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Synthesis of symmetrical 2,2′,4,4′‐tetrasubstituted[4,4′‐bioxazole]‐5,5′(4 H ,4′ H )‐diones and their reactions with some nucleophiles
Author(s) -
Andersen Kenneth K.,
Gloster Daniel F.,
Bray Diana D.,
Shoja Massud,
Kjær Anders
Publication year - 1998
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.5570350210
Subject(s) - chemistry , nucleophile , isomerization , radical , amine gas treating , amide , methanol , nuclear magnetic resonance spectroscopy , medicinal chemistry , carbon fibers , stereochemistry , organic chemistry , catalysis , materials science , composite number , composite material
Several symmetrical 2,2′,4,4′‐tetrasubstituted[4,4′‐bioxazole]‐5,5′(4 H ,4′ H )‐diones 1a‐f were obtained by dehydrodimerization of 5(4 H )‐oxazolones 2a‐f . The configurations of four were established; one by X‐ray crystallography rac ‐ 1c , and three rac ‐ 1a , meso ‐ 1a and rac ‐ 1b by 1 H nmr spectroscopy of their derivatives. Upon being heated, the bioxazolones isomerized, presumably by breakage of the 4,4′‐carboncarbon bond to form free radicals followed by their recombination. The results of a crossover experiment were consistent with a radical nature for this isomerization reaction. Treatment of three of the bioxazolones rac ‐ 1a , meso ‐ 1a and rac ‐ 1c with methanol and amine nucleophiles led to ester and amide derivatives 7–11 of α,α'‐dehydrodimeric amino acids.