- SYNTHESIS OF SUBSTITUTED BENZENOIDS AND BIPHENYLS VIA DIELS-ALDER CYCLOADDITION OF 6-METHOXY-2-PYRONES
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A convenient synthesis of substituted 6-methoxy-2-pyrones from alkyl and aryl esters is described.These pyrones undergo Diels-Alder reactions with acetylenic dienophiles to provide an efficient route to polysubstituted benzoates, phthalates and biphenyls.
- Ahmed, Salman A.,Bardshiri, Esfandiar,Simpson, Thomas J.
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p. 1595 - 1596
(2007/10/02)
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- Syntheses of Highly Substituted Benzenes via Diels-Alder Reactions with 2H-Pyran-2-ones
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The 2H-pyran-2-ones (α-pyrones) 1 react as dienes in Diels-Alder reactions with acetylene derivatives.The primarely formed cycloadducts immediately aromatize to benzenes by CO2 elimination.Thus, methyl acetylenedicarboxylate (2a) gives dimethyl phthalates 3, and methyl acetylenediphosphonate (2b) gives dimethyl 1,2-phenylenediphosphonates 8.The reactions of 1-(dimethylamino)-1-methoxyethene (9) with 1 regioselectively produce N,N-dimethylanilines 10 and isomeric homophthalate derivatives 12.Naphthoquinones 14 could be generated from 1,4-benzoquinone (13) and 1 in the presence of acetic anhydride and Pd/C.Hydroxy-2H-pyran-2-ones 4 react via their trimethylsilyl ether 6 analogously with 2a to give dimethyl (trimethylsiloxy)phthalates 7 which are easily converted to phenols 5 by acid-catalyzed hydrolysis.
- Ziegler, Thomas,Layh, Marcus,Effenberger, Franz
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p. 1347 - 1356
(2007/10/02)
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