Furans ketones

Behavioral observations of male white-tailed deer indicate that urine could play a role in olfactory communication in this animal [131]. To extend the knowledge of the urinary volatiles of the white-tailed deer and to investigate the possibility that vaginal mucus could also carry semiochemical information, Jemiolo et al. [132] studied the qualitative and concentration changes in the profiles of the volatiles present in these excretions. Forty-four volatiles were found in the mucus and 63 in female urine. The volatiles common to both vaginal mucus and urine included alcohols, aldehydes, furans, ketones, alkanes, and alkenes. Aromatic hydrocarbons were found only in the mucus, whereas pyrans, amines, esters and phenols were found only in the urine. Both estrous mucus and estrous urine could be identified by the presence of specific compounds that were not present in mid-cycle samples. Numerous compounds exhibited dependency on ovarian hormones. 

Organomanganese reagents allow preparation of 2- and 3-acylfurans, under mild conditions, in excellent yields. In this way, miscellaneous natural furanic ketones were efficiently synthesized (Scheme 13.20) [18]. Organomanganese... 

The oxidation of the cyclic enol ether 93 in MeOH affords the methyl ester 95 by hydrolysis of the ketene acetal 94 formed initially by regioselective attack of the methoxy group at the anomeric carbon, rather than the a-alkoxy ketone[35]. Similarly, the double bond of the furan part in khellin (96) is converted ino the ester 98 via the ketene acetal 97[l23],... 

Pd(II) salts promote the carbonylation of organomercury compounds. Reaction of phenylmercury chloride and PdCh under CO pressure affords benzophenone (429)[387]. Both esters and ketones are obtained by the carbonylation of furylmercury(Il) chloride in alcohol[388]. Although the yields are not satisfactory, esters are obtained by the carbonylation of aryl- and alkylmercuryfll) chlorides[389,390]. One-pot catalytic carbonylation of thiophene, furan, and pyrrole (430) takes place at the 2-position via mercuration and transmetallation by the use of PdCb, Hg(N03), and CuCl2[391]. 

The 4-kcto group in the alkyne 262 as an enol form adds to the triple bond to give the furan 263[133], Even the conjugated keto alkyne 264 was converted into the furan 266 via isomerization to the allenyl ketone 265[134],... 

Electron-deficient alkenes add stereospecifically to 4-hydroxy-THISs with formation of endo-cycloadducts. Only with methylvinyl-ketone considerable amounts of the exo isomer are produced (Scheme 8) (16). The adducts (6) may extrude hydrogen sulfide on heating with methoxide producing 2-pyridones. The base is unnecessary with fumaronitrile adducts. The alternative elimination of isocyanate Or sulfur may be controlled using 7 as the dipolarenOphile. The cycloaddition produces two products, 8a (R = H, R = COOMe) and 8b (R = COOMe, R =H) (Scheme 9) (17). Pyrolysis of 8b leads to extrusion of furan and isocyanate to give a thiophene. The alternative S-elimi-nation can be effected by oxidation of the adduct and subsequent pyrolysis. 

Diketones are readily transformed to cycHc derivatives, such as cyclopentanones and furans. In this manner, the fragrance dihydrojasmone (3-meth5l-2-pentyl-2-cyclopenten-l-one) is prepared by the base-catalyzed aldol condensation of 2,5-undecanedione. 2,5-Undecanedione is itself prepared from heptanal and methyl vinyl ketone in the presence of thiazoHum salts (329). i7j -Jasmone can be similarly prepared (330,331). 

Transformation of pyridazine 1-oxides and their methyl derivatives into cyclopropyl ketones and/or substituted furans can also occur (Scheme 14). 

A-Substituted pyrroles, furans and dialkylthiophenes undergo photosensitized [2 + 2] cycloaddition reactions with carbonyl compounds to give oxetanes. This is illustrated by the addition of furan and benzophenone to give the oxetane (138). The photochemical reaction of pyrroles with aliphatic aldehydes and ketones results in the regiospecific formation of 3-(l-hydroxyalkyl)pyrroles (e.g. 139). The intermediate oxetane undergoes rearrangement under the reaction conditions (79JOC2949). 

The dianions derived from furan- and thiophene-carboxylic acids by deprotonation with LDA have been reacted with various electrophiles (Scheme 64). The oxygen dianions reacted efficiently with aldehydes and ketones but not so efficiently with alkyl halides or epoxides. The sulfur dianions reacted with allyl bromide, a reaction which failed in the case of the dianions derived from furancarboxylic acids, and are therefore judged to be the softer nucleophiles (81JCS(Pl)1125,80TL505l). 

Acyl-pyrroles, -furans and -thiophenes in general have a similar pattern of reactivity to benzenoid ketones. Acyl groups in 2,5-disubstituted derivatives are sometimes displaced during the course of electrophilic substitution reactions. iV-Alkyl-2-acylpyrroles are converted by strong anhydrous acid to A-alkyl-3-acylpyrroles. Similar treatment of N-unsubstituted 2- or 3-acyIpyrroles yields an equilibrium mixture of 2- and 3-acylpyrroles pyrrolecarbaldehydes also afford isomeric mixtures 81JOC839). The probable mechanism of these rearrangements is shown in Scheme 65. A similar mechanism has been proposed for the isomerization of acetylindoles. 

Similar transformations are based upon 1,2-thiazine 2,2-dioxides (5-sultones), easily obtained by treating a,/3- or /3,y-unsaturated ketones with acetic anhydride and sulfuric acid. These compounds can be converted subsequently into furans, thiophenes or pyrroles (Scheme 115). 

Oxazoles give acylamino ketones (158) by acid-catalyzed ring scission, although they are somewhat more stable than furans. The oxazole ring is also moderately stable to alkali (74AHCU7)99) as expected, reaction with hydroxide ions is facilitated by electron-with-drawing substituents and fused benzene rings. 

Furan, 3-(4-methylpentanoyl) — see Perilla ketone Furan, 2-methylthio-mass spectrometry, 4, 583 Furan, 3-morpholino-2,5-diphenyl-reaotions... 

The unsaturated tetraoxaquaterene (accompanied by linear condensation products) was first synthesized in 18.5% yield by the acid-catalyzed condensation of furan with acetone in the absence of added lithium salts. Other ketones also condensed with furan to give analogous products in 6-12% yield.A corresponding macrocycle was also prepared in 9% yield from pyrrole and cyclohexanone. The macrocyclic ether products have also been obtained by condensation of short linear condensation products having 2, 3, or 4 furan rings with a carbonyl compound. ... 

Bromochloromethane Methyl ether Methyl ethyl ether Methyl ethyl ketone Methyl formate 2-Methyl furan... 

Furane resins are superior to polyesters and epoxies for resistance to ketones, chlorinated solvents and carbon disulfide. However, as they are... 

Subsequently, Beals and Brown expanded the scope of the earlier work from their laboratory to include the tetraoxaquaterene derived from furan and 3-pentanone. Using 3,3-difurylpentane and diethyl ketone in the presence of dry hydrogen chloride gas, the all-ethyl analog of 6 (mp 249°) was obtained in 20% yield. ... 

Irradiation of cyclic ketones having perfluoroalkyl groups causes cleavage of a ring to yield acyclic products [I74 (equation 44) Similarly, perfluonnated ketones undergo decarbonylation when irradiated [775]. Gas-phase photolysis of perfluorodiazoketones, in the presence of a trapping agent, yields fluorinated furan as a major product [176] (equation 45)... 

In a similar manner, ketones can react with alcohols to form hemiketals. The analogous intramolecular reaction of a ketose sugar such as fructose yields a cyclic hemiketal (Figure 7.6). The five-membered ring thus formed is reminiscent of furan and is referred to as a furanose. The cyclic pyranose and fura-nose forms are the preferred structures for monosaccharides in aqueous solution. At equilibrium, the linear aldehyde or ketone structure is only a minor component of the mixture (generally much less than 1%). 

Zamojski and Jarosz using cyclic ketone 23 with furan that generated a 75 25 ratio of diastereomers 24 and 25. 

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