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Journal of Organic Chemistry

Yan Zhu, Juwen Gong, Yonghui Wang
A novel and efficient free radical promoted copper-catalyzed decarboxylative alkylation of α,β-unsaturated carboxylic acids with ICH2CF3 and its analogues has been developed. This methodology provides with a convenient access to the synthesis of allylic trifluoromethyl and β-CF3 ketone containing compounds as well as other biologically useful fluorinated molecules and materials.
June 21, 2017: Journal of Organic Chemistry
Nina A Nedolya, Ol'ga A Tarasova, Alexander I Albanov, Boris A Trofimov
A novel simple approach to highly functionalized multisubstituted thiophenes such as alkyl 4-alkoxy-5-amino-3-methylthiophene-2-carboxylates through the one-pot sequential reaction of α-lithiated alkoxyallenes with isothiocyanates and alkyl 2-bromoacetates has been discovered. The process proceeds quickly (30-45 min) via in situ formation and intramolecular cyclization of alkyl 2-[(2-alkoxybuta-2,3-dienimidoyl)sulfanyl]acetates (1-aza-1,3,4-trienes).
June 21, 2017: Journal of Organic Chemistry
Glenn A Pullella, Duncan Andrew Wild, Gareth L Nealon, Mikhail Elyashberg, Matthew J Piggott
1,5,7-Trihydroxy-6H-indeno[1,2-b]anthracene-6,11,13-trione (1), proposed to be the antitubercular natural product eucapsitrione, has been synthesised in 43% overall yield, and six steps, including a key Suzuki-Miyaura biaryl coupling and a directed remote metalation (DReM)-initiated cyclisation. The physical and spectroscopic properties of 1 do not match the data reported for the natural product. At this time there is insufficient information available to enable a structure reassignment. During the optimization of the Suzuki-Miyaura coupling an unprecedented biaryl coupling ortho to the borono group was observed...
June 21, 2017: Journal of Organic Chemistry
Juan Francisco González, Damiano Rocchi, Tomas Tejero, Pedro Merino, J Carlos Menéndez
The microwave-promoted three-component reaction between o-nitrochalcones, primary amines and β-dicarbonyl compounds in the presence of Ce(IV) ammonium nitrate constitutes the first example of a multicomponent carbazole syntrhesis. This reaction furnishes highly substituted and functionalized carbazole derivatives via a double annulation process that generates two C-C and two C-N bonds, with water as the only side product. Mechanistically, this process has some unusual features that include an intramolecular coupled hydrogenation-dehydrogenation process, the functionalization of a C-H group by direct attack onto a nitrogen function and a CAN-catalyzed reduction via hydride transfer from ethanol...
June 21, 2017: Journal of Organic Chemistry
Ritabrata Datta, Subrata Ghosh
First asymmetric synthesis of the marine natural product (-)-gracilioether F is described from a D-mannitol derived known compound. The key step involves intramolecular 1, 4-conjugate addition of a hydroxymethyl radical generated from Ti (III) mediated ring opening of a terminal epoxy ring tethered to a butenolide to produce stereoselectively a five-membered ring fused bicyclic lactone, the core structure present in gracilioether F.
June 21, 2017: Journal of Organic Chemistry
Hanuman Popat Kalmode, Kishor L Handore, D Srinivasa Reddy
Serendipitous findings of an acid mediated skeletal rearrangement of bicyclo-β-ketoester having cyclopropyl ring to access fused tricyclic γ-butyrolactones has been described. This novel transformation has been optimized to 30 mole % p-toluenesulphonic acid (p-TSA) in toluene using Dean-Stark apparatus, where the aldol condensation, cyclopropyl ring opening followed by cyclization took place in a single-pot operation. The resulting tricyclic compounds are interesting chemotype with natural product resemblance, may find useful applications in the future...
June 21, 2017: Journal of Organic Chemistry
Desaboini Nageswar Rao, Sk Rasheed, Gaurav Raina, Qazi Naveed Ahmed, Chaitanya Kumar Jaladanki, Prasad V Bharatam, Parthasarathi Das
A cobalt-catalyzed proton-coupled electron transfer (PCET) mediated regioselective ortho-specific nitration of aromatic C(sp2)-H bonds using chelation assisted removable vicinal diamine directing groups has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2•4H2O as the catalyst and AgNO2 utilized as nitro source as well as terminal oxidant in the presence of O2 as a external oxidant, no external base and additives were required for this process. By doing controlled experiments and mechanistic investigations with DFT calculations revealed that the reaction proceeds through PCET promoted nitro functional group transfer pathway...
June 21, 2017: Journal of Organic Chemistry
Katharina J Hock, Renè Hommelsheim, Lucas Mertens, Junming Ho, Thanh Vinh Nguyen, Rene M Koenigs
Trifluoromethyl-substituted cyclopropanes are an attractive family of building blocks for the construction of pharmaceutical and agrochemical agents. This work demonstrated the utilization of fluorinated sulfur ylides as versatile reagents for Corey-Chaykovsky cyclopropanation reactions of nitro styrenes. This protocol favored the synthesis of cis-configured trifluoromethyl cyclopropanes on a broad range of substrates with excellent yields and good diastereoselectivity.
June 21, 2017: Journal of Organic Chemistry
Chieh-Kai Chan, Nai-Chen Hsueh, Yu-Lin Tsai, Meng-Yang Chang
In this article, a facile two-step and one-pot synthetic route for the preparation of substituted aryl dihydronaphthalenes starting from 2-allylbenzaldehydes via Grignard 1,2-addition and Bi(OTf)3-catalyzed intramolecular olefinic cyclization has been developed. A five-membered ring indene skeleton is also prepared via olefin isomerization, 1,2-addition followed by cyclization. Some key structures are determined using single-crystal X-ray crystallography. A possible mechanism is presented herein.
June 21, 2017: Journal of Organic Chemistry
Justin B Diccianni, Tyler Heitmann, Tianning Diao
Carboxylate groups are ubiquitous in bioactive molecules. The syntheses of carboxylates from petroleum feedstock require a series of oxidation reactions. CO2 represents a cheap and sustainable, preoxidized C1 source. Herein, we describe a simple, selective, and mild procedure for the construction of (hetero)cyclic α,β-unsaturated carboxylic acids from 1,6- and 1,7-enyes and CO2. Terminal 1,7-enynes and sterically hindered alkenes experience a change in regioselectivity and form unconjugated carboxylic acids...
June 21, 2017: Journal of Organic Chemistry
Wei-Si Guo, Qian Dou, Jian Hou, Li-Rong Wen, Ming Li
A novel Mn(II)-promoted tandem phosphorylation/cyclization reaction of 2-biaryl isothiocyanates with phosphine oxides is described. This is the first general method to synthesize 6-phosporylated phenanthridines from 2-biaryl isothiocyanates. The approach is featured by oxidant-free, low loading of P-reagent, easy operation, and high functional group tolerance.
June 21, 2017: Journal of Organic Chemistry
Raghunath Reddy Anugu, Rambabu Chegondi
Catalytic tandem diastereoselective desymmetrization of cyclohexadienone-containing 1,6-enynes has been achieved through copper-catalyzed [3 + 2]-cycloaddition followed by ketenimine formation and subsequent intramolecular conjugate addition. The cascade reaction provides cis-hydrobenzofurans in good yields with excellent diastereoselectivity. The exo- or endo-selectivity of bicyclic scaffolds depends on the selection of the base in the reaction. In addition, N-tethered bicyclic products further transformed into tricyclic compounds via intramolecular Michael addition...
June 21, 2017: Journal of Organic Chemistry
Shoko Yamazaki, Taku Naito, Mamiko Niina, Kiyomi Kakiuchi
Catalytic cyclization of amides of ethenetricarboxylate bearing ether and acetal groups has been examined. The reaction of the amides bearing cyclic ether and acetal groups in the presence of Lewis acid such as Sc(OTf)3 gave spirocyclic piperidine derivatives as major products. The cyclized products may be formed via intramolecular hydride transfer. The reaction mechanism was examined by the DFT calculations. The scope and limitations of the hydride transfer/cyclization reactions of amides of ethenetricarboxylates was investigated, and morpholine formation by intramolecular oxy-Michael addition was also found...
June 21, 2017: Journal of Organic Chemistry
Riyadh Ahmed Atto Al-Shuaeeb, David Montoir, Mouad Alami, Samir Messaoudi
Buchwald-Hartwig-Migita cross-coupling of 1-thiosugars with 2-iodoglycals has been accomplished under mild and operationally simple reaction conditions through the use of Pd-G3 XantPhos palladacycle precatalyst. This new methodology has been successfully applied to a variety of α- or β-mono-, di-, and polythiosugar derivatives to synthesize efficiently a series of (1 → 2)-S-linked thiosaccharides and S-linked glycoconjugates, which are difficult to synthesize by classical methods.
June 21, 2017: Journal of Organic Chemistry
Pavel K Mykhailiuk, Vladimir Kubyshkin, Thorsten Bach, Nediljko Budisa
The triple-helical structure of collagen, the most abundant protein in animal bodies, owes its stability to post-translationally installed hydroxyl groups at position 4 of prolyl residues. To shed light on the nature of this phenomenon, we have examined the influence of the 4-substituent on the amide isomerism in peptidyl-prolyl analogues. The rigid bicyclic skeleton of 2,4-methanoprolines allowed us to follow the through-bond impact of the substituent group (electronic effect) without the side-chain conformation being affected by a stereoelectronic effect...
June 21, 2017: Journal of Organic Chemistry
Lan Zheng, Yong-Min Liang
Copper-catalyzed [2 + 2 + 3] annulation of 1,6-enynes with α-bromo-1,3-dicarbonyl compounds is described. This reaction provides facile access to seven-membered dihydrooxepines for epidithiodiketopiperazines with two newly formed C-C bonds and one C-O bond.
June 21, 2017: Journal of Organic Chemistry
Chiara Pedroli, Davide Ravelli, Stefano Protti, Angelo Albini, Maurizio Fagnoni
The reactivity of α,n-didehydrotoluenes (DHTs) in protic media (organic/aqueous mixtures) was explored by means of a combined computational and experimental approach. These intermediates were generated via a photoinduced double elimination process occurring in (chlorobenzyl)trimethylsilanes and led to the formation of a varied products distribution, depending on the isomer tested. Irradiation of ortho- and para-derivatives resulted, respectively, in the formation of triplet α,2- and α,4-DHTs, whose diradical reactivity led to both radical and polar products...
June 21, 2017: Journal of Organic Chemistry
Naruki Konishi, Tatsuya Shirahata, Masaki Yokoyama, Tatsuya Katsumi, Yoshikazu Ito, Nozomu Hirata, Takashi Nishino, Kazuishi Makino, Noriko Sato, Takayuki Nagai, Hiroaki Kiyohara, Haruki Yamada, Eisuke Kaji, Yoshinori Kobayashi
We report the first synthesis of a series of bisdesmosidic oleanolic acid saponins using microflow reactor Comet X-01 via a continuous flow glycosylation-batch deprotection sequence. The main results of this study can be summarized as follows: (1) The microfluidic glycosylation of oleanolic acid at C-28 was achieved in quantitative yield and was applied to the synthesis of six C-28-monoglycosidic saponins. (2) The microfluidic glycosylation of oleanolic acid at C-3 was achieved in good yield without orthoester byproduct formation and was applied to the synthesis of three bisdesmosidic saponins...
June 21, 2017: Journal of Organic Chemistry
Yu Liu, Qiao-Lin Wang, Cong-Shan Zhou, Bi-Quan Xiong, Pan-Liang Zhang, Chang-An Yang, Ke-Wen Tang
A novel metal-free oxidative ring-openning/cyclizaiton of methylenecyclopropanes with ethers has been established for the synthesis of diverse 2-substituted 3,4-dihydronaphthalenes with high selectivity and efficiency. This oxidative cyclization is achieved by C(sp3)-H functionalization, ring-openning and cyclization, and this method represents a new example of methylenecyclopropane oxidative cyclization with an aromatic carbon and a C(sp3)-H bond by simultaneously forming two new carbon-carbon bonds.
June 20, 2017: Journal of Organic Chemistry
Laurent Legentil, Yari Cabezas, Olivier Tasseau, Charles Tellier, Franck Daligault, Vincent Ferrieres
Koenigs-Knorr glycosylation of acceptors with more than one free hydroxyl group by 2,3,5,6-tetrabenzoyl galactofuranosyl bromide was performed using diphenylborinic acid 2-aminoethyl ester (DPBA) as inducer of regioselectivity. High regioselectivity for the glycosylation on the equatorial hydroxyl group of the acceptor was obtained thanks to the transient formation of a borinate adduct of the corresponding 1,2-cis diol. Nevertheless formation of orthoester by-products hampered the efficiency of the method. Interestingly electron-withdrawing groups on O-6 or on C-1 of the acceptor displaced the reaction in favour of the desired galactofuranosyl containing disaccharide...
June 20, 2017: Journal of Organic Chemistry
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