Furans 2,5-dihydro-2-methylene

Furan, 2,3-dihydro-5-methyl-polymers, 1, 276 Furan, 2,3-dihydro-3-methylene- H NMR, 4, 577 Furan, 2,5-dihydro-2-methylene- H NMR, 4, 577 tautomerism aromaticity and, 4, 595 Furan, 2,5-dihydro-2-nitro-structure, 4, 550 Furan, 2,3-dihydroxy-tautomerism, 4, 37 Furan, 2,4-dihydroxy-tautomerism, 4, 37 Furan, 3,4-dihydroxy-tautomerism, 4, 37 Furan, 2,5-diiodo-nitration, 4, 602 synthesis, 4, 712 Furan, 3,4-diiodo-reactions, 4, 650 Furan, 2,3-dimethoxy-synthesis, 4, 625, 648 Furan, 2,5-dimethoxy-synthesis, 4, 648 Furan, 3,4-dimethoxy-cycloaddition reactions, 4, 64, 625 lithiation, 4, 651 reactions... 

Furan, 2>3-dihydro-5-methyl-polymers, 1, 276 Furan, 2,3-dihydro-3-methylene- H NMR, 4, 577 Furan, 2,5-dihydro-2-methylene- H NMR, 4, 577 tautomerism... 

D) Preparation of 2-(1-Hydroxyethyi)-3-Methyi-5-(2-Oxo-2,5-Dihydro-4-Furyi)Benzo[b] Furan (3574 CB) 13,2 grams of compound 3556 CB of which the preparation is described in (C) are treated successively with 66 ml of methylene chloride, 27 ml of methanol and, with stirring, 1.6 grams of sodium borohydride added in stages. The reaciton takes 1 hour. The mixture is poured into water acidified with a sufficient amount of acetic acid, the solvents are stripped under vacuum, the crystalline product removed, washed with water, and recrystallized from ethyl acetate. Yield 90%. MP <=158°C. 

Of particular interest was the carbonylation of (Z)-2-en-4-yn-l-ols and (Z)-(2-en-4-ynyl)amines, which afforded furan-2-acetic [104,105] and pyrrole-2-acetic [116] esters, respectively, in good yields, through spontaneous or acid-promoted aromatization of the initially formed ( )-2-(alkoxycarbonyl)-methylene-2,5-dihydro-furans or -pyrroles (Scheme 31). 

Raney nickel reduction of 2-benzyl-5-ethylselenophene (71) yields 1-phenylheptane (72), a conversion analogous to the much used reductive desulfurization of thiophenes (73JGU871). The electrochemical reduction of selenophene-2-carboxylic acid gives a mixture of dimeric products the major product is compound (73). This is in contrast to the 2,5-dihydro derivatives obtained by electrochemical reduction of thiophene and furan carboxylic acids (82CS( 19)95). Wolff-Kishner reduction of 2-selenienyl 2 -thienyl ketone gives, in addition to the expected methylene derivative, 2-(pentenyl)thiophene (72ZOB1780). 

Kalium- 2-Alken- E14b, 817 (02N —en-amin + —CH2 —) Kalium-5-methylen-2,5-dihydro-furan-2- E6a, 124 (2-N02 4- KOR/R2CH2) Lithium- Alkan- E14b, 806 (aus R —N02)... 

Furan 3-Lithio-4-methoxy-5-methylen-2-oxo-2,5-dihydro-E19d, 192 (H - Li)... 

Furan-2-nitronat Kalium-5-(dicyan-methylen)-2,5-dihydro- E6a, 124 [2,5-(N02)2 —furan +... 

Furan 2-Aminomethyl-5-(2,4-dioxo-1,2,3,4-tetrahydro-pyrimidino)-2,5-dihydro- IV/lc, 578 Imidazo(l,2-a]pyridin 1,5-Dimethyl-8-nitro-7-oxo-l,2,3,7-tetrahydro-E15/3, 2790 [cycl. (R2N)2C = CH-N02 4- Diketen] 1,3-Oxazol 4-Cyan-5-(diethoxy-methylen-amino)- E4, 565 (Het — NH2 + Orthoester) Pyrazin 3-Amino-2-methoxycarbo-nyl-5-propanoyl- E9b/2, 324 (H - CO-R)... 

The rDA cycloieversitHi of a protected butadiene adduct has been applied to the synthesis of unsaturated oxygen heterocycles. The very unstable 2,3-dihydro-2,3-bis(methylene)furan and its 4-methyl derivative have been generated by rDA reaction of 4,5,6,7-tetrahydrobenzofuran and its dimethylated derivative (equation 82). Characterization of these dienes was accomplished by trapping with various dienophiles. This method was extended to a two-step rDA synthesis of tetramethylenetetrahydrofuran as shown in equatirai (83). ... 

Fig. 16. Chemical structures for Ras inhibitors, (a) GTP analogs with modified bases bind to Ras with up to a Kiel (IC50 of Analog divided by the IC50 of GDP) of 3.30. (b) Sulindac sulfide ((3Z)-3-(4-(methylthio)benzylidene)-6-fluoro-3,3a-dihydro-2-methyl-2H-indene-1 -carboxylic acid) disrupts this interaction with an IC50 of approximately 210 pM. (c) An optimized sulindac analog ((3Z)-6-fluoro-3-((furan-3-yl)methylene)-3,3a-dihydro-2-methyl-2H-indene-1 -carboxylic acid) has an IC50 of approximately 30 pM. The molecular basis of the compound s mechanism of action is unknown, but both (b) and (c) are hypothesized to operate by disrupting Ras-Raf interactions.

Acyl-2-(anilmo-methylen)-3-oxo-2,3-dihydro-furane geben lH-Pyrazole, wenn das Anilino-N-Atom acetyliert ist1585 ... 

Als Enol-ether von 1,3-Dicarbonyl-Verbindungen und 3-Oxo-alkansaure-estern reagieren 5-Aryl-2-(ethoxycarbonyl-methylen)-4-methyl-3-oxo-2,3-dihydro-furane mil 70%iger Hy-drazin-Hydrat-Losung zu 3(5),3 (5 )-Bi-lH-pyrazolylen988. 

Weitere Beispiclc sind aus der Reihe der Heterocyclen bekannt. So liefert 5-Oxo-2-methylen-2,5-dihydro-furaii (Protoanemonin IX) beim Belichten in Methanol (-50°, Quecksilber-Hochdruck-Lampc) 5-Oxo-2,5-dihydro-furan-(2-apiro-iy-cydohu,tan-(2-spiro-2 -5-oxo-2,5-dihydro-furan (Anemonin X 75%), welches auch durch thermische [2 4-2 -Dimensioning bci 20° entsteht4 ... 

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