Organic Synthesis International: flow chemistry

Showing posts with label flow chemistry. Show all posts

Sunday 8 January 2017

Improving the efficiency of the Diels-Alder process by using flow chemistry and zeolite catalysis

Green Chem., 2017, 19,237-248
DOI: 10.1039/C6GC02334G, Paper

S. Seghers, L. Protasova, S. Mullens, J. W. Thybaut, C. V. Stevens
The industrial application of the Diels-Alder reaction for the synthesis of (hetero)cyclic compounds constitutes an important challenge. To tackle the reagent instability problems and corresponding safety issues, the use of a high-pressure and zeolite catalysed microreactor process is presented.

Improving the efficiency of the Diels–Alder process by using flow chemistry and zeolite catalysis

S. Seghers,^a L. Protasova,^b S. Mullens,^b J. W. Thybaut^c and C. V. Stevens*^a

*Corresponding authors

SynBioC Research Group, Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
E-mail: chris.stevens@ugent.be

VITO, Vlaamse Instelling voor Technologisch Onderzoek, Boeretang 200, 2400 Mol, Belgium

Laboratory for Chemical Technology, Department of Chemical Engineering and Technical Chemistry, Faculty of Engineering and Architecture, Ghent University, Technologiepark 914, 9052 Ghent, Belgium

Green Chem., 2017,19, 237-248

DOI: 10.1039/C6GC02334G

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC02334G?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

The industrial application of the Diels–Alder reaction for the atom-efficient synthesis of (hetero)cyclic compounds constitutes an important challenge. Safety and purity concerns, related to the instability of the polymerization prone diene and/or dienophile, limit the scalability of the production capacity of Diels–Alder products in a batch mode. To tackle these problems, the use of a high-pressure continuous microreactor process was considered. In order to increase the yields and the selectivity towards the endo-isomer, commercially available zeolites were used as a heterogeneous catalyst in a microscale packed bed reactor. As a result, a high conversion (≥95%) and endo-selectivity (89

11) were reached for the reaction of cyclopentadiene and methyl acrylate, using a 1

1 stoichiometry. A throughput of 0.87 g h⁻¹during at least 7 h was reached, corresponding to a 3.5 times higher catalytic productivity and a 14 times higher production of Diels–Alder adducts in comparison to the heterogeneous lab-scale batch process. Catalyst deactivation was hardly observed within this time frame. Moreover, complete regeneration of the zeolite was demonstrated using a straightforward calcination procedure.

//////Diels-Alder, flow chemistry, zeolite catalysis

Thursday 10 March 2016

Nanopalladium-catalyzed conjugate reduction of Michael acceptors - application in flow

Nanopalladium-catalyzed conjugate reduction of Michael acceptors - application in flow

Green Chem., 2016, Advance Article
DOI: 10.1039/C5GC02920A, Communication

Anuja Nagendiran, Henrik Sorensen, Magnus J. Johansson, Cheuk-Wai Tai, Jan-E. Backvall
A continuous-flow approach towards the selective nanopalladium-catalyzed hydrogenation of the olefinic bond in various Michael acceptors, which could lead to a greener and more sustainable process, has been developed.

A continuous-flow approach towards the selective nanopalladium-catalyzed hydrogenation of the olefinic bond in various Michael acceptors, which could lead to a greener and more sustainable process, has been developed. The nanopalladium is supported on aminofunctionalized mesocellular foam. Both aromatic and aliphatic substrates, covering a variation of functional groups such as acids, aldehydes, esters, ketones, and nitriles were selectively hydrogenated in high to excellent yields using two different flow-devices (H-Cube® and Vapourtec). The catalyst was able to hydrogenate cinnamaldehyde continuously for 24 h (in total hydrogenating 19 g cinnanmaldehyde using 70 mg of catalyst in the H-cube®) without showing any significant decrease in activity or selectivity. Furthermore, the metal leaching of the catalyst was found to be very low (ppb amounts) in the two flow devices

3 Gottlieb, H. E.; Kotlyar, V; Nudelman, A. J. Org. Chem. 1997, 62, 7512-7515.

Nanopalladium-catalyzed conjugate reduction of Michael acceptors – application in flow

Anuja Nagendiran,^a^b Henrik Sörensen,^b^c Magnus J. Johansson,^b^c Cheuk-Wai Tai^d and Jan-E. Bäckvall*^a^b

*Corresponding authors

^aDepartment of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
E-mail: jeb@organ.su.se

^bBerzelii Centre EXSELENT on Porous Materials, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden

^cAstraZeneca R&D, Innovative Medicines, Cardiovascular and Metabolic Disorders, Medicinal Chemistry, Pepparedsleden 1, SE-431 83 Mölndal, Sweden

^dDepartment of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden

Green Chem., 2016, Advance Article

DOI: 10.1039/C5GC02920A

http://pubs.rsc.org/en/Content/ArticleLanding/2016/GC/C5GC02920A?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

///////

Saturday 12 September 2015

Aerobic flow oxidation of alcohols in water catalyzed by platinum nanoparticles dispersed in an amphiphilic polymer

Osako, T.; Toriia, K.; Uozumi, Y.; Aerobic flow oxidation of alcohols in water catalyzed by platinum nanoparticles dispersed in an amphiphilic polymer; RSC Adv.; 2015; 5; 2647-2654

link to article

http://pubs.rsc.org/en/content/articlelanding/2015/ra/c4ra14947e#!divAbstract

We have developed a technique for the aqueous aerobic flow oxidation of alcohols in a continuous-flow reactor containing platinum nanoparticles dispersed on an amphiphilic polystyrene–poly(ethylene glycol) resin (ARP-Pt). Various primary and secondary alcohols including aliphatic, aromatic and heteroaromatic alcohols were efficiently oxidized within 73 seconds in a flowing aqueous system at 100–120 °C under 40–70 bar of the system pressure to give the corresponding carboxylic acids and ketones, respectively, in up to 99% yield. Benzaldehydes could be also prepared selectively from benzyl alcohols by conducting the flow oxidation under the standard conditions in the presence of triethylamine. Moreover, a practical gram-scale synthesis of surfactants was realized in the aqueous aerobic continuous flow oxidation for 36–116 hours. This aerobic flow oxidation system provides a safe, clean, green, rapid and efficient practical method for oxidizing alcohols.