Collect. Czech. Chem. Commun. 2000, 65, 1911-1938
https://doi.org/10.1135/cccc20001911

Dichotomy in the Ring Opening Reaction of 5-[(2-Furyl)methylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione with Cyclic Secondary Amines

Peter Šafářa,*, František Považaneca, Naďa Prónayováb, Peter Baranc, Guido Kickelbickd, Jozef Kožíšeke and Martin Brezaf

a Department of Organic Chemistry, Slovak Technical University, SK-812 37 Bratislava, Slovak Republic
b Central Laboratory, Slovak Technical University, SK-812 37 Bratislava, Slovak Republic
c Department of Chemistry, University of Cyril and Methodius, nám. J. Herdu 2, SK-917 01 Trnava, Slovak Republic
d Institut für Anorganische Chemie, Technische Universität Wien, Getreidemarkt 9/153, A-1060 Wien, Austria
e Department of Inorganic Chemistry, Slovak Technical University, SK-812 37 Bratislava, Slovak Republic
f Department of Physical Chemistry, Slovak Technical University, SK-812 37 Bratislava, Slovak Republic

Abstract

5-[(2-Furyl)methylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione (1a) treated with equimolar amount of pyrrolidine or hexahydroazepine afforded 5-(pyrrolidine)- (2a) or 5-[(hexahydro- azepine-1-yl)-2-hydroxypenta-2,4-dien-1-ylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione (2d). Their treatment with hydrobromic acid led to cyclization and formation of stable 5-cyclopentenyl-4H-1,3-dioxine hydrobromides (3a, 3d). Under the same conditions 1a treated with morpholine or piperidine yielded a mixture of 2b, 3b and 2c, 3c, respectively. The corresponding 3-substituted furans 1b-1e gave only substituted 5-cyclopentenyl-4H-1,3-dioxines (3e-3i). The use of an excess amine in reaction with 1a yielded unexpectedly 5-(3,5-dihetaryl-cyclopent-2-en-1-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-diones (9a-9c) and 5-[5-hexahydroazepin-1-ium-1-ylidene-2-(hexahydroazepin-1-yl)cyclopent-1-en-1-yl]-2,2-dimethyl-4-oxo-4H-1,3-dioxin-6-olates (10).

Keywords: Substituted Meldrum's acids; 4H-1,3-Dioxines; Cyclopentenones; Furans; Amides; Ring opening; Cyclizations; Crystal structure; Reaction mechanisms.

References: 29 live references.