A Brønsted acid catalysed enantioselective Biginelli reaction

A Bronsted acid catalysed enantioselective Biginelli reaction

Green Chem., 2017, Advance Article
DOI: 10.1039/C6GC03274E, Paper

Margherita Barbero, Silvano Cadamuro, Stefano Dughera
A chiral derivative of 1,2-benzenedisulfonimide, namely (-)-4,5-dimethyl-3,6-bis(o-tolyl)-1,2-benzenedisulfonimide is herein proven to be an efficient chiral catalyst in a one pot three-component Biginelli reaction.

Margherita Barbero,^a   Silvano Cadamuro^a and  Stefano Dughera*^a  

*Corresponding authors

^aDipartimento di Chimica, Università di Torino, C.so Massimo d’Azeglio 48, 10125 Torino, Italy
E-mail: stefano.dughera@unito.it

Green Chem., 2017, Advance Article

DOI: 10.1039/C6GC03274E

A chiral derivative of 1,2-benzenedisulfonimide, namely (−)-4,5-dimethyl-3,6-bis(o-tolyl)-1,2-benzenedisulfonimide is herein proven to be an efficient chiral catalyst in a one pot three-component Biginelli reaction. In fact the yields of the target dihydropyrimidines were very high (25 examples; average 91%) and enantiomeric excesses were always excellent (14 examples; average 97%). Ultimately, we herein propose a procedure that displays a number of benefits and advantages including the total absence of solvents, mild reaction conditions, relatively short reaction times and stoichiometric reagent ratios. Target dihydropyrimidines are obtained in adequate purity, making further chromatographic purification unnecessary. Moreover, the chiral catalyst was easily recovered from the reaction mixture and reused, without the loss of catalytic activity.

(R)-(-)-Ethyl 6-methyl-4-phenyl-2-thioxo-3,4-dihydropyrimidine-5-carboxylate (5a): pale grey solid (135 mg, 98% yield); mp 201–202 °C ( from EtOH; lit17 200–202 °C). 96.4% Ee (GC connected to a J&W Scientific Cyclosil-B column; stationary phase: 30% heptakis (2,3-di-Omethyl-6-O-t-butyldimethylsilyl)-β-cyclodextrin in DB-1701), tR= 12.11 min (major), tR= 12.54 min (minor); [a]D -65.4 (c 0.1 in MeOH).

1H NMR (200 MHz, DMSO-d6): δ = 10.24 (br s, 1H), 9.55 (br s, 1H), 7.31–7.12 (m, 5H), 5.09 (d, J = 3.9 Hz, 1H), 3.92 (q, J = 7.0 Hz, 2H), 2.21 (s, 3H), 1.01 (t, J = 7.0 Hz, 3H);

13C NMR (50 MHz, DMSO-d6): δ = 174.9, 165.8, 145.7, 129.3, 128.3, 127.0, 101.3, 60.2, 54.7, 17.8, 14.7.

MS (m/z, EI): 276 [M+ ] (45), 247 (40), 199 (100). IR (neat) ν (cm−1): 3311 (NH), 3112 (NH), 1665 (CO), 1195 (CS).

USES

////////////Bronsted acid,  catalysed, enantioselective, Biginelli reaction

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Highly chemoselective reduction of nitroarenes over non-noble metal nickel-molybdenum oxide catalysts

Highly chemoselective reduction of nitroarenes over non-noble metal nickel-molybdenum oxide catalysts

Green Chem., 2017, 19,809-815
DOI: 10.1039/C6GC03141B, Paper

Haigen Huang, Xueguang Wang, Xu Li, Chenju Chen, Xiujing Zou, Weizhong Ding, Xionggang Lu
A non-noble Ni-MoO₃/CN@SBA-15 catalyst exhibits unprecedented catalytic activity and chemoselectivity for the reduction of nitroarenes to anilines in ethanol with hydrazine hydrate.

Haigen Huang,^a   Xueguang Wang,*^ab   Xu Li,^a  Chenju Chen,^b   Xiujing Zou,^b   Weizhong Ding^ab and  Xionggang Lu*^ab  

*Corresponding authors

^aState Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200072, China
E-mail: wxg228@shu.edu.cn, luxg@shu.edu.cn

^bShanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, China

Green Chem., 2017,19, 809-815

DOI: 10.1039/C6GC03141B

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC03141B?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

The chemoselective reduction of nitroarenes is an important transformation for the production of arylamines, which are the primary intermediates in the synthesis of pharmaceuticals, agrochemicals and dyes.

Heterogeneous non-noble metal nickel-molybdenum oxide catalysts supported on ordered mesoporous silica SBA-15 (Ni-MoO₃/CN@SBA-15) were prepared for the first time by treating SBA-15-supported nickel-molybdenum oxide materials with 1,10-phenanthroline, and exhibited unprecedented catalytic activity and chemoselectivity for the reduction of various substituted nitroarenes to the corresponding aromatic amines in ethanol with hydrazine hydrate as a hydrogen donor under mild conditions owing to the synergistic effect of metal Ni and MoO₃ species, affording excellent yields of >99% within very short reaction periods (≤60 min).

The Ni-MoO₃/CN@SBA-15 catalysts were highly stable and could easily be recovered by simple filtration or by an external magnetic field for at least ten recycling reactions without any observable loss of catalytic performance or leaching of metal components.

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Synthesis of tetrazines from gem-difluoroalkenes under aerobic conditions at room temperature

Synthesis of tetrazines from gem-difluoroalkenes under aerobic conditions at room temperature

Green Chem., 2017, Advance Article
DOI: 10.1039/C6GC03494B, Paper

Zheng Fang, Wen-Li Hu, De-Yong Liu, Chu-Yi Yu, Xiang-Guo Hu
A procedure for the synthesis of tetrazines from gem-difluoroalkenes under aerobic conditions has been developed.

Zheng Fang,^a   Wen-Li Hu,^a   De-Yong Liu,^a  Chu-Yi Yu^ab and   Xiang-Guo Hu*^a  

*Corresponding authors

^aNational Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, P. R. China
E-mail: huxiangg@iccas.ac.cn

^bBeijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

Green Chem., 2017, Advance Article

DOI: 10.1039/C6GC03494B, http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC03494B?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

An efficient and green procedure for the synthesis of tetrazines has been developed based on an old chemistry reported by Carboni in 1958. Both symmetric and asymmetric 3,6-disubstituted 1,2,4,5-tetrazines can be obtained in moderate to high yields from the corresponding gem-difluoroalkenes under aerobic conditions at room temperature. This work represents a rare example that ambient air is utilized as an oxidant for the synthesis of tetrazines.

Synthesis of symmetric 3,6-dialkyl-1,2,4,5−tetrazine(3a−3h)

To a solution of 1,1−difluoroalkenes (1a, 50 mg, 0.27 mmol) in N,N-dimethylformide (DMF,5 mL) was added hydrazine (80%, 35 mg, 1.35 mmol). After stirring at room temperature for 4−6 hours, saturated ammonium chloride (20 mL) was added and the reaction mixture was extracted with dichloromethane (10 mL×3). The organic layer was combined, dried with anhydrous sodium sulfate. The solvent was concentrated and the crude product was dissolved in a suspension of Ethyl Acetate(5 mL) and 10% potassium carbonate solution(wt%, 5 mL) and stirred at room temperature for 24h under air atomerspere until the organic layer turned into amaranth obviously. The organic layer was collected, dried with anhydrous sodium sulfate. The crude product was purified by flash column chromatography[silica gel(#100–200), toluene] to afford the pure 1,2,4,5−tetrazines(3a−3h).

3,6−bis([1,1’−biphenyl]−4−ylmethyl)−1,2,4,5−tetra zine (3a).

(41 mg, 83%).

purple solid; m.p. 200−202°C;

IR(KBr) nmax/cm−1 2924, 2850, 1488, 1451, 1432, 1388, 851, 750;

1 H NMR (400 MHz, CDCl3) 7.55−7.33 (m, 18H), 4.65 (s, 4H).

13C NMR (100 MHz, CDCl3) δ 169.2, 140.6, 140.4, 134.8, 129.7, 128.8, 127.6, 127.4, 127.1, 40.9;

HRMS (ESI): calcd. for C28H22N4 [M+H]+ 415.19172, found 415.19124.

///////tetrazines,  gem-difluoroalkenes, aerobic conditions, room temperature

Photobiocatalytic alcohol oxidation using LED light sources

Green Chemistry International

Photobiocatalytic alcohol oxidation using LED light sources

Oxidative lactonization of meso-3-methyl-1,5-pentanediol to (S)-4-methyltetrahydro-2H-pyran-2-one using horse liver alcohol dehydrogenase (HLADH) and photocatalytic, aerobic regeneration of NAD⁺.

Green Chem., 2017, 19,376-379
DOI: 10.1039/C6GC02008A, Communication

Open Access

  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.

M. Rauch, S. Schmidt, I. W. C. E. Arends, K. Oppelt, S. Kara, F. Hollmann
The photocatalytic oxidation of NADH using a flavin photocatalyst and a simple blue LED light source is reported.

M. Rauch,^a  S. Schmidt,^a  I. W. C. E. Arends,^a  K. Oppelt,^b  S. Kara^c and  F. Hollmann*^a  

*Corresponding authors

^aDepartment of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629HZ Delft, The Netherlands
E-mail: f.hollmann@tudelft.nl

^b

View original post 484 more words

Asymmetric synthesis of (S)-phenylacetylcarbinol – closing a gap in C–C bond formation

Green Chemistry International

Fig. 3 Stereoselectivities of the new ApPDC-variants for the synthesis of (S)-PAC. The different variants were tested as wet cells, crude cell extracts, and purified enzymes. Reaction conditions: wet cells – 20 mM benzaldehyde; 200 mM pyruvate; 50 mM KPi-buffer (pH 6.5), 2.5 mM MgSO4; 0.1 mM ThDP; 20 °C; 800 rpm, 800 μL reaction volume in 1.5 mL closed glass vials, whole cell catalyst concentration of 50 mg mL−1. Crude cell extract – 20 mM benzaldehyde; 200 mM pyruvate; 50 mM KPi-buffer (pH 6.5), 2.5 mM MgSO4; 0.1 mM ThDP; 20 °C; 800 rpm, 500 μL reaction volume in a 96-well sheet; see ESI chapter 2.1.4–2.1.5† for the catalyst concentration. Purified enzyme – 40 mM benzaldehyde; 200 mM pyruvate; 50 mM KPi-buffer with three different pH values, 2.5 mM MgSO4; 0.1 mM ThDP; 22 °C; 800 rpm…

View original post 386 more words

Pd/Cu-free Heck and Sonogashira cross-coupling reaction by Co nanoparticles immobilized on magnetic chitosan as reusable catalyst

 

Pd/Cu-free Heck and Sonogashira cross-coupling reaction by Co nanoparticles immobilized on magnetic chitosan as reusable catalyst

Green Chem., 2017, Advance Article
DOI: 10.1039/C6GC03377F, Paper

Abdol R. Hajipour, Fatemeh Rezaei, Zahra Khorsandi
Chitosan (CS) is a porous, self-standing, nanofibrillar microsphere that can be used as a metal carrier. Amino groups on CS enable to modulate cobalt coordination using a safe organic ligand (methyl salicylate).

Abdol R. Hajipour,^ab   Fatemeh Rezaei^a and  Zahra Khorsandi^a  

^aDepartment of Chemistry, Isfahan University of Technology, Isfahan 84156, Iran
E-mail: haji@cc.iut.ac.ir
Fax: +98 311 391 2350
Tel: +98 311 391 3262

^bDepartment of Neuroscience, University of Wisconsin, Medical School, Madison, USA

Green Chem., 2017, Advance Article

DOI: 10.1039/C6GC03377F

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC03377F?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Prof. Abdolreza Hajipour

Department of Chemistry

Office : College of Chemistry, Isfahan University of Technology, Isfahan 84156, IR IranEmail : haji [AT] cc.iut.ac.ir or arhajipour [AT] wisc.eduPhone : +98 311 391xxxxFax : +98 311 391xxxxWeb Site : Prof. Abdolreza Hajipour

EDUCATION:

1970-1974               High School, Shahpour high school, Kazerun, IR, Iran

1975-1979               B.S., Chemistry, Department of Chemistry, Isfahan University, Isfahan, I.R. Iran

1981-1983               M.S., Organic Chemistry, Synthesis, Shiraz University, Shiraz, I.R. Iran

Thesis Title: “Synthesis of 2,6,7,11-Tetraphenyl Isobenzofuran B Cyclobutadiene”

Advisor: Professor Habib Firouzabadi

1990-1994               Ph.D., Organic Chemistry, Wollongong University, Australia

Dissertation Title: “Asymmetric Synthesis of Chiral Amines and Benzazepine Alkaloids from Chiral Sulfoxides”

Advisor: Professor Stephen G. Pyne

POSITIONS:

09/94-11/98            Assistant Professor, Isfahan University of Technology

12/98-02/03            Associate Professor, Isfahan University of Technology

03/03-present        Professor, Isfahan University of Technology

02/01-03/02            Visiting Scientist, University of Wisconsin Medical School, Madison, WI

04/02-09/02            Associate Researcher, University of Wisconsin Medical School, Madison, WI

10/02-1/05              Associate Scientist, University of Wisconsin Medical School, Madison, WI

1/04 to present      Senior Scientist, University of Wisconsin Medical School, Madison, WI

 

Chitosan (CS) is a porous, self-standing, nanofibrillar microsphere that can be used as a metal carrier. Amino groups on CS enable to modulate cobalt coordination using a safe organic ligand (methyl salicylate). This catalyst efficiently promotes Heck cross-coupling of a large library of functional substrates under mild and sustainable conditions (polyethylene glycol as solvent at 80 °C in a short time (1 h)). The cobalt complex was also used as a heterogeneous, efficient, inexpensive, and green catalyst for Sonogashira cross-coupling reactions. The reactions of various aryl halides and phenylacetylene provided the corresponding products in moderate to good yields. More importantly, this phosphine, copper, and palladium-free catalyst was stable under the reaction conditions and could be easily reused using an external magnet for at least five successive runs without a discernible decrease in its catalytic activity.

Reaction yields were analyzed by gas chromatography (GC, BEIFEN-3420, detector type: FID, TCD equipped with Nukol™ capillary GC column, size × I.D. 30 m × 0.25 mm, df 0.25 μm). 2,3-Dimethylnaphthalene as was used as internal standard. The gas flow rate of 2 mL min-1; and oven temperature at 80 oC for 15 min and then increased to 170 oC.

General procedure for catalyst preparation The magnetic nanoparticles (MNPs) were prepared according to the method reported in literature64 based on the precipitation of magnetite nanoparticles from a mixture of iron(III) chloride and iron(II) sulfate by ammonia (25% solution in water). Subsequently, in a round-bottom flask equipped with a mechanical stirrer and condenser, a mixture of magnetic nanoparticles and sodium sulfate (20%, w/v) was added to a solution of chitosan (1%, w/v) in acetic acid (2%, w/v) under stirring. Stirring was continued for 1 h to obtain the aqueous suspension of MNPs/CS. Then, the magnetic nanoparticles were separated from the reaction mixture by an external permanent magnet, washed with ethanol and methanol several times, and dried under vacuum at 70 °C. For the preparation of supported methyl salicylate ligands, a solution of ethanol suspension of MNPs/CS (1.5 g per 10 mL) was added to methyl salicylate (6.5 mmol), and the mixture was stirred at 60 °C for 24 h. The final Co-MS@MNPs/CS was obtained as a brown solid by the addition of CoCl2·6H2O (4.2 mmol) dissolved in 10 mL of ethanol to disperse the mixture of MNPs/CS-MS (1.01 g) in ethanol (5 mL) and stirred at 60 °C for 18 h. The resulting complex was collected by an external permanent magnet, washed with ethanol (3 × 10 mL) to remove the unreacted materials, and finally dried in air (89% yield based on the amount of Co in the catalyst determined by ICP).

General procedure for the Heck reaction In a round-bottom flask equipped with a mechanical stirrer, a mixture of K3PO4 (4 eq.), olefin (1.1 mmol), and aryl halide (1 mmol) in PEG (3 mL) was added to 5 mg of catalyst (1.1 mol% of Co) and the flask was equipped with a condenser for refluxing. The abovementioned mixture was heated at 80 °C in an oil bath. The progress of the reaction was monitored by TLC (hexane/EtOAc, 80 : 20) and gas chromatography (GC). After the completion of the reaction, the mixture was diluted with dichloromethane and water. The organic layer was washed with brine, dried over anhydrous MgSO4, and concentrated under reduced pressure. The residue was purified by column chromatography. The products were characterized by comparing their physical properties, such as m.p., IR, 1 H, and 13C NMR spectra, with those reported in literature

General procedure for Sonogashira reaction In a round-bottom flask equipped with a mechanical stirrer, phenyl acetylene (1.2 mmol), aryl halide (1.0 mmol), catalyst (10 mg), and KOH (2 eq.) in DMSO (3 mL) were stirred under an air atmosphere at 140 °C. The progress of the reaction was monitored using TLC and GC. After the completion of the reaction, the mixture was diluted with dichloromethane and water. The organic layer was washed with brine, dried over anhydrous MgSO4, and concentrated under reduced pressure. The product was isolated by column chromatography to afford the corresponding products in 55–80% yields. The products were characterized by comparing their physical properties, such as m.p, IR, 1 H, and 13C NMR spectra with those reported in literature.

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Endogenous water-triggered and ultrasound accelerated synthesis of 1,5-disubstituted tetrazoles via a solvent and catalyst-free Ugi-azide reaction

 

Endogenous water-triggered and ultrasound accelerated synthesis of 1,5-disubstituted tetrazoles via a solvent and catalyst-free Ugi-azide reaction

Green Chem., 2017, Advance Article
DOI: 10.1039/C6GC03324E, Communication

Shrikant G. Pharande, Alma Rosa Corrales Escobosa, Rocio Gamez-Montano
An ultrasound accelerated, environmentally benign Ugi-azide based method was developed for the synthesis of 1,5-disubstituted tetrazoles under solvent and catalyst-free conditions.

Shrikant G. Pharande,^a  Alma Rosa Corrales Escobosa^a and  Rocío Gámez-Montaño*^a  

 *Corresponding authors

^aDepartamento de Química, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta S/N, Col. Noria Alta, Guanajuato, México
E-mail: rociogm@ugto.mx

Green Chem., 2017, Advance Article

DOI: 10.1039/C6GC03324E,  http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC03324E?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

A novel, sustainable, endogenous water-triggered, environmentally friendly, high substrate scope, efficient, solvent-free and catalyst-free Ugi-azide based method for the synthesis of 1,5-disubstituted tetrazoles is described.

Shrikant Pharande

Doctoral student

Universidad de Guanajuato, Guanajuato · Department of Chemistry

Research experience

• Apr 2014–Jun 2014, Research chemist
  TCG Lifesciences · pune
• Mar 2012–Dec 2013, project assistant
  CSIR – National Chemical Laboratory, Pune · Organic Chemistry Division (NCL)

N-((1-(tert-butyl)-1H-tetrazol-5-yl)(4-chlorophenyl)methyl)aniline (4a)

Based on GP, 100 mg 4-Chlorobenzaldehyde (0.71 mmol), 0.065 cm3 aniline (0.71 mmol), 0.080 cm3 ter. Butyl isocyanide (0.71 mmol), and 0.093 cm3 TMS-azide (0.71 mmol) were reacted together to afford 237 mg (97%) as a white solid.

Melting range 144-145oC,

Rf = 0.45 (Hexane-AcOEt = 7/3 V/V),

1H NMR (500 MHz, CDCl3) δ 7.34 – 7.29 (m, 4H), 7.18 – 7.13 (m, 2H), 6.79 – 6.75 (m, 1H), 6.65 (d, J = 7.6 Hz, 2H), 6.11 (d, J = 6.2 Hz, 1H), 4.78 (d, J = 5.6 Hz, 1H), 1.71 (s, 9H);

13C NMR (126 MHz, CDCl3) δ 155.03, 145.54, 136.81, 134.71, 129.62, 129.43, 129.19, 119.64, 114.42, 61.95, 53.93, 30.29;

FT-IR (ATR) νmax/cm-1 3330.5, 3052.5, 2940.9, 1603.6, 1284.1;

HRMS (ESI+): m/z calcd. for C18H20ClN5 + 342.1480, found 342.1474

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