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On the Regioselectivity of Imidoyl Radical Cyclisations
Author(s) -
Nanni Daniele,
Calestani Gianluca,
Leardini Rino,
Zanardi Giuseppe
Publication year - 2000
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/(sici)1099-0690(200003)2000:5<707::aid-ejoc707>3.0.co;2-i
Subject(s) - chemistry , regioselectivity , sulfanyl , radical , quinoxaline , aryl , moiety , isocyanide , medicinal chemistry , aryl radical , derivative (finance) , ring (chemistry) , photochemistry , stereochemistry , organic chemistry , alkyl , financial economics , economics , catalysis
The previously reported tandem cyclisation of N ‐aryl α‐(2‐cyanophenyl)sulfanyl imidoyl radicals affords one quinoxaline derivative arising from exclusive 1,6‐cyclisation of the final iminyl radical onto the N ‐aryl ring. When the imidoyl radicals are generated by addition of photolytically generated (2‐cyanophenyl)sulfanyl radicals to isocyanides, the reaction also gives small amounts of a by‐product that is formed by an analogous route and whose X‐ray crystallographic data are reported here. The formation of this product entails a rare ortho ‐selective photo‐Fries rearrangement of the starting disulfide, followed by addition to the isocyanide and regioselective 1,5‐cyclisation of the resulting imidoyl onto only one of the two available radical acceptors, i.e. the cyano group and the sulfide moiety. Semiempirical MNDO‐d calculations were performed in order to throw some light on the factors affecting these competitive cyclisations.