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

• ; microreactor; monolith; palladium; Suzuki–Miyaura reaction; Introduction Functionalized solid supports like polymers loaded with homogeneous catalysts are well established in organic synthesis [1][2][3][4]. Simple purification of the products and easy recyclability of the catalysts are major advantages of

• that the resin can only swell inside the glass while the glass monolith provides a stable rod-like shape inside the microreactor. The Merrifield-type resin was aminated to yield polyionic support 1. This polymer serves as an anchor to leave the metal species (sodium tetrachloropalladate; Na2PdCl4) in

• -bound ammonium species [23][24][25][26][27][28][29]. These functionalized composite Raschig-rings are incorporated inside the flow microreactor which has a dead volume of about 1–2 mL (Figure 1) [30]. We could show that the palladium clusters are composed of palladium nanoparticles. Particle sizes

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

• of benzaldehyde (1) catalyzed by lanthanide(III)-PyBox complexes was investigated using a T-shaped borosilicate microreactor and electroosmotic flow (Scheme 1) [12]. The reaction was initially screened with different lanthanide (III) complexes such as Ce(III), Yb(III) and Lu(III). Further efforts

• observed to be higher in the microreactor. A single-channel, falling film microreactor designed specifically for efficient gas-liquid phase contact was used to screen the asymmetric hydrogenation of (Z)-methyl acetamidocinnamate 4 and related substrates (Scheme 2) [13][14]. Seventeen chiral phosphines were

• screened for reactivity and enantioselectivity with the rhodium catalyst [Rh(COD)2]BF4 within a 3 min residence time. With this device, very low catalyst/ligand loadings were used per run (ca. 0.1 μg of Rh catalyst), providing reliably reproducible results. Reactivity in the microreactor was found to be

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

• characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol

• entered the reactor as plugs but merged into an emulsion on the packed-bed. The emulsion coalesced into larger plugs upon exiting the reactor, leaving the organic product separate from the aqueous by-products. Furthermore, the microreactor oxidized a wide range of alcohols and remained active in excess of

• higher degree of safety [1][2][3][4][5][6][7][8][9][10][11][12]. Alcohol oxidations are well suited for microreactors due to high by-product formation, catalyst contamination and safety concerns often associated with scale-up in batch reactors [13]. Recent developments in microreactor technology and