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Allenes as the π‐Component in Electrocyclization Reactions: Transformation of 1,3,4‐Pentatrienyl Azomethine Ylides into Seven‐Membered Heterocycles
Author(s) -
Knobloch Karin,
Eberbach Wolfgang
Publication year - 2002
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(200207)2002:13<2054::aid-ejoc2054>3.0.co;2-m
Subject(s) - chemistry , allene , isomerization , ring (chemistry) , pyridinium , medicinal chemistry , base (topology) , propargyl , annulation , bromide , cycloaddition , organic chemistry , catalysis , mathematical analysis , mathematics
Upon treatment of the pyridinium bromides 8a − c , obtained by quaternization of pyridines 7 with the allyl bromide 6 , with base, the annulated methylene pyridoazepines 10a − c are formed. The reaction pathway includes base‐catalysed propargyl‐allene isomerization and dipole formation as the first steps followed by the ring closure of [ 9 ] to 10 . The latter process represents the first example of the participation of an allene unit in 1,7‐electrocyclization reactions of extended azomethine ylides. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)