Davidson cyclization

Scheme 2.33. Alternating benzene/imidazole systems via Ugi-4CR and Davidson cyclization.

The Ugi-4CR provides straightforward access to precursors of the pyrazine ring that are suitable for a Davidson cyclization [72], The reaction between arylglyoxals, amines, isocyanides, and benzoylformic acid in ether afforded adducts 114, which cyclized on treatment with an excess of ammonium acetate in acetic acid to give pyrazine carboxamides 115 (Scheme 2.41). 

R. S. Davidson, J. W. Goodwin and G. Kemp, Advances in Physical Organic Chemistry, voi. 20, Academic Press (1984), p. 191. The photochemistry of aryl halides and related compounds is reviewed, including substitution and cyclization reactions. 

Clark, A. E., Davidson, E. R., Zaleski, J. M. UDFT and MCSCF Descriptions of the Photochemical Bergman Cyclization of Enediynes. J. 

Other references related to the Davidson oxazole cyclization are cited in the literature. ... 

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