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Intramolecular Photocycloaddition of N ‐Alkenyl Substituted Maleimides: A Potential Tool for the Rapid Construction of Perhydroazaazulene Alkaloids
Author(s) -
BookerMilburn Kevin I.,
Anson Christopher E.,
Clissold Cole,
Costin Nicola J.,
Dainty Richard F.,
Murray Martin,
Patel Dhiren,
Sharpe Andrew
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(200104)2001:8<1473::aid-ejoc1473>3.0.co;2-w
Subject(s) - chemistry , intramolecular force , stereoselectivity , maleimide , cycloaddition , alkene , cyclobutane , ring (chemistry) , yield (engineering) , stereochemistry , mitsunobu reaction , side chain , intramolecular reaction , substrate (aquarium) , organic chemistry , materials science , polymer , oceanography , metallurgy , geology , catalysis
UV irradiation of a number of N ‐alkenyl‐substituted maleimide derivatives leads to the formation of complex perhydroazaazulenes in excellent yields. The overall process can be considered as a formal intramolecular [5+2] cycloaddition. Substrates were prepared by Mitsunobu coupling of the appropriate alkenols with various maleimides. Methyl substitution of the alkenyl side chain gave the cycloadducts 13a − g in good yields, with moderate to high stereoselectivity being observed for 13e and 13g , respectively. Use of cyclic alkene side chains led to the formation of tri‐ and tetracyclic products with high degrees of stereoselectivity in most cases. Some of the polycyclic ring systems that were prepared constitute the core skeleton of a number of complex alkaloids. The substrate 29 underwent an unexpected [2+2] photocycloaddition to yield the unusual cyclobutane 31 .