehydration by‐product was identified from 1 H NMR and MS to be 3‐(6,7‐dimethoxyanthranil)‐dihydro[1‐ 14 C]isoquinoline 7 . The action of POCl 3 in acetonitrile on 3,4‐dimethoxy‐2‐nitrophenyl‐ N ‐phenethyl[carboxyl‐ 14 C]acetamide 5 gave exclusively the exocyclic dehydration product 1‐(3,4‐dimethoxy‐2‐nitrobenzal)‐1,2,3,4‐tetrahydro[1‐ 14 C]isoquinoline 8 . Copyright © 2007 John Wiley & Sons, Ltd.