86997-04-8Relevant academic research and scientific papers
Cycloadditions of 6-Oxo-1,3,4-oxadiazines (4,5-Diaza-α-pyrones), 3. Reactions of 6-Oxo-2,5-diaryl-1,3,4-oxadiazines with Alkenes
Christl, Manfred,Lanzendoerfer, Ulrike,Hegmann, Joachim,Peters, Karl,Peters, Eva-Maria,Schnering, Hans Georg von
, p. 2940 - 2973 (2007/10/02)
Cycloaddition of the known 6-oxo-2,5-diphenyl-6H-1,3,4-oxadiazine (1a) and the new 2,5-diaryl derivatives 1b - g with various alkenes yield nitrogen free products.Using cyclopropenes and cyclobutene, α,β-unsaturated seven-membered enollactones 42 - 45 and the α,β-unsaturated eight-membered enollactone 47 are formed, respectively.In the presence of basic aluminum oxide 42a and d undergo a hydrogen migration to form the β,γ-unsaturated enollactones 46a and d, respectively.With other alkenes, γ-ketoketenes 33 have been observed, or are assumed to be intermediates, based on the structure of the isolated products.The six-membered eno llactones 10, 13, 15, 19, and 21 and 22 have been obtained with norbornene, norbornadiene, cyclopentene, trans-cyclooctene, and styrene.Compound 10 isomerizes to 34 on treatment with potassium tert-butoxide.The methanolyses of these enollactones result in the formation of the diastereomeric methyl esters 12 and 35.The γ-ketoketene 16 formed from trans-cyclooctene gives acid 17 and ester 18 with water and methanol, respectively.These reactions are faster than the cyclization to enollactone 19.From cis,trans-1,5-cyclooctadiene the more short-lived γ-ketoketene 40 is formed, which undergoes intramolecular cycloaddition, giving rise to the tricyclic cyclobutanone derivative 41.Tetracyclic products of type 4 are generated from benzvalene (2) and 1.The structures and configurations of compounds 10, 19, and 41 have been determined by means of X-ray analyses.
