Domino Inverse Electron Demand Diels—Alder Reactions of Chromones with Ethyl Vinyl Ether.

Abstract

FLOERKE, U.; PESSOA-MAHANA, H.; WEISS-LOPEZ, B.; ESTEVEZ-BRAUN, A.; ARAYA-MATURANA, R.; Heterocycles 71 (2007) 6, 1327-1345; Dep. Chem., Univ. Paderborn, D-33098 Paderborn, Germany; Eng.) -R. Staver 42-129

Ethyl (1R*,10S*,12R*,15S*)-4-Hydroxy-2-oxo-15- (2-oxo-1-pyrrolidinyl)-9-oxatetracyclo[10.2.2.01,10.03,8]hexadeca-3,5,7,13-tetraene-13-carboxylate

“…The relative stereochemistry of these cycloadducts was made analyzing the cis and trans coupling constants between H-10 and H-15 with H-11 and H-16, respectively, and by comparing them with analogs 3 and 4 obtained in the reaction with ethyl vinyl ether [15]. The spectra of 5 and 6 show a very similar coupling pattern in the bicyclic moiety compared to that of 3 and 4 respectively, including a similar 4 JH,H coupling through a W coupling path between the H-16 and H-11 protons in 5.…”

“…Alternatively, IEDDA followed by elimination and oxidation provide xanthone 2 [15] (Scheme 1). 2D NMR experiments along with X-ray crystal crystallography, allowed for the unequivocal assignment of these structures.…”

Effects of Simple and Angular Chromones on Tumor Cell Respiration

“…Generally, the IC 50 for oxygen uptake inhibition is about one order of magnitude greater than the IC 50 for cytotoxicity. In relation to these compounds, spectroscopic and reactivity studies of chromone 4 have also been reported [16,17].…”

“…To a solution of chromone (1 and 2), one equivalent of ethyl (triphenylphosphoranylidene) acetate in toluene was added and heated under reflux for 2 h. A mixture of cis and trans derivatives was obtained, with the latter as the main product. Purification was in accord with procedures previously described [16,17]. General procedure for reduction of formyl chromones: About 1 g basic alumina and about 50 mg (5% of alumina weight) of formyl chromone (1 and 2), dissolved in 10 mL 2-propanol, were placed in a round-bottom flask containing a magnetic bar, and the mixture was stirred for 4 h at 75ºC.…”

“…1 H NMR (300 MHz, CDCl 3 ): 7.52 (ddd, 1H, J 1 = 7.9 Hz, J 2 = 7.2 Hz, J 3 = 1.1 Hz, 6-H), 7.56 (dd, 1H, J 1 = 8.5 Hz, J 2 = 1.1 Hz, 8-H), 7.77 (ddd, 1H, J 1 = 8.5 Hz, J 2 = 7.2 Hz, J 3 = 1.7 Hz, 7-H), 8.32 (dd, 1H, J 1 = 7.9 Hz, J 2 = 1.7 Hz, 5-H), 8.57 (s, 1H, 2-H), 10.40 (s, 1H, CHO). 3-(4-oxo-4H-chromen-3-yl)acrylate (4) [16,17] MP: 111.5-112.5ºC.…”