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1. Absolute Configuration of Hydroxysqualene. An Intermediate in Bacterial Hopanoid Biosynthesis

Author:
Pan, Jian-Jung; Ramamoorthy, Gurusankar; Poulter, C. Dale
Source:
Organic letters 2016 v.18 no.3 pp. 512-515
ISSN:
1523-7052
Subject:
bacteria; biosynthesis; chemical structure; hopanoids; solvolysis; spectroscopy; squalene
Abstract:
... Squalene (SQ) is a key intermediate in hopanoid biosynthesis. Many bacteria synthesize SQ from farnesyl diphosphate (FPP) in three steps: FPP to (1R,2R,3R)-presqualene diphosphate (PSPP), (1R,2R,3R)-PSPP to hydroxysqualene (HSQ), and HSQ to SQ. Chemical, biochemical, and spectroscopic methods were used to establish that HSQ synthase synthesizes (S)-HSQ. In contrast, eukaryotic squalene synthase ca ...
DOI:
10.1021/acs.orglett.5b03546

2. Access to Different Isomeric Dibenzoxazepinones through Copper-Catalyzed C–H Etherification and C–N Bond Construction with Controllable Smiles Rearrangement

Author:
Zhou, Yunfei; Zhu, Jianming; Li, Bo; Zhang, Yong; Feng, Jia; Hall, Adrian; Shi, Jiye; Zhu, Weiliang
Source:
Organic letters 2016 v.18 no.3 pp. 380-383
ISSN:
1523-7052
Subject:
aminoquinolines; benzamides; chemical bonding; chemical reactions; copper; moieties
Abstract:
... An efficient new way to access two regio-isomeric dibenzoxazepinones is reported from 8-aminoquinoline benzamides and 2-bromophenols. Through choice of conditions, the reaction proceeds either through a sequential C–H etherification and subsequent Goldberg reaction, both controlled by the aminoquinoline group and Cu(I), or via a C–H etherification and subsequent Smiles rearrangement promoted by Cu ...
DOI:
10.1021/acs.orglett.5b03378

3. Access to the 2H-Tetrahydro-4,6-dioxo-1,2-oxazine Ring System from Nitrone via a Tandem Nucleophilic Addition and Transesterification Reaction

Author:
Yang, Shaoqiang; Liao, Daohong; Tian, Xiaoqi; Lei, Xiaoguang
Source:
Organic letters 2016 v.18 no.3 pp. 376-379
ISSN:
1523-7052
Subject:
Lewis bases; antibacterial properties; chemical structure; organic compounds; transesterification
Abstract:
... A general and efficient synthesis of the 2H-tetrahydro-4,6-dioxo-1,2-oxazine ring system through a tandem nucleophilic addition and transesterification reaction is described. The reaction is highly functional-group-tolerant and proceeds under mild conditions, affording the corresponding products in good to excellent yields. This method represents the first general synthetic route to access this he ...
DOI:
10.1021/acs.orglett.5b03374

4. Access to the Pyrroloindoline Core via [3 + 2] Annulation as well as the Application in the Synthetic Approach to (±)-Minfiensine

Author:
Ji, Wenzhi; Yao, Licheng; Liao, Xuebin
Source:
Organic letters 2016 v.18 no.3 pp. 628-630
ISSN:
1523-7052
Subject:
ambient temperature; cations; chemical structure; cycloaddition reactions; indoles; methodology; solvents
Abstract:
... A [3 + 2] formal cycloaddition reaction using aza-oxyallyl cation as a synthetic synthon was developed to construct the pyrroloindololine core. With this novel method, a variety of C3-substituted indoles were readily converted into the corresponding pyrroloindoline analogues at room temperature in the mixed solvents. To further demonstrate the utility of this method, a synthetic approach to the to ...
DOI:
10.1021/acs.orglett.5b03421

5. Ag2CO3/CA-AA-AmidPhos Multifunctional Catalysis in the Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides

Author:
Wang, Haifei; Deng, Qifu; Zhou, Zhipeng; Hu, Shunqin; Liu, Zhiguo; Zhou, Li-Yi
Source:
Organic letters 2016 v.18 no.3 pp. 404-407
ISSN:
1523-7052
Subject:
catalysts; catalytic activity; chemical structure; cycloaddition reactions; enantioselectivity; pyrrolidines
Abstract:
... The new Ag₂CO₃/CA-AA-amidphos complexes have been demonstrated as highly efficient multifunctional catalysts in the asymmetric 1,3-dipolar cycloaddition of azomethine ylides. Under optimal conditions, highly functionalized endo-4 pyrrolidines were obtained with excellent yields (up to 99% yield) and enantioselectivities (up to 96% ee). ...
DOI:
10.1021/acs.orglett.5b03430

6. [3 + 2]-Annulations of N-Hydroxy Allenylamines with Nitrosoarenes: One-Pot Synthesis of Substituted Indole Products

Author:
Sharma, Pankaj; Liu, Rai-Shung
Source:
Organic letters 2016 v.18 no.3 pp. 412-415
ISSN:
1523-7052
Subject:
bioactive compounds; chemical reactions; chemical structure; oxygen; synthesis; toluene
Abstract:
... In the presence of O₂ and an IPrCuCl additive (5 mol %), [3 + 2]-annulation reactions of N-hydroxyaniline with nitrosobenzenes in cold toluene form isoxazolidin-5-ol derivatives. Heating the same reaction mixture with DBU in toluene affords highly functionalized indole products efficiently. This method provides short synthesis of several bioactive molecules including WIN 48098, WIN 53365, and JWH ...
DOI:
10.1021/acs.orglett.5b03447

7. A Pot-Economical Approach to the Total Synthesis of Sch-725674

Author:
Bodugam, Mahipal; Javed, Salim; Ganguly, Arghya; Torres, Jessica; Hanson, Paul R.
Source:
Organic letters 2016 v.18 no.3 pp. 516-519
ISSN:
1523-7052
Subject:
chemical structure; chemoselectivity; hydrogenation; organic compounds; phosphates
Abstract:
... A pot-economical total synthesis of antifungal Sch-725674, 1, is reported. The approach takes advantage of a number of one-pot, sequential transformations, including a phosphate tether-mediated one-pot, sequential RCM/CM/chemoselective hydrogenation protocol, a one-pot tosylation/acrylation sequence, and a one-pot, sequential Finkelstein reaction/Boord olefination/acetonide deprotection procedure ...
DOI:
10.1021/acs.orglett.5b03547
PubMed:
26760683
PubMed Central:
PMC4852165

8. A Route to α-Fluoroalkyl Sulfides from α-Fluorodiaroylmethanes

Author:
Lin, Ya-mei; Yi, Wen-bin; Shen, Wan-zhao; Lu, Guo-ping
Source:
Organic letters 2016 v.18 no.3 pp. 592-595
ISSN:
1523-7052
Subject:
Lewis bases; aromatic hydrocarbons; cations; chemical reactions; chemical structure; selectivity (chemistry); sulfides; temperature
Abstract:
... α,α-Difluorodiaroylmethane can be used as a nucleophilic difluoromethylation reagent for generating α-thioaryl-α,α-difluoroacetophenones (Ar¹COCF₂SAr) and difluoromethylthiolated arenes (ArSCF₂H) under transition-metal-free conditions. The reaction selectivity is mainly dependent on temperature. The method has also been extended to the synthesis of α-thioaryl-α-monofluoroacetophenones using α-mono ...
DOI:
10.1021/acs.orglett.5b03654

9. 1,1′-Carbonyldiimidazole (CDI) Mediated Coupling and Cyclization To Generate [1,2,4]Triazolo[4,3-a]pyridines

Author:
Baucom, Kyle D.; Jones, Siân C.; Roberts, Scott W.
Source:
Organic letters 2016 v.18 no.3 pp. 560-563
ISSN:
1523-7052
Subject:
chemical structure; cyclization reactions; pyridines
Abstract:
... An operationally efficient CDI mediated tandem coupling and cyclization reaction to generate [1,2,4]triazolo[4,3-a]pyridines has been reported. The reaction conditions and scope were investigated, and the methodology was demonstrated in batch mode as well as in a continuous process. ...
DOI:
10.1021/acs.orglett.5b03589

10. Cipacinoids A–D, Four Limonoids with Spirocyclic Skeletons from Cipadessa cinerascens

Author:
Yu, Jin-Hai; Liu, Qun-Fang; Sheng, Li; Wang, Guo-Cai; Li, Jia; Yue, Jian-Min
Source:
Organic letters 2016 v.18 no.3 pp. 444-447
ISSN:
1523-7052
Subject:
Cipadessa baccifera; X-ray diffraction; chemical reactions; chemical structure; limonoids; protein-tyrosine-phosphatase; spectral analysis
Abstract:
... Four limonoids, cipacinoids A–D (1–4), with spirocyclic skeletons were isolated from Cipadessa cinerascens. It is particularly notable that compounds 1–3 had a 17S-configuration for the first time in the limonoid family. Their structures with absolute configurations were assigned by spectroscopic data, X-ray crystallography, and CD analysis. Compound 1 showed moderate protein tyrosine phosphatase ...
DOI:
10.1021/acs.orglett.5b03487

11. Copper-Catalyzed Denitrogenative Transannulation Reaction of Pyridotriazoles: Synthesis of Imidazo[1,5-a]pyridines with Amines and Amino Acids

Author:
Joshi, Abhisek; Chandra Mohan, Darapaneni; Adimurthy, Subbarayappa
Source:
Organic letters 2016 v.18 no.3 pp. 464-467
ISSN:
1523-7052
Subject:
amines; amino acids; chemical reactions; moieties; pyridines
Abstract:
... The copper-catalyzed aerobic oxidative synthesis of imidazo[1,5-a]pyridines via cascade denitrogenative transannulation reaction of pyridotriazoles with benzylamines with good functional group tolerance is developed. The present methodology is also applicable to amino acids to obtain imidazo[1,5-a]pyridines via decarboxylative oxidative cyclization. ...
DOI:
10.1021/acs.orglett.5b03509

12. Copper-Catalyzed Intermolecular Chloro- and Bromotrifluoromethylation of Alkenes

Author:
Fu, Mingyang; Chen, Long; Jiang, Yongpeng; Jiang, Zhong-Xing; Yang, Zhigang
Source:
Organic letters 2016 v.18 no.3 pp. 348-351
ISSN:
1523-7052
Subject:
alkenes; chemical reactions; chemical structure
Abstract:
... A highly practical copper-catalyzed intermolecular halotrifluoromethylation of alkenes has been developed under mild reaction conditions. A variety of Cl/Br-containing trifluoromethyl derivatives were directly synthesized from a wide range of alkenes, including electron-deficient and unactivated alkenes. ...
DOI:
10.1021/acs.orglett.5b03080

13. Copper-Catalyzed Regioselective 1,2-Alkylesterification of Dienes to Allylic Esters

Author:
Li, Yougui; Han, Yulong; Xiong, Haigen; Zhu, Nengbo; Qian, Bo; Ye, Changqing; Kantchev, Eric Assen B.; Bao, Hongli
Source:
Organic letters 2016 v.18 no.3 pp. 392-395
ISSN:
1523-7052
Subject:
byproducts; carbon; carbon dioxide; chemical reactions; chemical structure; esters; peroxides; regioselectivity
Abstract:
... Copper catalyzed 1,2-alkylesterification of 1,3-dienes with diacyl peroxides affords branched allylic esters in excellent regioselectivity, including products with a newly generated fully substituted carbon center. The only byproduct is CO₂. The reaction proceeds by a radical mechanism as suggested by spin trap and crossover experiments. ...
DOI:
10.1021/acs.orglett.5b03399

14. Core-Fluorinated Naphthalene Diimides: Synthesis, Characterization, and Application in n-Type Organic Field-Effect Transistors

Author:
Yuan, Zhongyi; Ma, Yingjie; Geßner, Thomas; Li, Mengmeng; Chen, Long; Eustachi, Michael; Weitz, R. Thomas; Li, Chen; Müllen, Klaus
Source:
Organic letters 2016 v.18 no.3 pp. 456-459
ISSN:
1523-7052
Subject:
chemical reactions; chemical structure; dioxane; energy; halogens; naphthalene; transistors; vapors
Abstract:
... A series of difluoro- and tetrafluoro-substituted naphthalene diimides (NDIs) were synthesized by halogen exchange reactions of corresponding bromo-NDIs with CsF in dioxane. Two strong electron acceptor molecules 6 and 8 with low-lying LUMO energy levels of −4.27 and −4.54 eV were obtained, starting from tetrafluoro-NDI. Organic field-effect transistors (OFETs) based on these fluorinated NDIs were ...
DOI:
10.1021/acs.orglett.5b03489

15. Cross-Coupling Hydrogen Evolution by Visible Light Photocatalysis Toward C(sp2)–P Formation: Metal-Free C–H Functionalization of Thiazole Derivatives with Diarylphosphine Oxides

Author:
Luo, Kai; Chen, Yao-Zhong; Yang, Wen-Chao; Zhu, Jie; Wu, Lei
Source:
Organic letters 2016 v.18 no.3 pp. 452-455
ISSN:
1523-7052
Subject:
byproducts; carbon-hydrogen bond activation; cross-coupling reactions; hydrogen; hydrogen production; moieties; oxidants; oxides; phosphine; phosphorylation; photocatalysis; redox reactions; thiazoles
Abstract:
... Visible light along with 5 mol % eosin B catalyzed the first direct C–H phosphorylation of thiazole derivatives with diarylphosphine oxides by a photoredox process in the absence of an external oxidant. The scope of thiazoles and phosphine oxides was further investigated, as was functional group tolerance. The general and operational simplicity provides a novel metal and oxidant-free alternative f ...
DOI:
10.1021/acs.orglett.5b03497

16. Cross-Coupling of Meyer–Schuster Intermediates under Dual Gold–Photoredox Catalysis

Author:
Um, Jiwon; Yun, Hokeun; Shin, Seunghoon
Source:
Organic letters 2016 v.18 no.3 pp. 484-487
ISSN:
1523-7052
Subject:
aromatic hydrocarbons; catalytic activity; cross-coupling reactions; diazonium compounds; dissociation; gold; moieties; redox reactions; salts
Abstract:
... Under dual gold/photoredox catalytic conditions, intermediates from the Meyer–Schuster rearrangement underwent an efficient cross-coupling with arene diazonium salts, leading to α-arylated enones. Diazonium salts assisted the dissociation of the propargyl hydroxyl group by forming alkoxydiazenes in the Meyer–Schuster rearrangement, and the coupling was proposed to proceed through an allenyl methyl ...
DOI:
10.1021/acs.orglett.5b03531

17. Csp3–P versus Csp2–P Bond Formation: Catalyst-Controlled Highly Regioselective Tandem Reaction of Ene-Yne-Ketones with H-Phosphonates

Author:
Yu, Yue; Yi, Songjian; Zhu, Chuanle; Hu, Weigao; Gao, Bingjie; Chen, Yang; Wu, Wanqing; Jiang, Huanfeng
Source:
Organic letters 2016 v.18 no.3 pp. 400-403
ISSN:
1523-7052
Subject:
carbenes; catalysts; chemical reactions; chemical structure; copper; furans; nuclear magnetic resonance spectroscopy; oxidants; phosphorus; regioselectivity; stable isotopes
Abstract:
... Under copper-catalyzed or base-promoted conditions, a wide range of ene-yne-ketones react with H-phosphonates to afford various phosphorylated furans in good yields. A copper carbene generation or a Michael addition is proposed as the key step in the selective construction of the Csp³–P or Csp²–P bond, which is supported by carbene capture reactions and interval ³¹P NMR experiments. Furthermore, t ...
DOI:
10.1021/acs.orglett.5b03415

18. [3 + 3]-Cycloaddition of Donor–Acceptor Cyclopropanes with Nitrile Imines Generated in Situ: Access to Tetrahydropyridazines

Author:
Garve, Lennart K. B.; Petzold, Martin; Jones, Peter G.; Werz, Daniel B.
Source:
Organic letters 2016 v.18 no.3 pp. 564-567
ISSN:
1523-7052
Subject:
Lewis acids; X-ray diffraction; chemical reactions; chemical structure; chlorides; imines; organochlorine compounds
Abstract:
... Donor–acceptor cyclopropanes are reacted under the influence of a Lewis acid with hydrazonyl chlorides to afford tetrahydropyridazines. Formally, this transformation can be regarded as a [3 + 3]-cycloaddition of three-membered rings and nitrile imines generated in situ. This efficient method provides fast access to a variety of structurally diverse pyridazine derivatives. The structure of a typica ...
DOI:
10.1021/acs.orglett.5b03598

19. DDQ-Mediated Oxidative Radical Cycloisomerization of 1,5-Diynols: Regioselective Synthesis of Benzo[b]fluorenones under Metal-Free Conditions

Author:
Zhu, Hui; Chen, Zhiyuan
Source:
Organic letters 2016 v.18 no.3 pp. 488-491
ISSN:
1523-7052
Subject:
chemoselectivity; cyclization reactions; moieties; organic compounds; regioselectivity
Abstract:
... A regio- and chemoselective oxidative cycloisomerization reaction of acyclic 1,5-diynols has been developed. The reaction proceeds under metal-free reaction conditions with high efficiency and broad functional group tolerance, which offers a general and straightforward access to benzo[b]fluorenones under metal-free conditions. The preliminary mechanistic studies revealed the possible involvement o ...
DOI:
10.1021/acs.orglett.5b03533

20. Direct Arylation of Pyrroles via Indirect Electroreductive C–H Functionalization Using Perylene Bisimide as an Electron-Transfer Mediator

Author:
Sun, Guoquan; Ren, Shuya; Zhu, Xinhai; Huang, Manna; Wan, Yiqian
Source:
Organic letters 2016 v.18 no.3 pp. 544-547
ISSN:
1523-7052
Subject:
arylation; carbon-hydrogen bond activation; chemical structure; electron transfer; organic halogen compounds; pyrroles
Abstract:
... The indirect electroreductive coupling of aryl halides and pyrroles was successfully conducted using a catalytic amount of perylene bisimide as a mediator in 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([EMIM]NTf₂)/DMSO. ...
DOI:
10.1021/acs.orglett.5b03581