Dihydro-5- -furanone

O-Heterocycles Furfural 2-Furanylethanone Furanmethanolacetate MARM ++ Hydroxymethylfurfural 2-MethyItetra (or dihydro) furanone 5-MethyI-2-furfural 2-Furanmethanol 2-Furan methanol (Fume) (RV = 0.995)... 

SL179,94JOC67). These compounds are valuable precursors for the preparation of 3(2f0 dihydro-furanones. 

These trivial names are permitted -y-butyrolactone, -y-valerolactone, and 5-valerolactone. Names based on heterocycles may be used for all lactones. Thus, -y-butyrolactone is also tetrahydro-2-furanone or dihydro-2(3/f)-furanone. 

Butyrolactone. y-Butyrolactone [96-48-0] dihydro-2(3H)-furanone, was fkst synthesized in 1884 via internal esterification of 4-hydroxybutyric acid (146). In 1991 the principal commercial source of this material is dehydrogenation of butanediol. Manufacture by hydrogenation of maleic anhydride (147) was discontinued in the early 1980s and resumed in the late 1980s. Physical properties are Hsted in Table 4. 

Benzo[b]furan-4(5H)-one, 6,7-dihydro-synthesis, 4, 710 Benzofuranones H NMR, 4, 579 Benzo[b]furanones from 3-hydroxyflavanone, 3, 729 Benzo[b]furan-2(3H)-ones — see 2-Coumaranones Benzo[b]furan-3(2H)-ones IR spectra, 4, 590 reactions, 4, 650 Benzo[ c]furan-1 (3 W) -ones carbanions, 4, 579 H NMR, 4, 579 reactions with arynes, 1, 415 structure, 4, 552... 

Dodecyloxy-3-(2-chloroethyl)-2-methyl-4//-pyrido[l,2-n]pyrimidin-4-one 317 was obtained by cyclization of 3- l-[(3-dodecyloxy-2-pyridyl)ami-no]ethylidene -4,5-dihydro-2(3//)-furanone (316) in boiling POCI3 (95MIP4). 

Similarly, (A )-( )-3-(2-methoxymethyl-l-pyrrolidinyl)-l-phenylpropene118 121, after lithia-tion and addition of acetone, acidic hydrolysis and oxidation of the intermediate lactol, gives (5)-dihydro-5,5-dimethyl-4-phenyl-2(3/f)-furanone with 98% ee and 54% overall yield. Thus, these sequences constitute asymmetric homoaldol addition. 

Optically active dihydro-2-methylene-2(3//)-furanones fused to 5- and 6-membered carbocyclic rings were synthesized with 64-92% ee using the intramolecular reaction between chiral 2-alkoxy-carbonylallylsilanes and aldehydes80. 

S)-Dihydro-3-methylene-5-(2-methylpropyl)-2(3//)-furanone Typical Procedure9 ... 

S-[3-terl-buto.xycarh 61% d.r. iantijsyn) >70 30... 

Poorer diastereoselection occured in the case of the 3-substituted dihydro-2(3//)-furanones when lithium and copper(I) enolates were employed. 

The photo [2 + 2] reaction between 5-methyl-2,3-dihydro-3-furanone (80) and methyl P-acetoxyacrylate (81) afforded a mixture of four adducts, from which the lactone (82) was isolated. The lactone (82) was reduced to the alcohol (53), which would rearrange quantitatively to the lactone aldehyde (84) upon treatment with... 

Bromo-2-propenyl)-4-methyl-y-butyrolactone 2(3H)-Furanone, 5-(2-bromo-2-propenyl)dihydro-5-methyl- (13) (138416-14-5)... 

Thermolysis of D-fructose in acid solution provides 11 and 2-(2-hydrox-yacetyl)furan (44) as major products. Earlier work had established the presence of 44 in the product mixtures obtained after acid-catalyzed dehydrations of D-glucose and sucrose. Eleven other products were identified in the D-fructose reaction-mixture, including formic acid, acetic acid, 2-furaldehyde, levulinic acid, 2-acetyl-3-hydroxyfuran (isomaltol), and 4-hydroxy-2-(hydroxymethyl)-5-methyl-3(2//)-furanone (59). Acetic acid and formic acid can be formed by an acid-catalyzed decomposition of 2-acetyl-3-hydroxyfuran, whereas levulinic acid is a degradation prod-uct of 11. 2,3-Dihydro-3,5-dihydroxy-6-methyl-4//-pyran-4-one has also been isolated after acid treatment of D-fructose.The pyranone is a dehydration product of the pyranose form of l-deoxy-D-eo f o-2,3-hexodiulose. In aqueous acid seems to be the major reaction product of the pyranone. 

The natural products as- and fra t-whisky lactones 95 have been prepared from the furanones 94 (92-93% yield), which were themselves obtained from ak-3-phenyl-6-butyl-3,6-dihydro-l,2-dioxin 92 and a chiral malonate ester 93 in 54% yield <20060L463> chromatographic separation on silica gel provided the pure (3R,43, 53)- and (33, 4i ,5R)-diastereomers of 94 which were converted into two nature-identical and two non-natural isomers of 95. 

In smog chamber studies of the oxidation of 1-decene, octanal was the condensed-phase product formed in the next highest yield after nonanal, nonanoic acid, and dihydro-5-pentyl-2(3//)furanone (Forstner et al., 1997a). Write a plausible mechanism for its formation. 

The assignment of (/ )-2,3-dihydro-2-phenylfuran rests on Jones oxidation which furnished (ft)-dihydro-5-phenyl-2(3//)-furanone [(/ )-24]80. The configuration of the corresponding S-enantiomer (obtained by yeast reduction of 4-oxo-4-phenylbutanoic acid) was established by correlation with ethyl (S)-3-hydroxy-3-phenylpropanoate (of known configuration, obtained itself by a baker s yeast reduction) by a sequence featuring an Arndt -Eistert homologization as the key step (see also p 403)19. 

The conversion of (4S,5S)-dihydro-5-[(S)-l-hydroxyethyl]-4-trimethylsilyl-2(3//)-furanone (7, see p 416) into the (Z)-alkene 8 served to establish the relative configuration at C-4 and C-5 in 7 on the basis of the established double bond configuration in 8 and the anticipated (anti) stereochemistry of the elimination reaction (see also p474)81. 

R,5R)-5-[(lR)-l-benzyloxy-2-propenyl -dihydro-3-methyl-2(3H)-furanone 15 ( S,5R )-5- (/R )-t-benzyloxy-2-propenyf -dihydro-3-methyl-2(3 )-furanone... 

Either enantiomer of a-alkylated alkanoic acids, 3-substituted dihydro-2(3//)-furanones and 3-substituted tetrahydro-2//-pyran-2-ones with known absolute configuration and high optical purities can be obtained from metalation and alkylation of chiral 4,5-dihydrooxazoles (see Section 1.1.1.4.3.). 

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