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Aza‐ ortho ‐xylylenes in Organic Synthesis
Author(s) -
Wojciechowski Krzysztof
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(200110)2001:19<3587::aid-ejoc3587>3.0.co;2-5
Subject(s) - chemistry , methylene , nucleophile , isomerization , cycloaddition , reactive intermediate , valence (chemistry) , medicinal chemistry , organic chemistry , catalysis
Aza‐ ortho ‐xylylenes ( ortho ‐quinone methylene imines or 1‐methylene‐6‐iminocyclohexa‐2,4‐dienes) are potential building blocks for the construction of heterocyclic systems. These reactive, non‐isolable intermediates may be generated by a variety of procedures, such as cheletropic extrusion of SO 2 from benzosultams, [4+2] cycloreversion of 3,1‐benzoxazin‐2‐ones, or by 1,4‐elimination of various species (H 2 O, R 2 NH, HCl, HF) from 2‐aminobenzyl derivatives. The aza‐ ortho ‐xylylenes enter into [4+2] cycloaddition reactions, producing condensed heterocycles. In numerous cases, aza‐ ortho ‐xylylenes undergo [1,5]‐sigmatropic hydrogen shifts to afford 2‐vinylaniline derivatives, while addition of nucleophiles to them gives rise to 2‐aminobenzyl derivatives. The problem of stability and valence isomerization of benzazetidines to aza‐ ortho ‐xylylenes is discussed. A brief survey of methods of synthesis of precursors suitable for generation of aza‐ ortho ‐xylylenes is also included.