Dihydro-4,4-dimethyl-2,3-furandione

Table 11 Asymmetric hydrogenation of dihydro-4,4-dimethyl-2,3-furandione...

The hydrogenation of ketones with O or N functions in the a- or / -position is accomplished by several rhodium compounds [46 a, b, e, g, i, j, m, 56], Many of these examples have been applied in the synthesis of biologically active chiral products [59]. One of the first examples was the asymmetric synthesis of pantothenic acid, a member of the B complex vitamins and an important constituent of coenzyme A. Ojima et al. first described this synthesis in 1978, the most significant step being the enantioselective reduction of a cyclic a-keto ester, dihydro-4,4-dimethyl-2,3-furandione, to D-(-)-pantoyl lactone. A rhodium complex derived from [RhCl(COD)]2 and the chiral pyrrolidino diphosphine, (2S,4S)-N-tert-butoxy-carbonyl-4-diphenylphosphino-2-diphenylphosphinomethyl-pyrrolidine ((S, S) -... 

Among ketoesters, tremendous efforts have been devoted to the hydrogenation of dihydro-4,4-dimethyl-2,3-furandione (KPL), not only as a model reaction but also because the product R(-)-pantolactone is a key intermediate in the synthesis of vitamin B5 and coenzyme A (Scheme 33.1). 

Adedeji et al. (1993) used a direct thermal desorption technique (220°C) to analyse the volatiles from beans that might cause the thermal degradation and transformation of sugar into common volatile compounds such as 3,5-dimethyl-2,4(3H,5H)-furandione and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one. This last compound was detected at a high concentration (3880 ppm) in Mexican vanilla, being the third most abundant compound after vanillin and 2-furfural, and far more abundant than vanillic acid, p-hydroxy-benzaldehyde or p-hydroxybenzoic acid. 

Ketopantoyl lactone 2,3-Furandione, dihydro-4,4-dimethyl (8,9) (13031-04-4) D-(-)-Pantoyl lactone 2(3H)-Furanone, dihydro-3-hydroxy-4,4-dimethyl -,... 

Figure 5.2.10. Cellulose pyrolysate obtained at 59CP C by Py-GC/MS. The separation was done on a Carbowax type column. 1 CO2, 2 acetaldehyde, 3 acetone, 4 2-butanone, 5 2,3-butandione, 6 toluene, 7 water, 8 cyclopentanone, 9 methylfuran, 10 3-hydroxy-2-butanone, 11 hydroxypropanone, 12 cyclopent-1-en-2-one, 13 2-methylcyclopentenone, 14 acetic acid, 15 acetic acid anhydride, 16 furancarboxaldehyde, 17 methylcyclopentenone, 18 dimethylcyclopentenone, 19 5-methylfurancarboxaldehyde, 20 2,3-dihydro-2-furanone, 21 furan-2-methanol, 22 3-methylfuran-2-one, 23 2(5H)-furanone, 24 hydroxycyclopentenone, 25 3,5-dimethylcyclopentan-1,2-dione, 26 2-hydroxy-3-methyl-2-cyclopenten-1-one, 27 2-hydroxy-3-ethyl-2-cyclopenten-1-one, 28 2,3-dimethyl-2-cyclopenten-1-one, 29 phenol, 30 dimethylphenol, 31 3 thyl-2,4(3H,5H)-furandione, 32 3-butenoic acid, 33 1,4 3,6-dianhydro-a-D-glucopyranose, 34 5-(hydroxymethyl)-furfural.

E.65) 2,5-Furandione, 3,4-dimethyl-, 2.5-dihydro-3,4-dimethylfuran-2,5-dione, dimethylmaleic anhydride, dimethyl-2,5-furandione, pyrocinchonic anhydride (766-39-2]... 

Ketopantoyl lactone 2,3-Furandione, d1hydro-4,4-dlmethyl (8,9) (13031-04-4) D-(-)-Pantoyl lactone 2(3H)-Furanone, dihydro-3-hydroxy-4,4-d1methy1 0- (8) 2(3H)-Furanone, d1hydro-3-hydroxy-4,4-dimethyl- (9) (599-04-2) Ch1oro(l,5-cyclooctadiene)rhodium (I) dimer Rhodium, di-v-ch1orobis(l,5-cyclooctadiene) di- (8) Rhodium, di-y-chiorobis[(1,2,5,6- )-l,5-cyclooctadiene] di- (9) (12092-47-6)... 

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