- Intermolecular [2 + 2] Photocycloaddition of α,β-Unsaturated Sulfones: Catalyst-Free Reaction and Catalytic Variants
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2-Aryl-1-sulfonyl-substituted cyclobutanes were prepared in an intermolecular [2 + 2] photocycloaddition from various α,β-unsaturated sulfones and olefins upon irradiation at λ = 300 nm (26 examples, 60-99% yield). Lewis acids catalyzed the [2 + 2] photocycloaddition of 2-benzimidazolyl styryl sulfones. At short wavelengths, the latter substrates underwent C-S bond cleavage but AlBr3 (5 mol %) allowed for an intermolecular reaction with 2,3-dimethyl-2-butene at longer wavelengths. A chiral-at-metal Lewis acid (2 mol %) facilitated an enantioselective reaction (up to 77% ee).
- Jeremias, Noah,Mohr, Lisa-Marie,Bach, Thorsten
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supporting information
p. 5674 - 5678
(2021/08/03)
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- Synthesis of 3,4-bis(Butylselanyl)selenophenes and 4-alkoxyselenophenes promoted by oxone
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We describe herein an alternative transition-metal-free procedure to access 3,4-bis(butylsela nyl)selenophenes and the so far unprecedented 3-(butylselanyl)-4-alkoxyselenophenes. The protocol involves the 5-endo-dig electrophilic cyclization of 1,3-diynes promoted by electrophilic organosele-nium species, generated in situ through the oxidative cleavage of the Se-Se bond of dibutyl diselenide using Oxone as a green oxidant. The selective formation of the title products was achieved by controlling the solvent identity and the amount of dibutyl diselenide. By using 4.0 equiv of dibutyl diselenide and acetonitrile as solvent at 80?C, four examples of 3,4-bis(butylselanyl)selenophenes were obtained in moderate to good yields (40–78%). When 3.0 equiv of dibutyl diselenide were used, in the presence of aliphatic alcohols as solvent/nucleophiles under reflux, 10 3-(butylselanyl)-4-alkoxyselenophenes were selectively obtained in low to good yields (15–80%).
- Hellwig, Paola S.,Guedes, Jonatan S.,Barcellos, Angelita M.,Perin, Gelson,Lenard?o, Eder J.
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supporting information
(2021/05/28)
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- One-Pot Copper-Catalyzed Three-Component Reaction of Sulfonyl Azides, Alkynes, and Allylamines to Access 2,3-Dihydro-1 H-imi-dazo[1,2-a]indoles
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A copper-catalyzed multicomponent reaction of sulfonyl azides, alkynes, and allylamines affording 2,3-dihydro-1 H-imidazo-[1,2-a]indoles in moderate yields is reported. Four C-N bonds are constructed- by way of azide-alkyne cycloaddition (CuAAC) and double Ullmann-type coupling reactions in a one-pot process.
- Jin, Hongwei,Liu, Daohong,Liu, Yunkui,Zhou, Bingwei
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supporting information
p. 1417 - 1424
(2020/04/27)
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- Copper-catalyzed (4+1) and (3+2) cyclizations of iodonium ylides with alkynes
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The copper(ii)-catalyzed (4+1) cyclizations and copper(i)-catalyzed (3+2) cycloadditions of iodonium ylides and alkynes were successfully developed by employing efficient and safe iodonium ylides instead of traditional diazo compounds. Highly functionaliz
- Liang, Hao,He, Xiaobo,Zhang, Yaqi,Chen, Bin,Ouyang, Jia-Sheng,Li, Yongsu,Pan, Bendu,Subba Reddy, Chitreddy V.,Chan, Wesley Ting Kwok,Qiu, Liqin
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p. 11429 - 11432
(2020/10/12)
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- Visible Light-Catalyzed Decarboxylative Alkynylation of Arenediazonium Salts with Alkynyl Carboxylic Acids: Direct Access to Aryl Alkynes by Organic Photoredox Catalysis
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A convenient method mediated by photoredox catalysis is developed for the direct construction of aryl alkynes. Readily available aromatic diazonium salts have been utilized as the aryl radical source to couple alkynyl carboxylic acids to feature the decarboxylative arylation. A wide range of substrates are amenable to this protocol with broad functional group tolerance, and diversely-functionalized aryl alkynes could be synthesized under mild, neutral and transition metal-free reaction conditions using visible light irradiation. Alongside synthetic sustainability associated with the photocatalytic and transition metal-free operation, another key point of this method is that the organic dye catalyst acts as an excited-state reductant, thus establishing the quenching cycle for radical addition and decarboxylative elimination. (Figure presented.).
- Yang, Liangfeng,Li, Haifeng,Du, Yijun,Cheng, Kai,Qi, Chenze
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p. 5030 - 5041
(2019/11/03)
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- Nickel(ii)-catalyzed tandem C(sp2)-H bond activation and annulation of arenes with gem-dibromoalkenes
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A nickel(ii)/silver(i)-catalyzed tandem C(sp2)-H activation and intramolecular annulation of arenes with dibromoalkenes has been successfully achieved, which offers an efficient approach to the 3-methyleneisoindolin-1-one scaffold. Attractive features of this system include its low cost, ease of operation, and its ability to access a wide range of isoindolinones.
- Shi, Yun,Li, Meng-Sheng,Zhang, Fangdong,Chen, Baohua
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p. 28668 - 28675
(2018/08/29)
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- Palladium-catalyzed tandem C-H functionalization/cyclization strategy for the synthesis of 5-hydroxybenzofuran derivatives
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A palladium-catalyzed benzoquinone C-H functionalization/ cyclization strategy with terminal alkynes was employed for the synthesis of some biologically relevant 2, 3-disubstituted 5-hydroxybenzofuran derivatives. The benzoquinone acts as a reactant as well as an oxidant. During the process, an additional alkyne functionality can be introduced at the C3 position of the benzofuran. Base, ligand, and external oxidant are not required in this protocol.
- Ichake, Sachin S.,Konala, Ashok,Kavala, Veerababurao,Kuo, Chun-Wei,Yao, Ching-Fa
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supporting information
p. 54 - 57
(2017/11/28)
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- 1,1-Dibromoalkenes as versatile reagents to a transition metal-free and stereoselective synthesis of (E)-1-bromo-1-selenoalkenes and ketene selenoacetals
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We describe here a metal-free and selective method for the synthesis of (E)-1-bromo-1-seleno alkenes and ketene selenoacetals by a stoichiometric and temperature-controlled reaction. These protocols employ a diverse array of 1,1-dibromoalkenes and different diaryl diselenides to afford the corresponding products in good yields and in a short reaction time.
- Webber, Rodrigo,Peglow, Thiago J.,Nobre, Patrick C.,Barcellos, Angelita M.,Roehrs, Juliano A.,Schumacher, Ricardo F.,Perin, Gelson
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supporting information
p. 4128 - 4132
(2016/08/24)
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- Combining silver- and organocatalysis: An enantioselective sequential catalytic approach towards pyrano-annulated pyrazoles
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A one-pot asymmetric Michael addition/hydroalkoxylation sequence, catalyzed by a sequential catalytic system consisting of a squaramide and a silver salt, provides a new series of chiral pyrano-annulated pyrazole derivatives in excellent yields (up to 95%) and high enantioselectivities (up to 97% ee).
- Hack, Daniel,Chauhan, Pankaj,Deckers, Kristina,Mizutani, Yusuke,Raabe, Gerhard,Enders, Dieter
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supporting information
p. 2266 - 2269
(2015/02/05)
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- Copper-catalyzed N-alkynylations of sulfoximines with bromoacetylenes
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N-Alkynylated sulfoximines have been obtained by copper-catalyzed cross-coupling reactions starting from NH-sulfoximines and bromoacetylenes in moderate to good yields. The reaction conditions are mild, and the substrate scope is wide.
- Chen, Xiao Yun,Wang, Long,Frings, Marcus,Bolm, Carsten
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supporting information
p. 3796 - 3799
(2014/08/05)
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- Convenient synthesis of 2-aryl-1-haloindolizines from pyridinium salts and 2-aryl-1,1-dihaloalk-1-enes
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2-Aryl-1-haloindolizines were synthesized from pyridinium salts and 2-aryl-1,1-dihaloalk-1-enes using a DBU/THF system. 2-Aryl-1,1-dihaloalk-1-enes containing electron-withdrawing or -donating groups were efficiently converted into the corresponding 2-aryl-1-haloindolizines in moderate to excellent yields. Georg Thieme Verlag Stuttgart.
- Yang, Yiwen,Kuang, Chunxiang,Jin, Hui,Yang, Qing
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supporting information; experimental part
p. 3447 - 3452
(2011/12/04)
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- Synthesis and biological evaluation of polyenylpyrrole derivatives as anticancer agents acting through caspases-dependent apoptosis
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A class of polyenylpyrroles and their analogues were designed from a hit compound identified in a fungus. The compounds synthesized were evaluated for their cell cytotoxicity against human non-small-cell lung carcinoma cell lines A549. Two compounds were found to exhibit high cytotoxicity against A549 cells with IC50 of 0.6 and 0.01 μM, respectively. The underlying mechanisms for the anticancer activity were demonstrated as caspases activation dependent apoptosis induction through loss of mitochondrial membrane potential, release of cytochrome c, increase in B-cell lymphoma-2-associated X protein (Bax) level, and decrease in B-cell lymphoma-2 (Bcl-2) level. The two compounds were nontoxic to normal human lung Beas-2b cells (IC50 > 80 μM), indicating that they are highly selective in their cytotoxicity activities. Furthermore, one compound showed in vivo anticancer activity in human-lung-cancer-cell-bearing mice. These results open promising insights on how these conjugated polyenes mediate cytotoxicity and may provide a molecular rationale for future therapeutic interventions in carcinogenesis.
- Fang, Zhanxiong,Liao, Pei-Chun,Yang, Yu-Liang,Yang, Feng-Ling,Chen, Yi-Lin,Lam, Yulin,Hua, Kuo-Feng,Wu, Shih-Hsiung
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supporting information; experimental part
p. 7967 - 7978
(2011/03/19)
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- A sequential metal-catalyzed C-N bond formation in the synthesis of 2-amido-indoles
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(Chemical Equation Presented) A sequential metal-catalyzed C-N bond formation employing ortho-haloaryl acetylenic bromides is described. The initial amidation is highly selective for C8P-N bond formation, leading to o-haloaryl-substiluted ynami
- Yao, Pei-Yuan,Zhang, Yu,Hsung, Richard P.,Zhao, Kang
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supporting information; experimental part
p. 4275 - 4278
(2009/05/30)
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- An efficient method for one-carbon elongation of aryl aldehydes via their dibromoalkene derivatives
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Various aryl aldehydes were efficiently converted into one-carbon extended aryl acetamides or aryl acetic acids through the reaction of their dibromoalkene derivatives with pyrrolidine in the presence of water under very mild conditions.
- Huh, Dal Ho,Jeong, Ji Sang,Lee, Hee Bong,Ryu, Hoejin,Kim, Young Gyu
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p. 9925 - 9932
(2007/10/03)
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- A novel synthesis of β,β-dibromostyrenes
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A new simple and efficient transformation of aromatic aldehydes to β,β-dibromostyrenes and arylbromoacetylenes is described. The olefination procedure was conducted under mild conditions and in good yields.
- Shastin,Korotchenko,Nenajdenko,Balenkova
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p. 2081 - 2084
(2007/10/03)
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