3- Cyclopentene-l,2-diones

T. Hofmann, O. Frank, M. Kemeny, E. Bernardy, M. Habermeyer, U. Weyand, S. Meiers, and D. Marko, Studies on the inhibition of tumor cell growth and microtubule assembly by 3-hydroxy-4-[( )-(2-furyl)methylidene]methyl-3-cyclopentene-l,2-dione, an intensely colored Maillard product formed from carbohydrates and L-proline, in G, 2002, 401-402. 

Fig. 25. Enantioselective verification of the chirogenic Diels/Alder reaction of the Dane diene 1 and 3-ethyl-3-cyclopenten-l,2-dione 2 in the presence of a chiral-nonracemic Ti-complex.

Ring expansion by 2 C-atoms with cyclopropenones 3-Cyclopentene-l,2-diones from ketenes Ph Ph Ph, , Ph Q... 

Cyclopentene-l,2-diol, 42, 51 2-Cyclopentene-1,4-dione, 42, 36 2-Cycloeentene-1-one, 42, 38 2-Cycloeentenone, 42,38 Cyclopropane, bromo-, 43, 9 Cyclopropanecarboxylic add, conversion to bromocyclopropane, 43, 9... 

The four-, five-, and six-membered analogs (178,180, and 182) were also obtained from the diprotonation of squaric acid (3,4-dihydroxy-3-cyclobutene-l,2-dione, 177), tri-O-protonation of croconic acid (4,5-dihydroxy-4-cyclopentene-l,2,3-trione, 179), and tetra-O-protonated rhodizonic acid (5,6-dihydroxy-5-cyclohexene-l,2,3,4-tetraone, 181), respectively. These ions were prepared in either Magic Acid (1 1 FSOsH-SbFs) or fluorosulfuric acid at low temperature and characterized by NMR. Ab initio/IGLO calculations showed that di-O-protonated squaric acid (178) is planar and aromatic, whereas the polyprotonated croconic and rhodizonic acids (180 and 182) have more carboxonium ion character, and no indication was obtained for any significant contributing homoaromatic structures. 

Reactions of diphenylcyclopropenone with ketenes (118 equation 49) in the presence of a catalytic amount of [Ni(CO)4] ord 1 1 cycloadducts, cyclopentene-l,2-diones (119) and -1,3-diones (120), in more than 80% yields. The yields of the products are significantly affected by variation of the solvent used in the reaction, and DMF is the solvent of choice. ... 

D.68) 2-Cyclopenten-l-one, 2-hydroxy-3-methyl-, 2-hydroxy-3-methylcyclopent-2-en-l-one, 3-methylcyclopent-2-en-2-ol-l-one 80-71-7] 1,2-cyclopentanedione, 3-methyl-, 3-methylcyclopentane-l,2-dione, cyclotene, corylone, maple lactone, nussol [765-70-8] FEMA 2700... 

Coupling between cyclopropenone and diphenylketene in the presence of N1(C0)4 afforded cyclopentene-l,2-dione 147 by [3+2] annulatlon (Scheme 2.110) [168]. 

Adducts from 1,2-bis(trimethylsilyloxy)cyclopentene and acetals rearrange in acidic solution to give 3-alkylcyclopentane-l,2-diones (Scheme 42). This behaviour is paralleled in the six-membered-ring series, but contrasts with the sequence starting with the cyclobutene, which ring-expands to give 2-alkylcyclo-pentane-1,3-diones. 

In the presence of nickel carbonyl in DMF, diphenylcyclopropenone reacts with ketenes to produce the cyclopentene-l,2-dione (39) in over 80% yield.This high selectivity is only achieved in DMF, in other solvents significant amounts of diphenylacetylene and cyclopentene-l,3-diones are produced. 

Cyclopentene-l,4-dione is a very reactive dienophile in the Diels-Alder reaction and thus provides access to a variety of compounds containing the reactive /3-dicarbonyl grouping in a five-... 

The BINAL-H reduction works well with alkenic - and alkynic ketones affording alcohols with satisfactory optical purities (Scheme It is noteworthy that (S)-BINAL-H [(S)-(28)] reduces 1-halo-l-octen-3-one and 2-cyclopentene-l,4-dione to give the corresponding carbinols, which are important chiral building blocks for the synthesis of prostaglandins by the conjugate addition approach. ... 

In an analogous manner, from 1,3-dithiolylium tetrafluoroborate (88) and 2-cyclopentene-l,4-dione the product (89) was formed, which was oxidized using ddq to yield the dithiafulvalene derivative (90) (Scheme 21) <77CL77>. 

Papoutsis I, Spyroudis S, Varvoglis A. The chemistry of 2-oxido-3-phenyliodonio-l,4-benzoquinones transformation to 2-cyclopentene-l,4-diones and cycloadditions. Tetrahedron Lett. 1994 35 8449-8452. 

The photo-induced exo selectivity was observed in other classic Diels-Alder reactions. Data relating to some exo adducts obtained by reacting cyclopentadiene or cyclohexadiene with 2-methyl-1,4-benzoquinone, 5-hydroxynaphtho-quinone, 4-cyclopentene-l,3-dione and maleic anhydride are given in Scheme 4.13. The presence and amount of EtsN plays a decisive role in reversing the endo selectivity. The possibility that the prevalence of exo adduct is due to isomerization of endo adduct under photolytic conditions was rejected by control experiments, at least for less reactive dienophiles. 

The similar insertion of 93 into 1,2-diphenylcyclopropenone results in cy-clobutenones or o- and p-alkoxyphenols [49]. In the reaction of 93 with 1-alkynylcyclobutenols, 2-alkenyl-4-cyclopentene-l,3-diones are obtained via alkyl shift-ring expansion [50]. (Scheme 33)... 

As compounds exhibiting enhancing effects on CL reactions, a variety of phenols, e.g., firefly luciferin and 6-hydroxybenzothiazole derivatives [12,13], 4-iodophe-nol [14], 4-(4-hydroxyphenyl)thiazole [15], 2-(4,-hydroxy-3 -methoxy-benzyli-dene)-4-cyclopentene-l,3-dione (KIH-201) [16], and 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI) and 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI)[17] (Fig. 6A), and phenylboronic acid derivatives, e.g., 4-phenylylboronic acid [18], 4-iodophenylboronic acid [19], and4-[4,5-di(2-pyridyl)-l //-imidazol-2-yl]phenylboronic acid (DPPA) [20] (Fig. 6B), in the luminol/hydrogen peroxide/peroxidase system are well known. Rhodamine B and quinine are used as sensitizers in the CL-emitting reaction between cerium (IV) and thiol compounds. This CL reaction was successfully applied to the sensitive determination of various thiol drugs [21-32],... 

Figure 6 Representative (A) phenol-type and (B) phenylboronic acid-type enhancers for luminol/hydrogen peroxide/peroxidase system. KIH-201, 2-(4 -hydroxy-3 -methoxy-benzylidene)-4-cyclopentene-l,3-dione HDI, 2-(4-hydroxyphenyl)-4,5-diphenylimida-zole HPI, 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole DPPA, 4-[4,5-di(2-pyridyl)-1 //iruidazol 2 yl phenylboronic acid).

The observed ring expansion of 2-azido-2-phenylindandione (129) and 2,2-diazido-l,3-indandione (130), along with the established propensity of 2,6-diazido- and 2,5-diazido-l,4-quinones to undergo easy, thermally induced ring contractions to 2-cyano-4-azido-l,3-cyclopentene-diones suggested a unique synthetic route to 2-aza-3-cyano-l,4-quinones (75JA6181). 

The CD induced in 2-(2,4,6-cycloheptatrien-l-ylidine)-4-cyclopentene-l,3-dione upon its inclusion in 6-cyclodextrin was used to obtain full assignment of the observed absorption bands [49]. It was concluded that the low energy band system was composed of three electronic transitions, two of which were polarized perpendicular, and one parallel, with respect to the long molecular axis of the solute. The higher energy band system was found to also consist of three allowed electronic transitions, but two of these were polarized parallel, and one perpendicular, to the long axis of the solute molecule. These deductions were supported by a series of CNDO/S-CI calculations performed on the system. A similar approach was taken to assign the polarizations of the various transitions associated with 2-thioxo-l,3-benzodithiole and 2-selenoxo-1,3-benzodithiole [50]. 

Materials. (Bicyclo[2.2.1]hepta-2,5-diene) rhodium(I) chloride dimer and silver hexafluorophosphate were purchased from Strem Chemical the rhodium complex was recrystallized from acetone prior to use. All silanes (Aldrich) were distilled under a nitrogen atmosphere, freeze-thaw degassed and stored under a nitrogen atmosphere. 4-cyclopentene-l,3-dione (CPDK) from Aldrich was recrystallized from diethyl ether and stored in the dark under a nitrogen atmosphere at -40°C. All solvents were distilled under nitrogen from appropriate drying agents immediately prior to use. 

Similarly Ni catalysts are useful substitutes to Pd for the selective olefin reduction in an a,/8-unsaturated ketone. Finely divided Ni (and partially deactivated by washing it with a 0.1% MeOH solution of acetic acid) in a mixture 5% HCCl3/EtOH is efficient at RT and atm P. Neutral catalysts, U—Ni—N, obtained by refluxing precipitated Ni with isopropanol, also shows selectivity, mesityl oxide being reduced to methyl-1 pentanone-2 . 4-Cyclopentene-l,3-dione, 5, can be converted into 1,3-cyclo-pentanedione, 6, by hydrogenation over partially deactivated neutral Ni catalyst ... 

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