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Furopyridines. X . Synthesis of tricyclic heterocycles, furo[2,3‐ b :4,5‐ c' ]‐, furo[3,2‐ b :4,5‐ c' ]‐, furo[2,3‐ c :4,5‐ c' ]‐ and furo[3,2‐ c :4,5‐ c' ]dipyridine
Author(s) -
Shiotani Shunsaku,
Morita Hiroyuki
Publication year - 1990
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.5570270330
Subject(s) - chemistry , tricyclic , ethyl chloroformate , sodium azide , medicinal chemistry , organic chemistry , malonic acid
This paper describes the synthesis of four tricyclic heterocycles, furo[2,3–6:4,5‐ c' ]‐ ( 5a ), furo[3,2‐ b :4,5‐ c' ]‐ ( 5b ), furo[2,3‐ c :4,5‐ c' ]‐ ( 5c ) and furo[3,2‐ c :4,5‐ c' ]dipyridine ( 5d ). Starting with 2‐formylfuropyridines ( 1a‐d ), β‐(2‐furopyridyl)acrylic acids 2a‐d were obtained by condensing with malonic acid. The acrylic acids were converted to the acid azides by reaction with ethyl chloroformate and the subsequent reaction with sodium azide. Heating of the acid azides at 230–240° with diphenylmethane and tributylamine gave tricyclic pyridinones 3a‐d , which were converted to the respective chloro derivatives 4a‐d by reaction with phosphorus oxychloride. Reduction of the chloro compounds over palladium‐charcoal yielded compounds 5a‐d respectively. All the compounds 2 to 5 were characterized by elemental analysis and spectral data. The H and 13 C nmr and electronic spectral features of the furodipyridines were discussed comparing with those of the parent furopyridines.