Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations

• Ram Awatar Maurya,
• Chan Pil Park and
• Dong-Pyo Kim

Beilstein J. Org. Chem. 2011, 7, 1158–1163, doi:10.3762/bjoc.7.134

• efficient heat dissipation, and the capability of spatial and temporal control of the reagents or products. These advantages have been exploited for various purposes such as performing selective reactions with highly unstable intermediates [24][25], improving heterogeneous catalysis [26][27][28][29], multi

Nano copper oxide catalyzed synthesis of symmetrical diaryl sulfides under ligand free conditions

• K. Harsha Vardhan Reddy,
• V. Prakash Reddy,
• A. Ashwan Kumar,
• G. Kranthi and
• Y.V.D. Nageswar

Beilstein J. Org. Chem. 2011, 7, 886–891, doi:10.3762/bjoc.7.101

• , especially under ligand-free conditions, for the synthesis of such highly useful organic compounds. In the past few years, considerable efforts have been made in the area of heterogeneous catalysis for various organic transformations. In general, heterogeneous catalysts offer higher surface area and lower

• coordinating sites, which are responsible for their higher catalytic activity [45][46][47]. Furthermore, heterogeneous catalysis has the advantage of high atom efficiency, easy product purification, and reusability of the catalyst. However, up until now, the investigation of nanoparticles as catalysts has been

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• -2,4-hexadiene (7) in moderate yields when either AuI3 or AuCN were used as catalysts (Scheme 1, reaction 2). Only four years later, de Meijere reported a gold-catalyzed rearrangement of strained small ring hydrocarbons [12]. Although heterogeneous catalysis seemed to be operating in this case

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed. Keywords: flow chemistry; heterogeneous catalysis; microreactors; palladium; process

Air-stable, recyclable, and time-efficient diphenylphosphinite cellulose-supported palladium nanoparticles as a catalyst for Suzuki–Miyaura reactions

• Qingwei Du and
• Yiqun Li

Beilstein J. Org. Chem. 2011, 7, 378–385, doi:10.3762/bjoc.7.48

• obtained in good to excellent yield under mild reaction conditions. Moreover, the catalyst could be easily recovered by simple filtration and reused for at least 6 cycles without losing its activity. Keywords: diphenylphosphinite cellulose; heterogeneous catalysis; nanopalladium; polymer-supported

Studies on Pd/NiFe₂O₄ catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

• Sanjay R. Borhade and
• Suresh B. Waghmode

Beilstein J. Org. Chem. 2011, 7, 310–319, doi:10.3762/bjoc.7.41

• arylboronic acids. The reaction gave excellent yields (70–98%) under ligand free conditions in a 1:1 DMF/H2O solvent mixture, in short reaction times (10–60 min). The catalyst could be recovered easily by applying an external magnetic field. The polyaryls were similarly synthesized. Keywords: heterogeneous

• catalysis; nickel ferrite; polyaryls; Suzuki reaction; terphenyls; Introduction Recently, transition metal catalyzed cross-coupling protocols have generated immense interest owing to their versatile applications in organic synthesis [1][2][3][4]. The Pd catalyzed Suzuki reaction between aryl halides with

ROMP-Derived cyclooctene-based monolithic polymeric materials reinforced with inorganic nanoparticles for applications in tissue engineering

• Franziska Weichelt,
• Solvig Lenz,
• Stefanie Tiede,
• Ingrid Reinhardt,
• Bernhard Frerich and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, 1199–1205, doi:10.3762/bjoc.6.137

• well as heterogeneous catalysis [16][17][18]. Generally, cyclooctene-derived monoliths differ from their NBE-based counterparts in that they are less prone to oxidation and display higher elastic moduli. With the aim to synthesize organic-inorganic monolithic hybrid materials for application as

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

• Guangming Nan,
• Fang Ren and
• Meiming Luo

Beilstein J. Org. Chem. 2010, 6, No. 70, doi:10.3762/bjoc.6.70

• general study on the Suzuki–Miyaura reactions of 1-aryltriazenes under heterogeneous catalysis described to date. Previously, we reported an active and recyclable polystyrene-supported Pd–NHC (N-heterocyclic carbene) catalyst 1 (Scheme 1) for the Suzuki–Miyaura cross-coupling reactions of aryl bromides

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

• Gajanan M. Pawar,
• Jochen Weckesser,
• Siegfried Blechert and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, No. 28, doi:10.3762/bjoc.6.28

• micellar catalytic set up are discussed. Keywords: block copolymers; catalysis; hydrophilic polymers; metathesis; micelles; Introduction Catalysts bound to amphiphilic block copolymers find increasing use in micellar catalysis since they combine the advantages of both homogeneous and heterogeneous

• catalysis in one system. Thus, with catalysts permanently linked to the block copolymer, metal leaching is substantially reduced and allows for the separation/reuse of the catalyst [1][2][3][4][5][6][7]. In cases where reactions are run in polar media, the catalyst is best located inside the hydrophobic

Hydroxyapatite supported caesium carbonate as a new recyclable solid base catalyst for the Knoevenagel condensation in water

• Monika Gupta,
• Rajive Gupta and
• Medha Anand

Beilstein J. Org. Chem. 2009, 5, No. 68, doi:10.3762/bjoc.5.68

• . Thus, the use of aqueous solvents in chemical reactions has proved a cleaner and safer alternative to organic solvents [2]. Heterogeneous catalysis, which has the immediate advantage of easy recoverability and recyclability of the catalyst – sometimes with the further advantage of increased selectivity

Polyionic polymers – heterogeneous media for metal nanoparticles as catalyst in Suzuki–Miyaura and Heck–Mizoroki reactions under flow conditions

• Klaas Mennecke and
• Andreas Kirschning

Beilstein J. Org. Chem. 2009, 5, No. 21, doi:10.3762/bjoc.5.21

• heterogeneous supports for palladium(0) nanoparticles is described. These functionalized polymers were incorporated inside a flow reactor and employed in Suzuki–Miyaura and Heck cross couplings under continuous flow conditions. Keywords: Heck–Mizoroki reaction; heterogeneous catalysis; ion exchange resin

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• conditions and in the case of heterogeneous catalysis, potential long term use of the catalysts. This review will highlight some of the continuous flow asymmetric reactions described to date. Review Homogeneous catalysis Only a few examples of homogeneous enantioselective reactions in continuous flow have

• as donor, and subsequently to a Mannich reaction with α-iminoglyoxylate. Supported and heterogeneous catalysis Chiral catalysts and ligands are often expensive and the complete separation of these components from reaction products can frequently be quite challenging. Degradation products and leaching

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed- bed microreactor

• Andrew Bogdan and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2009, 5, No. 17, doi:10.3762/bjoc.5.17

• 100 trials without showing any loss of catalytic activity. Keywords: alcohol oxidation; flow chemistry; heterogeneous catalysis; microreactors; TEMPO; Introduction Microreactors have gained attention because they can help run chemical transformations more efficiently, more selectively, and with a