Furan-2,3-diones

NMR data have been recorded for numerous compounds with exocyclic enamine double bonds (79JHC1335). Examples of exocyclic imine double bonds are found in furan-2,3-dione 3-oxime and a related 5-oxime the vie proton coupling constant in the former is 5 Hz and so larger than expected, perhaps because of electron release from the hydroxy oxygen atom (72JCS(P1)2527). 

Variation in the carbonyl component has also been reported. Irradiation of 6-methoxybenzo[b]furan-2,3-dione (391) in the presence of styrene or /i-ethoxystyrene affords adducts 392.339 Other 1,2-dicarbonyl compounds... 

Single-pulse shock-tube thermal decomposition of furonitrile (1135-1380 K) affords primarily but-2-yne 1-nitrile via a radical intermediate.250 Radicals are also implicated in the thermolysis of furan-2,3-dione analogues.251 Explosive-driven shock waves of up... 

Reaction of the furan-2,3-dione 63 with diisopropylcarbodiimide at 25 °C has been reported to give the ring-expanded l,3-oxazepine-6,7-dione 64 in moderate yield (Equation 13) <1997M381>. 

Furan-2,3-diones 779 reacted with various hydrazines to yield pyrazole-3-carboxylic hydrazides 780 in moderate yields (Equation 168) <2005JHC117>. 4-Benzoyl-l-(4-nitrophenyl)-5-phenyl-l//-pyrazole-3-carboxylic acid 782 was obtained from the furan-2,3-dione 781 and A -benzylidene-A -(4-nitrophenyl)hydrazine (Equation 169) <2004CHE1039>. 

In fact the quinones are better known in this series. A general method for the preparation of furan-2,3-diones has been described as outlined in Scheme 46. 79 They have carbonyl bands above 1800 cm 1 in the IR region. 

The cycloaddition of the diene (234) to the furan-2,3-dione derivatives (235) affords the cycloadducts (236). The reaction takes place efficiently with high regio- and stereo-selectivity. 

Addition to the side-chain of the aldimine from 4-anisaldehyde and aniline occurred in its reaction with the furan-2,3-dione shown with toss of carbon monoxide by heating in benzene during 2 hours to give 2-(4-methoxy-phenyl)-3,6-diphenyl-2,3-dihydro-4H-1,3-oxazine-4-one in 93% yield (ref.131)... 

Carbon-13 NMR chemical shifts for a variety of aurones (139) are reported and discussed in order to determine how the substituent effects can be used for structural elucidation <83H2203>. Substituent effects seem not to influence the C chemical shifts of furan-2,3-dione derivatives (140) and (141) <91BSF393>. The modification of the substituent in the para position of the phenyl ring (140) or the strain induced by the bridge (141) do not greatly affect the chemical shifts of the carbon atoms of the furandione ring. 

Phenylurea added to a soln. of startg. furan-2,3-dione in glacial acetic acid, and heated for 1 h - 3-phenyl-5-phenacylideneimidazolidine-2,4-dione. Y 79%. F.e. and 2-thioxo- and 2-selenoxo-analogs from thioureas and selenoureas, respectively, s. Y.S. Andreichikov et al., Khim. Geterotsikl. Soedin. 1988, 1411-3. 

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