Unprecedented Reactivity of 5-Substituted 3-Hydroxy-1,2,3,4-tetrahydroquinoline-2,4-diones with Ethyl (Triphenylphosphoranylidene)acetate

Abstract

3,5,8-Trisubstituted 3-hydroxy-1,2,3,4-tetrahydroquinoline-2,4-diones(3) reacted with ethyl (tripbeny1phosphoranylidene)acetate (4) to yield several products.The major products, 4,7-disubstituted 1,3-dihydro-3-phenylacetoxy-Windol-2-ones ( 5) and (ll), were formed via the molecular rearrangement of 3, catalyzed by the strongly basic Wittig reagent.The Wittig reaction at the lactam group of 3, resulting in 2-ethoxycarbonylmethylene derivatives, can be explained by the poor reactivity of the sterically hindered 40x0 group.Under acid catalysis, the Wittig reaction proceeded at the hindered 4 0 x 0 group as well.A series of minor products were also obtained through the Wittig reaction of 3. A reaction mechanism of the molecular rearrangement of substances (3) is proposed.Recently, the reactions of 3-hydroxy-1,2,3,4-tetrahydroquinoline-2,4-diones, natural metabolites of some Pseudomonas species,' with ethyl (triphenylpbosphoranylidene)acetate have been described.'These reactions proceed with high stereoselectivity to give E-4-ethoxycarbonylmethylene-1,2,3,4-tetrahydro-2quinolones.3-Substituted derivatives of 2,3a,4,5-tetrahydrofUro[2,3-c]quinoline-2,4-diones were detected and, in some cases, isolated as the minor products of the Wittig reaction.The independent synthesis of these butenolides by an intramolecular Wittig reaction has also been de~cribed.~The smooth reactivity of 3-hydroxy-1,2,3,4-tetrahydroquinoline-2.4-doe in the Wittig reaction, combined with good yields, stimulated us to further our studies on a set of substrates bearing a large substituent at the position 5 .These, providing the Wittig reaction occurred in the way described previously,2 might lead to products where the newly formed exocyclic double bond would be, due to the