Rhodium (I)-katalysierte Reaktionen der [2+4]-Cycloaddukte aus 3,4-Dimethoxyfuran und Acetylendicarbonsäure-estern |
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| Authors: | Peter Xaver Iten Conrad Hans Eugster |
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| Abstract: | 2+4]-Cycloaddition Products of 3,4-Dimethoxyfuran with Acetylenedicarboxylates and Their Transformations under the Influence of Rhodium(I) Catalysts 3,4-Dimethoxyfuran ( 1 ) readily reacts with acetylenedicarboxylates ( 2 ) at room temperature in a 2+4]-cycloaddition to give a mono-( 3 ) and several di-addition products. 90% of the latter consists of the endo-exo compound 4 . Under the influence of catalytic amounts of Rh(CO)2Cl]2 the mixture of mono- and di-adducts in methanolic solution is smoothly transformed into endo-5,5,6-trimethoxy-7-oxabicyclo 2.2.1]hept-2-ene-2,3-dicarboxylate 1 Alle Verbindungen sind racemisch. Die Formeln stellen jeweils nur ein Enantiomeres dar. (5) , 3-hydroxy-4,5-dimethoxyphthalate ( 6 ) and (I R *, 2 S *, 4 R *, 5 R *, 7 R *, 11 R *, 12 R *) -5,8,8,9,12-pentamethoxy-3,6-dioxatetracyclo 5.3.1.1 2,5 . 0 4,11 ]dodec-9-ene-1,11-dicarboxylate ( 7 ). |
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