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Cycloadditionen von 6 H ‐1,3,4‐Oxadiazin‐6‐onen (4,5‐Diaza‐α‐pyronen), 15. Reaktionen von 6 H ‐1,3,4‐Oxadiazin‐6‐onen mit Norbornadien. Ein neuer Weg zu 3,6‐disubstituierten α‐Pyronen
Author(s) -
Christl Manfred,
Bodenschatz Gabriele,
Feineis Erich,
Hegmann Joachim,
Hüttner Gerhard,
Mertelmeyer Stefan,
Schätzlein Klaus
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960533
Subject(s) - chemistry , boron trifluoride , medicinal chemistry , trifluoroacetic acid , ether , lewis acids and bases , enol , ketene , organic chemistry , catalysis
Cycloadditions of 6 H ‐1,2,4‐Oxadiazin‐6‐ones (4,5‐Diaza‐α‐pyrones), 15. Part 14: Ref. [1] . — Reactions of 6 H ‐1,3,4‐Oxadiazin‐6‐ones with Norbornadiene. A New Route to 3,6‐Disubstituted α‐Pyrones Upon reaction with norbornadiene, ten disubstituted 1,3,4‐oxadiazin‐6‐ones 1 were converted into 3,6‐disubstituted α‐pyrones 6 . For this purpose, solutions of the substrates were treated with boron trifluoride‐ether or trifluoroacetic acid. The smooth formation of 6 was also observed when a γ‐oxo ketene, initially generated by heating a solution of the substrates in the absence of boron trifluoride–ether, was allowed to react with the Lewis acid. Without use of an acid, only 6f could be obtained free from further compounds, whereas in the other cases enol lactones and 1:2 products of the types 8 and 7 were formed additionally. Oxadiazinone 1j gave enol lactone 10 in the noncatalysed reaction.