SYNTHESES OF 5,5'-DIFORMYL-2-2'DIFURAN AND DERIVATIVES THEREOF

Abstract: 5,5'-diformyl-2,2'-difuran is prepared in excellent yield by photochemically irradiating furfural or a mixture of furfural and 5-bromo-2-furfural. In the latter case an acid scavenger is present. The solvent is acetonitrile. The process may be carried out continuously, the 5-bromo-2-furfural acting as a catalyst, the furfural being added, and the product being harvested continuously.

Description: SYNTHESES OF 5,5'-DIFORMYL-2,2'DIFURAN AND DERIVATIVES THEREOF TECHNICAL FIELD OF THE INVENTION This invention relates to the synthesis of 5,5'-diformyl-2,2'-difuran and derivatives thereof, as well as to the derivatives themselves as new chemical compounds. BACKGROUND OF THE INVENTION Difunctional aromatic monomers have vast potential and uses in the polymer industry and are presently used in many applications. Present technology to produce difunctional monomers through two base nuclei from the single nucleus has been achieved utilising a metal halide intermediate. This technology has the disadvantage of requiring an initial halogenation step after which the halogenated nuclei are treated with a metal powder. High temperatures, long reaction time and laborious work-up procedures followed by low yields make this process uneconomical. Industrially the large quantities of metal powder required make this process extremely difficult to handle on a large scale, whilst the specific metal required must be chosen with care as to prevent conversion of the parent functional group to another functionality. Presently industry is dominated by difunctional phenyl derivatives through either one or two base nuclei. No difunctional furan derivatives through two base nuclei are presently synthesised on an industrial scale. Considering 5,5'diformyl-2,2'difuran it has been found that this compound has been synthesised through an Ullmann condensation utilising 5-iodo-2-furaldehyde, palladium catalysed coupling of 2-furaldehyde, or via the photolytic dimerisation of 5-bromo-2-furfural. The reported syntheses of the target compound involve laborious preparation of the starting materials, numerous work-up steps, high cost and low yields. It is an object of the present invention to prepare 5,5'-diformyl-2,2'-difuran and derivatives thereof in good yield and purity, and to avoid the use of high temperatures, solid metal powders and tedious work-up procedures. DISCLOSURE OF THE INVENTION According to the invention a method of synthesising 5,5'-diformyl-2,2'-difuran and derivatives thereof includes the step of photochemically irradiating furfural with 5-bromo-2-furfural in the presence of a suitable acid scavenger; or with 5.5'-diformyl-2,2'-difuran and derivatives thereof with or without an acid scavenger, and recovering the 5,5'-diformyl-2,2'-difuran and derivatives thereof from the reaction mixture. In a preferred form of the invention the acid scavenger is polyvinyl pyridine but it is expected that other acid scavengers may also be useful. The solvent for the reactants is preferably acetonitrile but it is expected that other solvents may also be useful. However, petroleum ether, hexane, and dicholoromethane were found to give inferior yields. A yield of 87 percent has been obtained using acetonitrile as solvent. The reaction mixture should be freed of oxygen prior to the photochemical irradiation and this may conveniently be achieved by purging it with nitrogen. A UV lamp of wavelengths of the order of 200-400 nm may be used for the irradiation step. It has been found that the 5-bromo-2 -furfural may be used in very small or catalytic quantities. It has also been found that once sufficient 5,5'-difoιmyl-2,2'-difuran is in solution the reaction proceeds without further addition of 5-bromo-2-furfural and the process can be made continuous by constant addition of furfural and harvesting the precipitated 5,5'-diformyl-2,2'-difuran. EXAMPLE 5-bromo-2-furfural (1) (0.181G, 1.04mmol) and furfural (2) 2.0g, 20.8mmol) dissolved in acetonitrile (400ml) contained in a quartz flask was treated with activated polyvinyl pyridine (0,4g, 25mmol). The solution was purged with nitrogen for 15 5 minutes and then irradiated with a UV lamp (400w medium to high pressure mercury lamp) for 25h. The solution was treated with charcoal (ca. 2g) and warmed at 75°C with stirring for 5 minutes, filtered hot, concentrated under reduced pressure to a small volume (ca. 20ml) and cooled to 0°C for 20 minutes to afford pure 5,5'diformyl-2,2'-difuran product or the reacted mixture was poured into an excess ot diethyl ether resulting in rapid 10 precipitation of 5,5'diformyl-2,2'-difuran (3) in quantitative yield. In another example of the invention the reacted solution is led to a holding tank where a degree of crystallisation occurs. This is then passed to a filter for removal of the crystals and then supernatant liquid is returned to the irradiation zone. Unreacted liquid may be fed to the irradiation zone or to the holding tank to maintain a predetermined •j r volume of liquid in the continuous system. A rough flowsheet follows: In the flowsheet, a continuous system is shown comprising a UV lamp (10) surrounded by a sleeve (12) for the furfural and 5-bromo-2-furfural solution to pass and be irradiated. The irradiated liquid passes into a holding tank (14) from which it is withdrawn at low level (16). From there it is passed to a filtering station comprising alternative filters (18) controlled by valves (20). The supernatant liquid is returned to the irradiation zone. Unreacted solution and additional raw feed material may be added at 22 or 24 to maintain a predetermined volume of reactants in the system whilst 5,5'diformyl-2,2' difuran is continuous harvested (filtered) from the reaction mixture at the filter station. The diformyl compound may be converted by ordinary chemical routes to various derivatives, of which the following have been prepared. R" = R 6 = C0 2 H; R 2 =R 3 =R 4 =R 5 = H : 5,5' Dicarboxylic acid -2,2'-difuran (m.p>300°C). R 1 = R 6 = CH 2 OH; R 2 =R =R 4 =R 5 = H : 5,5' -Dimethylacohol-2,2'-difuran m.p.l36°C). R 1 = R 6 = CH=CH-C-Ph; R 2 =R 3 =R =R 5 = H: where Ph = phenyl Bis-5,5'-(3-oxo-3-phenyl-l-propenyl-2,2'difuran (m.p. 232°C). 0 l| R 1 = R 6 = CH=CH-C-CH 3 ; R 2 =R 3 R 4 =R 5 = H: 5,5'-di(but-l-ene-3-one)-2,2'difuran (m.p. 168°C). R 1 = R 6 = CH=N-Ph; R 2 =R 3 =R 4 =R 5 = H : 5 - Formyl-5'-N-phenylmethylene-2,2'-difuran. 0 II R 1 = R 6 = C-NH 2 ; R 2 =R =R =R 5 = H : 5,5'-Diamido - 2,2'-difuran (m.p. 180°C). R 1 = R 6 = CH 2 NH 2 ; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Diaminomethyl-2,2'-difuran R 1 = R 6 = CH=CH 2 ; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Divinyl-2,2'-difuran. R 1 = R 6 = CH-CH; R 2 =R 3 =R 4 =R 5 = H : 5 ,5 ' -Dioxiranyl-2,2 ' -difuran. R 1 = R 6 = CH=N0H; R 2 =R 3 =R 4 =R 5 H : 5,5 ' -(Dioxime)-2,2 ' -difuran. R 1 = R 6 = C = N, R 2 =R 3 =R 4 =R 5 = H 5,5'Dinitrilo-2,2'-difuran. R 1 = R 6 = CH(0Ac) 2 ; R 2 =R =R 4 =R 5 = H 5,5'-Bis(diacetate)-2,2'-difuran m.p. 153-154°C. R 1 = R 6 = CH = CHN0 2 ; R 2 =R 3 =R 4 =R 5 = H 5,5' -Di(nitro vinyl)-2,2 ' difuran. R' = R 6 = CH = CHC0 2 H; R 2 =R 3 =R 4 =R 5 = H 5,5'-Diacrylic acid-2,2' -difuran.

Claims: CLAIMS: 1. A method of synthesising 5,5'-diformyl-2,2'-difuran and derivatives thereof characterised in that furfural or a derivative thereof is subjected to photochemical irradiation with itself or a substance capable of reacting or condensing therewith. 2. The method according to claim 1 characterised in that furfural or a derivative thereof is irradiated with a corresponding halogenated furfural in the presence of an acid scavenger. 3. The method according to claim 2 characterised in that furfural is irradiated photochemically with 5-bromo-2-furfural. 4. The method according to claim 2 or claim 3 characterised in that the halogenated furfural is used in catalytic quantities. 5. The method according to claim 4 characterised in that the reaction proceeds continuously by constantly adding furfural and harvesting the precipitated 5,5'-diformyl-2,2'-difuran. 6. The method according to any of claims 2 to 4 characterised in that the acid scavenger is polyvinyl pyridine. 7. The method according to any of the above claims characterised in that the photochemical irradiation is carried out in acetonitrile as solvent. 8. The method according to any of the above claims characterised in that the reaction mixture is purged of oxygen prior to photochemical irradiation. 9. The method according to any of the above claims characterised in that a UV lamp of 200-400 nm is used for the irradiation step. 10. The method according to any of the above claims characterised in that the following products are prepared: R < R J n l R~ R 1 = R 6 = C0 2 H; R =R 3 =R =R 5 = H : 5,5' Dicarboxylic acid -2,2'-difuran (m.p>300°C). R 1 = R 6 = CH 2 OH; R 2 =R 3 =R =R 5 = H : 5,5' -Dimethylacohol-2,2'-difuran m.p.l36°C). 0 II R' = R 6 = CH=CH-C-Ph; R 2 =R 3 =R 4 =R 5 = H: where Ph = phenyl Bis-5,5'-(3-oxo-3-phenyl-l-propenyl-2,2'difuran (m.p. 232°C). 0 II R 1 = R 6 = CH=CH-C-CH 3 ; R 2 =R 3 R 4 =R 5 = H: 5,5'-di(but-l-ene-3-one)-2,2'difuran (m.p. 168°C). R 1 = R 6 = CH=N-Ph; R 2 =R 3 =R 4 =R 5 = H : 5 - Formyl-5'-N-phenylmethylene-2,2'-difuran. 0 II R i = R = C-NH 2 ; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Diamido - 2,2'-difuran (m.p. 180°C). R' = R 5 = CH 2 NH 2 ; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Diaminomethyl-2,2'-difuran R 1 = R 6 = CH=CH 2 ; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Divinyl-2,2'-difuran. R 1 = R 6 = CH-CH; R 2 =R 3 =R 4 =R 5 = H : 5,5'-Dioxiranyl-2,2'-difuran. R 1 = R 6 = CH=N0H; R 2 =R 3 =R 4 =R 5 H : 5,5 ' -(Dioxime)-2,2' -difuran. R 1 = R 6 = C = N, R 2 =R 3 =R 4 =R 5 = H 5,5'Dinitrilo-2,2'-difuran. R' = R 6 = CH(0Ac) 2 ; R 2 =R 3 =R 4 =R 5 = H 5,5'-Bis(diacetate)-2,2'-difuran m.p. 153-154°C. R 1 = R 6 = CH = CHN0 2 ; R 2 =R 3 =R 4 =R 5 = H 5,5'-Di(nitrovinyl)-2,2'difuran. R l = R 6 = CH = CHC0 2 H; R 2 =R 3 =R 4 =R 5 = H 5,5'-Diacrylic acid-2,2' -difuran. 11. Apparatus for carrying out the method according to any of the above claims characterised by a UV lamp surrounded by a sleeve for the reactant/s to be irradiated, means to pass the irradiated product into a holding tank have an outlet at a low level leading to a filtering station. 12. Apparatus according to claim 11 further including means to return the supernatant liquid to the irradiation zone for unreacted substances and additional raw feed material to maintain a predetermined volume of reactants while the final product is harvested.

Inventors: BURGER GREGORY JAMES, WILLS ALAN DOUGLAS, BURGER, GREGORY, JAMES, WILLS, ALAN, DOUGLAS
Applicants: BURGER GREGORY JAMES, WILLS ALAN DOUGLAS, BURGER, GREGORY, JAMES, WILLS, ALAN, DOUGLAS
Application year: 1999
Main classification: C07D307
IPC codes: B01J31, B01J35, C07D307, C07D407