The acid cleavage of 2,5-dialkoxy-2,5-dihydrofuran derivatives is used in organic chemistry for the production of such valuable starting materials for the synthesis of complex natural compounds as malealdehyde [1][2][3][4], fumaraldehyde [3,4], 3-acetylacrolein [1, 2], 3-acetylacrylic acid and its derivatives [5,6], levulinic acid and its derivatives [5,7,8], and also a large number of 1,4-diketones [9][10][11]. The latter are widely used in the synthesis of hydroxycyclopentene derivatives [12][13][14][15][16][17][18].The hydrolytic cleavage of the ring in 2,5-dialkoxy-2,5-dihydrofurans is a complex process, leading to the formation of a multicomponent mixture of unstable reaction products [4][5][6][7][8], the detailed mechanism of which is not yet clear. In the present work we investigated the protolytic cleavage of methyl 3-(2,5-dimethoxy-2,5-dihydro-2-furyl)propionate (I) in the presence of both individual and mixed nucleophiles (water, methanol).Earlier we investigated the use of compound (I) as a readily obtainable starting material in the synthesis of 4-hydroxy-2-methoxycarbonylmethyl-2-cyclopenten-l-one (an intermediate for the production of prostaglandim [19]) and also its thermal stability [20]. In addition, we suppose that the linear products of the cleavage of the investigated compound, i.e., derivatives of 1,4-dienes containing seven carbon atoms, may fred independent use in organic synthesis.The cleavage of compound (i) at pH 2 in dilute hydrochloric acid leads to the formation of the unstable cis-enedione (II). In a weakly alkaline medium it readily undergoes cyclization to 3-hydroxy-2-methoxycarbonylmethyl-4-cyclopenten-l-one [19]. In the presence of a catalytic amount of iodine it isomerizes with a high yield to methyl trans-4,7-dioxohept-5-enoate (HI).
coo. Hop ,. IH -r