155108-45-5Relevant articles and documents
Convenient Synthesis of 2,2-Diethoxy-2,5-dihydrofurans, 2(5H)Furanones and 2-Ethoxyfurans. Crystal and Molecular Structure of a Barrelenone Diels-Alder Product
Saalfrank, Rolf W.,Hafner, Wieland,Markmann, Joachim,Welch, Andreas,Peters, Karl,Schnering, Hans Georg von
, p. 389 - 406 (2007/10/02)
Reaction of 1,2-hydroxyketones 5 with (2,2-diethoxyvinylidene)triphenylphosphorane (2) or (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborates 6 yields the 2,2-diethoxy-2,5-dihydrofurans 9.Depending on the reaction conditions used, the orthoesters 9 can be hydrolized to give 2(5H)furanones 10 and 2-ethoxyfurans 11, respectively. 4,5-Dimethyl-5,6-dihydro-2-pyranone (20) and 8-methoxycoumarin (23) are prepared, starting from (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborate (6a) and 1-hydroxy-2-methyl-3-butanone (16) or 2-hydroxy-3-methoxy-benzaldehyde (21).The 2-ethoxyfuranes 11 readily undergo Diels-Alder reactions with 2-chloracrylonitrile (24), maleic anhydride (26), N-phenyl-1,2,4-triazoline-3,5-dione (28) and dimethyl acetylenedicarboxylate (30) to give the corresponding Diels-Alder products 25, 27, 29 and 31, respectively.Contrary to 2-ethoxyfuran 11b, 11a reacts with two equivalents of acetylene 30, to yield barrelenone 34.The structure of 34 unequivocally is established by X-ray structure analysis. - Keywords: 2,2-Diethoxy-2,5-dihydrofurans, 2(5H)Furanones, 2-Ethoxyfurans, Barrelenone, Diels-Alder Products, X-Ray
