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Cycloadditionen von 3,4‐Dimethoxyfuran an Dienophile
Author(s) -
Iten Peter Xaver,
Hofmann Alfred André,
Eugster Conrad Hans
Publication year - 1979
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19790620717
Subject(s) - chemistry , maleic anhydride , adduct , furan , ozonolysis , stereospecificity , nucleophile , cycloaddition , tetrahydrofuran , medicinal chemistry , organic chemistry , halogen , phthalic anhydride , catalysis , solvent , polymer , alkyl , copolymer
On cycloaddition reactions with 3,4‐dimethoxyfuran We describe new cycloadditions of 3,4‐dimethoxyfuran (3,4‐DF, 1 ) with various dienophiles. In contrast to furan, the reaction of 3,4‐DF with maleic anhydride gives exo ‐ and endo ‐adducts at approximately the same rate. The thermodynamically more stable product is again the exo ‐product. Less active dienophiles lead also to mixtures of exo ‐ and endo ‐adducts, except for citraconic anhydride (methylmaleic anhydride) which forms only the adduct with an endo ‐methyl group. Dimethylmaleic anhydride could not be reacted with 3,4‐DF. All adducts with 3,4‐DF contain a hidden 1,2‐dicarbonyl group in the form of an endiolether. Its pronounced nucleophilic character allows a series of further additions. Noteworthy are the stereospecific cis ‐additions of halogens and the preparation of several acetals. Ozonolysis of the enolether in 4 allows the preparation of the hitherto unknown 2 r , 3 trans , 4 trans , 5 cis ‐tetrahydrofuran tetracarboxylic acid and derivatives thereof ( 5 and 6 ).