Cyclobutylidenecyclopropane (7) was prepared in multigram quantities by a new three-step sequence starting from ethyl cyclobutanecarboxylate (4) (39% overall yield). 1,3-Dipolar cycloadditions of phenyl- (9), pyridyl- (10), and the newly prepared (four steps, 43% overall yield) spirocyclic nitrone 11 onto 7 resulted in the regioselective formation of the corresponding adducts 15-17, with the spirobutane moieties adjacent to the oxygen atom in the oxazolidine rings, in 52, Cyclobutylidenecyclopropane (7) was prepared in multigram quantities by a new three-step sequence starting from ethyl cyclobutanecarboxylate (4) (39% overall yield). 1,3-Dipolar cycloadditions of phenyl- (9), pyridyl- (10), and the newly prepared (four steps, 43% overall yield) spirocyclic nitrone 11 onto 7 resulted in the regioselective formation of the corresponding adducts 15-17, with the spirobutane moieties adjacent to the oxygen atom in the oxazolidine rings, in 52, 84, and 48% yields, respectively. Under flash vacuum pyrolysis conditions, the cycloadducts 15-17 underwent thermal rearrangement with opening of the four-membered ring, to afford the spirocyclopropanated azepinones 21-23 in 32, 30, and 19% yields, respectively. In the case of 17, the indolizidinone 25 was also isolated (13% yield). Mechanistically this rearrangement is interpreted in terms of a cyclobutylmethylto- penten-5-yl radical rearrangement.

Cyclobutylidenecyclopropane: New Synthesis and Use in 1,3-Dipolar Cycloadditions - A Direct Route to Spirocyclopropane-Annelated Azepinone Derivatives / A. de Meijere; M. von Seebach; S. I. Kozhushkov; R. Boese; D. Bläser; S. Cicchi; T. Dimoulas; A. Brandi. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - STAMPA. - 2001:(2001), pp. 3789-3795.

Cyclobutylidenecyclopropane: New Synthesis and Use in 1,3-Dipolar Cycloadditions - A Direct Route to Spirocyclopropane-Annelated Azepinone Derivatives

CICCHI, STEFANO;BRANDI, ALBERTO
2001

Abstract

Cyclobutylidenecyclopropane (7) was prepared in multigram quantities by a new three-step sequence starting from ethyl cyclobutanecarboxylate (4) (39% overall yield). 1,3-Dipolar cycloadditions of phenyl- (9), pyridyl- (10), and the newly prepared (four steps, 43% overall yield) spirocyclic nitrone 11 onto 7 resulted in the regioselective formation of the corresponding adducts 15-17, with the spirobutane moieties adjacent to the oxygen atom in the oxazolidine rings, in 52, Cyclobutylidenecyclopropane (7) was prepared in multigram quantities by a new three-step sequence starting from ethyl cyclobutanecarboxylate (4) (39% overall yield). 1,3-Dipolar cycloadditions of phenyl- (9), pyridyl- (10), and the newly prepared (four steps, 43% overall yield) spirocyclic nitrone 11 onto 7 resulted in the regioselective formation of the corresponding adducts 15-17, with the spirobutane moieties adjacent to the oxygen atom in the oxazolidine rings, in 52, 84, and 48% yields, respectively. Under flash vacuum pyrolysis conditions, the cycloadducts 15-17 underwent thermal rearrangement with opening of the four-membered ring, to afford the spirocyclopropanated azepinones 21-23 in 32, 30, and 19% yields, respectively. In the case of 17, the indolizidinone 25 was also isolated (13% yield). Mechanistically this rearrangement is interpreted in terms of a cyclobutylmethylto- penten-5-yl radical rearrangement.
2001
2001
3789
3795
A. de Meijere; M. von Seebach; S. I. Kozhushkov; R. Boese; D. Bläser; S. Cicchi; T. Dimoulas; A. Brandi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/313126
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