S u m m a r y 2,3-Dihydroazete 1-oxides (3b-e), the first examples of crystalline, 'stable,' four-membered cyclic nitrones, are formed by reaction of 1-nitroalkenes with ynamines, and other products are 3-nitrocyclobutenes ;the structure of the cyclic nitrone (3b) has been determined by X-ray crystallography.CYCLOBUTENES are formed thermally under mild conditions either by reaction of electron-rich alkenes (e.g. enamines) with electron-deficient acetylenes [acetylene(di)carboxylic acid esters' 9 , or 1-t-butyl-2-nitr~acetylene~] or by reaction of electron-deficient alkenes (e.g. 1-cyanoalkenes) with electron-rich acetylenes (ynamines4 9 5 ) . We describe here the reactions of 1-nitroalkenes and ynamines.1-Nitrocyclopentene (la)6 was treated with an equimolar amount of l-phenyl-2-(pyrrolidin-l-yl)acetylene (2a) in light petroleum for 16 h at room temperature. A tan precipitate was filtered off,? and orange crystals (m.p. 80-81 "C; 40% yield) were obtained from the filtrate. This product was identified as the bicycloheptene (4a); lH n.ni.
3‐Nitro‐(b)‐benzofuran (I) reagiert mit dem Inamin (II) zunächst zu einem Addukt (III), das sich über die polare Zwischenstufe (IV) in den Tricyclus (V) umlagert.
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