3,4‐Dimethoxyfuran: Eigenschaften, Berechnungen und Substitutionsreaktionen

Abstract

In memoriam Prof. H. Lubhart(1 1 .x1.77) 3,4-Dimethoxyfuran: Properties, Calculations and some Substitution Reactions Summary 3,4-D6methoxyfuran (3,4-DF) is much more reactive than furan itself. We present experimental details €or the synthesis of this useful compound in 50-100 g batches. 3,4-Dibenzyloxyfuran has also been prepared. Quantum mechanical calculations by PPP-and CNDO-methods analogous to furan itself gave the following inforimation (compared with furan): enhanced negative partial charge at C (2) and c(5), higher acidity at a-positions, a stronger and at the same time inverted dipol moment. In accordance with the calculations, 3,4-DF can easily be substituted by weak electrophilic reagents, e.g. in a typical Mannich reaction. The bis-amino compound 8 is produced in good yields. Lithiation by butyl-Li leads to mono-or di-substituted products. The mono-and di-Li-3,CDF have been used for the preparation of various acylated and alkylated 3,4-DF derivatives.By acid hydrolysis of 3,4-DF crystalline 4-methoxy-3 (2 H)-furanone has been prepared.3,4-Diimethoxyfuran ( = 3,4-DF) wurde von uns gelegentlich zu Reaktionen mit Chinonen und anderen Dienophilen benutzt [3-91. Die dabei zu Tage getretene, gegenuber Furan deutlich erhohte Reaktivitat veranlasste uns, die chemischen und physikalischen Eigenschaften naher zu untersuchen, woruber in dieser und in spateren Arbeiten berichtet werden s0113).

2,5‐Diamide‐Substituted Five‐Membered Heterocycles: Challenging Molecular Synthons

“…Cell parameters were estimated from a pre-experiment run, and full data sets were collected at room temperature. HCl, followed by filtration, washing with H 2 O and azeotropic distillation with toluene), compound 11 [64] (LiOH was used instead of NaOH), compound 15, [65] compound 16, [66] compound 26, [67,69] compound 27, [68,69] and compound 28 [69] (LiOH was used instead of NaOH). [80] Non-hydrogen atoms were anisotropically refined and the hydrogen atoms (not implicated in Hbonds) in the riding mode with isotropic temperature factors fixed at 1.2 times U(eq) of the parent atoms (1.5 times for methyl groups).…”

“…Bader charge analysis was carried out with the program written by Henkelman et al [74,84] Synthetic Procedures: The following compounds were prepared by previously reported procedures, with only slight modifications when specified: compound 9 [64,85] (the sodium salt of the product was protonated by addition of concentrated aq. HCl, followed by filtration, washing with H 2 O and azeotropic distillation with toluene), compound 11 [64] (LiOH was used instead of NaOH), compound 15, [65] compound 16, [66] compound 26, [67,69] compound 27, [68,69] and compound 28 [69] (LiOH was used instead of NaOH).…”

“…[67] Methylation of the hydroxy groups in the β-positions with MeI, [68] followed by saponification with LiOH in THF, [69] yielded compound 28. The synthesis started with the esterification of diglycolic acid by treatment with TMSCl in the presence of MeOH, giving the desired diester 25 in 75 % yield.…”

“…Compound 25 was subsequently condensed with (COOMe) 2 , in the presence of NaH in DMF at 50°C. [67] Methylation of the hydroxy groups in the β-positions with MeI, [68] followed by saponification with LiOH in THF, [69] yielded compound 28. Conversion of the obtained carboxylic acids into acylazides was achieved by the general protocol involving a chlorination step followed by addition of NaN 3 .…”

High‐pressure [2 + 4]‐cycloaddition of dimethylmaleic anhydride to 3,4‐dimethoxyfuran; synthesis of dimethoxycantharidin preliminary communication

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As an active diene (more active than furan itself), 3,4-dimethoxyfuran (1) affords with many dienophiles the respective cycloadducts in a high yield [2]. It has recently been found that under thermal conditions 1 easily reacts with maleic anhydride and its monomethyl derivative, but not with dimethylmaleic anhydride (2) [3].

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