Production of chiral alcohols from racemic mixtures by integrated heterogeneous chemoenzymatic catalysis in fixed bed continuous operation

Abstract

Production of chiral alcohols from racemic mixtures with an integrated heterogeneous chemo-enzymatic two step relay catalyst in fixed bed continuous operation.

Optimized Immobilization Strategy for Dirhodium(II) Carboxylate Catalysts for C−H Functionalization and Their Implementation in a Packed Bed Flow Reactor

“…Although substrates 20 c and 20 d were obtained with lower yields (32 %a nd 25 %, respectively), ar elatively high enantioselectivity (82 % ee)w as maintained in both reactions.T hese low yields are presumably caused by the slower rate of diazo decomposition due to the presence of the strongly electron-withdrawing nitro group (20 c)a nd the coordination between the rhodium active site and the pyridine nitrogen (20 d)for these two substrates.The similarity in performance between the heterogeneous catalyst implemented in the packed bed flow reactor and the homogeneous catalyst employed in batch supports our previous hypothesis that the immobilization via the equatorial ring B is robust and may be broadly applied to other Rh 2 (TPCP) 4 -derived catalysts.Additionally,the weight hourly space velocity (WHSV) of our system is large (570 h À1 for substrates 20 a,b,e-i;2 85 h À1 for substrates 20 c,d)c ompared to some other reported supported catalysts for site-and enantioselective organic reactions. [17] This high WHSV and the low residence time (53 sfor substrates 20 a,b,e-i;106 sfor substrates 20 c,d)show that our system has an efficient use of catalyst and may be capable of achieving high productivity to enable the scale-up of this system.…”

“…Thep resence of two aryl bromides on the Rh 2 (S-2-Cl-5-BrTPCP) 3 (Br@B) catalyst presents as electivity issue that may result in al oss of control over the site of catalyst immobilization. Thus,wedecided to develop anew Rh 2 (S-2-Cl-5-BrTPCP) 4 analog with similar or better performance.T o do so,the bromide moiety on the o-Cl-aryl ring would need to be replaced by asubstituent with similar steric and electronic properties,b ut with no lability to Sonogashira coupling; hence,atrifluoromethyl group was proposed as areplacement functional group.T he new Rh 2 (S-2-Cl-5-CF 3 TPCP) 4 catalyst (17)w as synthesized (See Supporting Information for detailed synthesis) and subjected to the reference reaction with 1-bromo-4-pentylbenzene.T he performance of the new catalyst was found to be comparable in site-, diastereo-, enantioselectivity,a nd yield to that of the Rh 2 (S-2-Cl-5-BrTPCP) 4 catalyst ( Figure 6). Thus,t he Rh 2 (S-2-Cl-5-CF 3 TPCP) 4 was chosen as the optimal dirhodium catalyst for our flow reaction purposes and was subjected to immobilization on the platelet SBA-15 support via ring B.…”

Covalent Immobilization of Naringinase over Two‐Dimensional 2D Zeolites and its Applications in a Continuous Process to Produce Citrus Flavonoids and for Debittering of Juices

“…(Scheme S1) As consequence, this material presents high external surface area (∼600 m 2 g −1 ) containing regularly distributed silanol groups. Moreover, this material is highly stable in aqueous media that, together with their 2D structure, offers the possibility to act as excellent stable enzyme support for industrial biotransformations . In this work, we have immobilized a commercial naringinase ( denoted as crude) (from Penicillium decumbens) and a purified naringinase with high α‐L‐rhamnosidase activity (denoted as pure) over pure silica ITQ‐2 zeolite.…”

“…Moreover, this material is highly stable in aqueous media that, together with their 2D structure, offers the possibility to act as excellent stable enzyme support for industrial biotransformations. [29] In this work, we have immobilized a commercial naringinase ( denoted as crude) (from Penicillium decumbens) and a purified naringinase with high α-L-rhamnosidase activity (denoted as pure) over pure silica ITQ-2 zeolite. From the hydrolysis of naringin, the crude naringinase allow obtaining selectively the flavonoid naringenin, while the purified naringinase allow obtaining selectively the monoglycoside flavonoid prunin.…”

Recent Advances in Electrochemical Biosensors: Applications, Challenges, and Future Scope

“…The electrochemical biosensors consist of three electrodes, i.e., reference, counter, and working. The electron generated or consumed during the catalysis of enzymes is used for producing a signal that helps in the detection process [ 12 ]. These are further classified as potentiometric, amperometric, voltammetric, and impedimetric biosensors.…”