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Synthesis of New Quinoxaline Derivatives by Reductive Cyclization of Various 1‐(2‐Nitrophenyl)‐2‐cyanoamines
Author(s) -
Renaud Tristan,
Hurvois JeanPierre,
Uriac Philippe
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200103)2001:5<987::aid-ejoc987>3.0.co;2-b
Subject(s) - chemistry , cyanation , morpholine , substituent , moiety , medicinal chemistry , catalysis , piperidine , amidine , hydroxylamine , hydroamination , stereoselectivity , quinoxaline , nitrile , organic chemistry
The electrochemical cyanation of various six‐membered N ‐(2‐nitrophenyl) heterocyclic amines, including piperidine, morpholine, thiomorpholine, and N ‐Boc‐protected piperazine derivatives, was investigated. The expected cyanoamines 5 were obtained in good yields and subjected to catalytic hydrogenation to afford the corresponding cyclic amidine N ‐oxides 6 . The reductive cyclization proceeded through the formation of a hydroxylamine, which cyclized onto the cyano moiety. The stereoselectivity of the cyclization reaction was studied for the cases both of trans ‐ 5f , in which the 2‐cyano substituent was axial and the 4‐methyl substituent equatorial, and of cis ‐ 5f , in which both the 2‐cyano and the 4‐methyl substituents were equatorial. The expected tetrahydroquinoxalines 3 were conveniently prepared in a following step by the catalytic hydrogenation of cyclic amidines 6 in the presence of Pearlman’s catalyst at five atmospheres of hydrogen pressure.