2- Furanyl ketones

An extension of the Barbier reaction to carboxylates salts [90] affords a simple access to furanyl ketones [91]. By sonication of a mixture of a lithium carboxylate, an alkyl chloride and lithium in THE at room temperature, the intermediate organolithium reagent forms rapidly, then generates the 2-furanyl lithium which adds to the carboxylate group in high yields. The method constitutes an example of a reaction cascade , in which several intermediates are generated sequentially (Scheme 3.13). 

CARDIVIX CAROFAM CORONAL-CRINOS 3,5-DIIODO-4-HYDROXYPHENYL 2-ETHYL-3-BENZO-FURANYL KETONE DILAFURANE DILA-VASAL KETONE, 3,5-DIIODO-4-HYDROXYPHENYL 2-ETHYL-3-BENZOFURANYL L 2329 2329 LABAZ RETRANGOR... 

The enolate anions of 2-acetylthiophene and 2-acetylfuran have been arylated under photochemical conditions in the presence of t-BuOK and good electron donors such as acetone enolate (entrainment reaction) to give the corresponding benzyl 2-thienyl and 2-furanyl ketones respectively. Use of FeBr2 as initiator in a dark reaction gives good yields of the substitution products without the need for added nucleophiles, and it is suggested that these arylation processes occur by an SrnI mechanism. 

Acylfurans 2- and 3-Acylfurans can be prepared in excellent yield by reaction of furoyl chlorides with RMnCl catalyzed by CuCl. This reaction can provide the natural furanyl ketones naginata ketone (I) and perilla ketone (2). 

Another route to these furanyl ketones involves acylation of furylmangancse chloride catalyzed by iron(lll) acctylacctonatc (equation l). 

Ketones. Sonochemical Barbier reaction allows direct access to ketones from the condensation of lithium carboxylates and organohalides in the presence of Li. An interesting approach to 2-furanyl ketones involves in situ deprotonation of furan with nascent t-BuLi (generated with the assistance of ultrasound) and subsequent reaction with RCOOLi. 

Primary alkyl chlorides generally form ketones in satisfactory yields, but from secondary and tertiary compounds, deprotonation is much faster than addition, and the ketone yields are too low for practical interest. Based on the deprotonation reaction, especially important with f-butyl chloride, a preparation of 2-furanyl ketones resulting from a reaction cascade was found (Fig. 

The reaction of an allene with an aryl- or vinylpalladium(II) species is a widely used way of forming a Jt-allyl complex. Subsequent nucleophilic attack on this intermediate gives the product and palladium(O) (Scheme 17.1). Oxidative addition of palladium ) to an aryl or vinyl halide closes the catalytic cycle that does not involve an overall oxidation. a-Allenyl acids 27, however, react with palladium(II) instead of with palladium(O) to afford cr-vinylpalladium(II) intermediates 28 (Scheme 17.12). These cr-complexes than react with either an allenyl ketone [11] or with another alle-nyl acid [12] to form 4-(3 -furanyl)butenolides 30 or -dibutenolides 32, respectively. 

The involvement of transition-metal allenylidene complexes in homogeneous catalysis was reported for the first time by B. M. Trost and co-workers in 1992 (Scheme 35) [293-295]. The catalytic reactions allowed the preparation of a wide variety of tetrahydropyranyl and furanyl p,y-unsaturated ketones starting from hydroxy-functionalized alkynols and allylic alcohols, the key step in the catalytic... 

Kinetic and thermodynamic measurements show that 2-phenylacetylthiophene (92a) has a low enol content K = 3.55 x 10 7 (or )K = 6.45).136 The keto and enol tautomers have pKa values of 14.60 and 8.15, respectively. Relative to a phenyl or furanyl substituent at the carbonyl carbon, the thiophene increases the acidity of the enol tautomer, but stabilizes the ketone, probably via the resonance contribution (92b). Thus 2-thiophenyl stabilizes the enolate by electron attraction, but the ketone by donation. Effects of micelles on the equilibria are also reported. 

Cyclopropanation of furanyl diazo ketones. The reaction of a-diazo ketones of furanylpropionic acids with Rh2(OAc)4 involves formation of an unstable cyclo-... 

Allenyl ketones can also be cross-coupled with allenoic acids to give 2,4-disubstituted furans <2002AGE1775> or with allenamides to yield 4-(3 -furanyl)-2(5//)-furanimines <2005JOC6291>. With chiral allenoic acid derivatives, 4-(3 -furanybbutenolides can be synthesized stereoselectively with complete chirality transfer (Equation 47) <2004CEJ2078>. 

Isomerization of an a-allenylcyclopentenone, obtained from a propargyl ether and a mopholino a,p-unsaturated amide, in the presence of Hg-catalyst to a furanyl cyclopentenone provided another example of the conversion of allenyl ketones to furans <03OLl 171>. 

SYNS (-)-BOTRYODIPLODIN 2-HYDROXY-3-METHYL-4-ACETYLTETRAHYDROFURANE METHYL TETRAHYDRO-5-HYDROXY-4-METHYL-3-FURYL KETONE l-(TETRAHYDRO-5-HYDROXY-4-METHYL-3-FURANYL)-ETHANONE (9CI)... 

SYNS ETHANONE, l-(2-ETHYL-7-(2-HYDROXY-3-((l-METHYLETHYL)AMINO)PROPOXY)-4-BENZO-FURANYL)- 2-ETHYL-4-ACETYL-7-(2-HYDROXY-3-ISOPROPYLAMINOPROPOXY)BENZOFURAN KETONE, 2-ETHYL-7-(2-HYDROXY-3-(ISOPROPYL-AMINO)PROPOXY)-4-BENZOFURANYL METHYL... 

SYNS l-(3-FURANYL)-4-METHYL-l-PENTANONE D P-FURYL ISOAMYL KETONE D l-(3-FURYL)-4-METHYL-1-PaNTANONE PURPLE MINT PLANT EXTRACT... 

The yeast-induced reduction of (5e) —> (6e), (R = substituted phenyls, R = Me) is one of the very first preparative-scale alcohol dehydrogenase catalyzed reactions to have been reported. While the transformations of (5a-j) demonstrate that broad structural mlerances are possible in the substrate ketones, the enzymes are sometimes very discriminating. For example, while the BY-catalyzed reductions of the 2-, 3- and 4-substituted pyridyl ketones (5g) proceed smoothly with high stereospecificitythe analogous furanyl and thiophenyl ketones give virtually racemic product alcohols, and 2-acetylpyrrole is not a substrate at all. ... 

Ethanone, l-(2-furanyl)-, l-(2-furyl) ethan-l-one, 2-furyl methyl ketone, 2-acetylfuran [1192-62-7] FEMA 3163... 

Propanone, l-(5-methyl-2-furanyl)-, l-(5-methyl-2-furyl)propan-l-one, ethyl 5-methyl-2-furyl ketone, 2-methyl-5-propanoylfuran, 2-propionyl-5-methylfuran [10599-69-6]... 

Euparin, I-[6-Hydroxy-2-11-tnethyiethenyl)-5-benzofu ranyljethanone 6-hydroxy-2-isopropenyl-5-benzo furanyl methyl ketone 5 -acetyl -6-hydroxy -2-isopropenyJ -benzofuran, Cl3Hl2Oj mol wt 216,23. C 72.21%, H 5.59%, O 22.20%, From roots of Eupatorium purpureum L., E. cannabinum L., Compositae Kamthong, Robertson, J. 

Perilla Ketone. l-(3-Furanyl)-4-methyl-l-penta-none l-(3-furyl)-4-meihyl-l-pentanone 0-turyl isoamyt ketone. C HmO, mol wt 166.22. C 72.26%. H 8.49%. O 19.25%. Potent pulmonary edcmatogenjc agent in animals. Isoln from the mint plant, Perilla fruteseens Britton, Labi-atae, and structure R. Goto, J. Pharm. Soc. Japan 57, 77 (1937). Synthesis T. Matsuura, Bull Chem. Soc, Japan 30, 430 (1957) K. Rondo, M. Matsumoto, Tetrahedron Letters 1976, 4363 T. Kitamura et of., Synth. Common. 7, 521 (1977) K. Inomata et al, Chem. Letters 1979, 709. Potent lung toxin implicated in emphysema of grazing cattle B. I. Wilson et al. Science 197, 573 (1977). 

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