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Synthetic Approaches to cularines . III. Nucleophilic addition and substitution
Author(s) -
De Lera Angel Rodríguez,
Sa á José M.,
Suau Rafael,
Castedo Luis
Publication year - 1987
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570240314
Subject(s) - chemistry , ring (chemistry) , aryne , nucleophilic substitution , nucleophile , nucleophilic aromatic substitution , quinone methide , indolizine , medicinal chemistry , phenol , substitution reaction , stereochemistry , quinone , organic chemistry , catalysis
Attempts to induce the formation of the dibenzoxepine ring of cularine compounds by generating an electron‐deficient system in ring C of an 8‐hydroxybenzylisoquinoline met with failure. Attack by C‐8 phenol on a “p‐quinone methide” intermediate afforded benzofurans 16 , which it has been suggested are intermediates in the biogenesis of quettamines. Among the nucleophilic substitution reactions tried, only that based on a phenoxide attack on a benzyne intermediate (generated by dimsyl sodium treatment of a 2′‐bromo‐8‐hydroxybenzylisoquinoline) afforded the dibenzoxepine nucleus of tetradehydrocularines 25 and 27. Competing N‐attack afforded the indolizine skeleton present in 24 and 26. From compounds 25 and 27 , the corresponding cularines, cularimines and oxocularines were obtained.