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Diazoniapentaphenes. Synthesis from pyridine‐2‐carboxaldehyde and structural verifications
Author(s) -
Krapcho A. Paul,
Cadamuro Sergio A.
Publication year - 2004
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.5570410224
Subject(s) - chemistry , pyridinium , pyridine , aldehyde , tribromide , bromine , medicinal chemistry , nuclear magnetic resonance spectroscopy , organic chemistry , catalysis
Reactions of pyridine‐2‐carboxaldehyde (9) with α,α′‐dibromo‐ o ‐ and p ‐xylenes led to the corresponding bis‐pyridinium aldehydes 10 and 14. These aldehydes were quite reactive and the respective hydrates 11 and 15 were also formed. Cyclization of 10 or 11 with 48% HBr led to 12 while cyclization with PPA followed by conversion to the bis tribromide and loss of bromine led to 1. Cyclization of 14 or 15 with 48% HBr led to 3. Attempts to react α,α′‐dibromo‐ m ‐xylene with pyridine‐2‐carboxaldehyde (9) were not successful for the preparation of the bis‐pyridinium aldehyde 13. The bis‐pyridinium acetals 4, 5 and 6 were prepared and cyclized to afford 1, 2 and 3 , respectively, by the previously reported procedures. The structures of 1 and 2 were verified by 1 H‐NMR and 13 C‐NMR spectroscopy while that of 3 was confirmed by X‐ray analysis.