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The versatile chemistry of thiophenes: The effects of b ‐side contra c ‐side annelation on reactivity
Author(s) -
Gronowitz Salo
Publication year - 1994
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.5570310306
Subject(s) - chemistry , annulation , reactivity (psychology) , pyridine , cycloaddition , ring (chemistry) , medicinal chemistry , metalation , electrophile , electrophilic substitution , reagent , nitration , organic chemistry , stereochemistry , catalysis , medicine , alternative medicine , pathology
The synthesis of the nine dithienopyridines and twenty‐four thienonaphthyridines with angular annelation is described. They are all conveniently obtained by Pd(0)‐catalysed couplings between heterocyclic o ‐formylboronic acids or o ‐formylstannyl derivatives with heterocyclic o ‐amino‐halo derivatives. The effect of the use of silver oxide and cupric oxide as co‐reagent is discussed. Differences in electrophilic substitution, metalation and cycloaddition of b ‐ and c ‐fused isomers is treated. Theoretical calculations at the RHF/3–21G* level are in agreement with the orientation and reactivity in the nitration of dithieno[3,4‐ b :3′,4′‐ d ] pyridine and dithieno[2,3‐ b :3′,2′‐ d ] pyridine observed experimentally. The preparation of N ‐oxides of the above‐mentioned ring‐systems and their reactivity will also be discussed.