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1.
Synthesis of Highly Substituted γ‐Butyrolactones by a Gold‐Catalyzed Cascade Reaction of Benzyl Esters
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Maria Camila Blanco Jaimes Alexander Ahrens Daniel Pflästerer Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):427-433
Easily accessible benzylic esters of 3‐butynoic acids in a gold‐catalyzed cyclization/rearrangement cascade reaction provided 3‐propargyl γ‐butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C?C bond is an intermolecular process. Initially propargylic–benzylic esters were used, but alkyl‐substituted benzylic esters worked equally well. In the case of the propargylic–benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl‐substituted γ‐butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one‐pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. 相似文献
2.
Hirofumi Kuroda Emi Hanaki Hironori Izawa Michiko Kano Hiromi Itahashi 《Tetrahedron》2004,60(8):1913-1920
α-Vinylfurans were obtained by phosphine-initiated cyclization of various enynes bearing a carbonyl group at the ene end in the presence of various aldehydes, in moderate to high yields. The reaction may consist of 1,6-addition of phosphine to the enynes, ring closure, and Wittig reaction between the ylid resulting from cyclization and an aldehyde. Thus, various aldehydes were able to be used in the reaction. The reaction was influenced greatly by the substituents at the acetylene position (R1) and the α-position of the carbonyl group (R3). 相似文献
3.
F. I. Zubkov E. V. Nikitina K. F. Turchin A. A. Safronova R. S. Borisov A. V. Varlamov 《Russian Chemical Bulletin》2004,53(4):860-872
The intramolecular Diels—Alder reaction of readily accessible 4-substituted 4-(N-furfuryl)aminobut-1-enes was studied and a new one-step method was developed for the synthesis of 6,8a-epoxy-1,2,3,4,4a,5,6,8a-octahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.01,6]undec-9-ene) derivatives. The [4+2]-cycloaddition proceeds stereoselectively to form exo-adducts. The influence of substituents at the nitrogen atom in 4-(N-furfuryl)aminobut-1-enes on the cycloaddition pathway was examined. 相似文献
4.
trans-2,3-Divinyl epoxides have been found to be good substrates for the generation of carbonyl ylides in CCl4 and 145 °C. These ylides, to a limited extent, undergo isomerization to cis-2,3-divinyl epoxides, leading to the isolation of 4,5-dihydrooxepins. Of greater potential usefulness is the finding that these ylides can be efficiently trapped in an intermolecular sense by a dipolarophile, leading to dihydrofurans. 相似文献
5.
A novel oxidation-ring-contraction reaction took place when 4-substituted Hantzsch 1,4-dihydropyridines were treated with Oxone. This reaction pattern provided a convenient method for the synthesis of polysubstituted furans. 相似文献
6.
Vladimir V. Mel’chin 《Tetrahedron letters》2006,47(25):4117-4120
The cascade rearrangement of novel 4-acetoxy-9-furylnaphtho[2,3-b]furans leading to tetracyclic naphthodifurans derivatives has been developed. The reaction proceeds via double recyclization of both furan rings of the initial molecule, one of the furan rings serving as a 1,3-dicarbonyl compound equivalent. 相似文献
7.
E. Lukevics L. Ignatovich I. Sleiksha V. Romanov S. Grinberga J. Popelis I. Shestakova 《Chemistry of Heterocyclic Compounds》2007,43(2):143-150
A new method was developed for the synthesis of silicon-and germanium-containing acetylfurans and acetylthiophene by metallation
of 2-acetylfuran or 2-acetylthiophene with n-BuLi at low temperature after protection of the carbonyl group with lithium N-methylpiperazide
and reaction of the lithium derivative with various trialkyl-, alkylphenyl-, and cycloalkylchlorosilanes or trialkylchloro(bromo)germanes.
The cytotoxic activity of the new compounds was studied, and it was established that the silicon-and germanium-containing
acetylfurans and acetylthiophenes are substances with low toxicity (LD50 312->2000 mg/kg) and have low cytotoxicity toward HT-1080 and MG-22A tumor cells.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 192–199, February, 2007. 相似文献
8.
9.
Ki-Heon Kim Yong-Chil Seo Hoon Nam Hyun-Tae Joung Jae-Cheon You Dong-Jin Kim Yong-Chan Seo 《Microchemical Journal》2005,80(2):171-181
Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in slag of fly ash from three municipal solid waste (MSW) incinerators were analyzed to observe any changes in characteristics and distribution of their congeners by melting process. Actual concentration and Toxic Equivalent (TEQ) concentration profiles of 17 major congeners of PCDDs/PCDFs for gas, fly ash and melted slag were compared. The distributions of PCDDs/PCDFs in different streams macroscopically showed similarities with the generally known profiles for emission gas from a municipal waste incinerator. The total concentrations of PCDDs/PCDFs in off-gas and fly ash have been known to be a function of incineration conditions and of air pollution control device utilization; however, their normalized distributions were independent of such conditions. The concentrations of PCDDs/PCDFs in the melted slag of fly ash were not related to the concentrations of PCDDs/PCDFs congeners in fly ash but were rather a function of the melting furnace type and operation. The total amount of PCDDs/PCDFs in the melted slag of fly ash contained almost 150–27,000 times less dioxin than that in fly ash, however, the TEQ of dioxin in the slag was reduced by 435–43,500 times, which could enable them to be utilized as recycled construction materials. In normalized TEQ concentration profiles of 17 congeners of PCDDs/PCDFs, the ratio of PCDFs to PCDDs changed from 1.32 to 2.19 by melting, which showed relatively higher portion of furans left in melted slag than those in fly ash. By comparing reduction ratios of different congeners, PCDDs (dioxins) were relatively easier to destruct than PCDFs (furans) during melting process. The most difficult congener to destruct could be octa-chlorinated dibenzofuran (OCDF) among major congeners. For slag cooling methods, dioxin concentration in TEQ of slow cooled slag by air was four times higher than that of fast cooled slag by water. Thus cooling by water is more appropriate with the added beneficial effect of producing granules/particles, which can be utilized as roadbed materials. 相似文献
10.
Satoaki OnitsukaHiroshi Nishino 《Tetrahedron》2003,59(6):755-765
The BF3-catalyzed cyclization of 3-acetyl-1-aryl-2-pentene-1,4-diones 1a-e in the presence of water in boiling tetrahydrofuran gave bis(3-acetyl-5-aryl-2-furyl)methanes 2a-e in 26-79% yields along with a small amount of 3-acetyl-5-aryl-2-methylfurans 3a-e. The exact structure of 2a was determined by X-ray crystallography. The use of a half volume of the solvent for the reaction of 1a resulted in the formation of 2,4-bis(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-phenylfuran (4) together with 2a and 3a. A similar reaction of 1a was carried out in the presence of 3-acetyl-5-(4-methylphenyl)-2-methylfuran (3d) to afford 4-(3-acetyl-5-phenyl-2-furfuryl)-3-acetyl-5-(4-methylphenyl)-2-methylfuran (5) in 49% yield. The BF3-catalyzed reaction of 1a with 2,4-pentanedione in dry tetrahydrofuran at 23°C gave 3-(3-acetyl-5-phenyl-2-furfuryl)-4-hydroxy-3-penten-2-one (6a) and 3-(3-acetyl-2-methyl-4-phenyl-5-furyl)-4-hydroxy-3-penten-2-one (7a) in 66 and 24% yields, respectively. The product distribution depended on the reaction temperature. A similar reaction of 1b-e also yielded the corresponding trisubstituted furans 6b-e and tetrasubstituted furans 7b-e in good yields. These results suggested the presence of the furfuryl carbocation intermediate A during the reaction. The one-pot synthesis of 6a and 7a was also achieved by a similar reaction using phenylglyoxal. The deoxygenation of 1a with triphenylphosphine gave 3a in 88% yield, while 1a was treated with concentrated hydrochloric acid to yield 3-acetyl-2-chloromethyl-5-phenylfuran (8) which was quantitatively transformed in ethanol into 3-acetyl-2-ethoxymethyl-5-phenylfuran (9) and in water into 3-acetyl-5-phenylfurfuryl alcohol (10), respectively. In addition, the Diels-Alder reaction of cyclopantadiene with 1a gave the corresponding [4+2] cycloaddition products 11 and 12. 相似文献