scholarly journals Breaking Molecular Symmetry through Biocatalytic Reactions to Gain Access to Valuable Chiral Synthons

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1454
Author(s):  
Angela Patti ◽  
Claudia Sanfilippo
Keyword(s):  
Bioactive Compounds ◽  
Continuous Flow ◽  
Molecular Diversity ◽  
Molecular Symmetry ◽  
Flow Conditions ◽  
Reaction Conditions ◽  
Whole Cells ◽  
Efficient Approach ◽  
Substrate Tolerance ◽  
Gain Access

In this review the recent reports of biocatalytic reactions applied to the desymmetrization of meso-compounds or symmetric prochiral molecules are summarized. The survey of literature from 2015 up to date reveals that lipases are still the most used enzymes for this goal, due to their large substrate tolerance, stability in different reaction conditions and commercial availability. However, a growing interest is focused on the use of other purified enzymes or microbial whole cells to expand the portfolio of exploitable reactions and the molecular diversity of substrates to be transformed. Biocatalyzed desymmetrization is nowadays recognized as a reliable and efficient approach for the preparation of pharmaceuticals or natural bioactive compounds and many processes have been scaled up for multigram preparative purposes, also in continuous-flow conditions.

scholarly journals The Eschenmoser coupling reaction under continuous-flow conditions

2011 ◽  
Vol 7 ◽  
pp. 1164-1172 ◽  
Author(s):  
Sukhdeep Singh ◽  
J Michael Köhler ◽  
Andreas Schober ◽  
G Alexander Groß
Keyword(s):  
Continuous Flow ◽  
Elevated Temperatures ◽  
Reaction Times ◽  
Coupling Reaction ◽  
Flow Chemistry ◽  
Flow Conditions ◽  
Reaction Conditions ◽  
Bond Forming ◽  
Carbon Carbon Bond ◽  
Reaction Proceeds

The Eschenmoser coupling is a useful carbon–carbon bond forming reaction which has been used in various different synthesis strategies. The reaction proceeds smoothly if S-alkylated ternary thioamides or thiolactames are used. In the case of S-alkylated secondary thioamides or thiolactames, the Eschenmoser coupling needs prolonged reaction times and elevated temperatures to deliver valuable yields. We have used a flow chemistry system to promote the Eschenmoser coupling under enhanced reaction conditions in order to convert the demanding precursors such as S-alkylated secondary thioamides and thiolactames in an efficient way. Under pressurized reaction conditions at about 220 °C, the desired Eschenmoser coupling products were obtained within 70 s residence time. The reaction kinetics was investigated and 15 examples of different building block combinations are given.

scholarly journals Dimeric cyclobutane formation under continuous flow conditions using organophotoredox catalysed [2+2]-cycloaddition

2021 ◽  
Author(s):  
Helena Grantham ◽  
Marc Kimber
Keyword(s):  
Natural Products ◽  
Continuous Flow ◽  
Reaction Times ◽  
Functional Materials ◽  
Synthetic Route ◽  
Flow Conditions ◽  
Reaction Conditions ◽  
New Class ◽  
Cyclobutane Dimers ◽  
Flow Study

Radical cation-initiated dimerization of electron rich alkenes is an expedient method for the synthesis of cyclobutanes. By merging organophotoredox catalysis and continuous flow technology a batch versus continuous flow study has been performed providing a convenient synthetic route to an important carbazole cyclobutane material dimer t-DCzCB using less only 0.1 mol% of an organophotoredox catalyst. The scope of this methodology was explored giving a new class of functional materials, as well as an improved synthetic route to styrene based lignan dimeric natural products. The cyclobutane dimers could be isolated in higher chemical yields under continuous flow conditions and reaction times were reduced significantly compared to traditional batch reaction conditions.

Photodecarboxylative Benzylations of N-Methoxyphthalimide under Batch and Continuous-Flow Conditions

2015 ◽  
Vol 68 (11) ◽  
pp. 1662 ◽  
Author(s):  
Hossein Mohammadkhani Pordanjani ◽  
Christian Faderl ◽  
Jun Wang ◽  
Cherie A. Motti ◽  
Peter C. Junk ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Methoxy Group ◽  
Irradiation Time ◽  
Batch Process ◽  
Flow Conditions ◽  
Reaction Conditions

A series of photodecarboxylative benzylations of N-methoxyphthalimide were successfully realised using easily accessible starting materials. The reactions proceeded smoothly and the corresponding benzylated hydroxyphthalimidines were obtained in moderate to good yields of 52–73 %. No competing photoinduced dealkoxylation of the N-methoxy group was observed. The reaction with potassium phenylacetate was subsequently investigated in an advanced continuous-flow photoreactor. The reactor allowed rapid optimization of the reaction conditions and gave the desired benzylated product in higher yield and shorter irradiation time compared with the batch process.

Exploiting photooxygenations mediated by porphyrinoid photocatalysts under continuous flow conditions

RSC Advances ◽  
2016 ◽  
Vol 6 (16) ◽  
pp. 12717-12725 ◽  
Author(s):  
Kleber T. de Oliveira ◽  
L. Zane Miller ◽  
D. Tyler McQuade
Keyword(s):  
Continuous Flow ◽  
Flow Conditions ◽  
Reaction Conditions ◽  
Long Term Experiments

Photooxygenations of naphthols under continuous flow conditions using porphyrinoids as photocatalysts are described. Reaction conditions, long-term experiments and scope were performed, thus allowing the production of substituted naphthoquinones.

scholarly journals A Continuous-Flow, Two-Step, Metal-Free Process for the Synthesis of Differently Substituted Chiral 1,2-Diamino Derivatives

Synthesis ◽  
2018 ◽  
Vol 50 (07) ◽  
pp. 1430-1438
Author(s):  
Maurizio Benaglia ◽  
Margherita Pirola ◽  
Maria Compostella ◽  
Laura Raimondi ◽  
Alessandra Puglisi
Keyword(s):  
Continuous Flow ◽  
Catalytic Synthesis ◽  
Flow Conditions ◽  
Reaction Conditions ◽  
Flow Process ◽  
Preliminary Screening ◽  
Metal Free ◽  
Free Process ◽  
Continuous Flow Process ◽  
Nitro Reduction

The enantioselective organocatalytic reduction of aryl-substituted nitroenamines was successfully performed under continuous-flow conditions. After a preliminary screening with a 10-μL microreactor, to establish the best reaction conditions, the reduction was scaled up in a 0.5-mL mesoreactor, without appreciable loss of enantioselectivity, that remained constantly higher than 90%. The in-flow nitro reduction was also accomplished, either by Raney nickel catalyzed hydrogenation or by a metal-free methodology based on the use of the very inexpensive and readily available reducing agent trichlorosilane. The final aim is to develop a two-step, continuous-flow process for the stereo­selective, metal-free, catalytic synthesis of differently functionalized chiral 1,2-diamines.

Metal–organic frameworks for the removal of the emerging contaminant atenolol under real conditions

2021 ◽  
Vol 50 (7) ◽  
pp. 2493-2500
Author(s):  
Sara Rojas ◽  
Jorge A. R. Navarro ◽  
Patricia Horcajada
Keyword(s):  
Continuous Flow ◽  
Metal Organic Frameworks ◽  
Fixed Bed ◽  
Emerging Contaminant ◽  
Flow Conditions ◽  
Metal Organic ◽  
Fixed Bed System

A defective Metal-Organic Frameworks as an improved material for the construction of a fixed-bed system working under continuous flow conditions for the removal of the emerging contaminant atenolol.

scholarly journals Formation and Utility of Reactive Ketene Intermediates Under Continuous Flow Conditions

Tetrahedron ◽  
2021 ◽  
pp. 132305
Author(s):  
Harry R. Smallman ◽  
Jamie A. Leitch ◽  
Tom McBride ◽  
Steven V. Ley ◽  
Duncan L. Browne
Keyword(s):  
Continuous Flow ◽  
Flow Conditions

scholarly journals Achieving selectivity in porphyrin bromination through a DoE-driven optimization under continuous flow conditions

2020 ◽  
Author(s):  
Paolo Zardi ◽  
Michele Maggini ◽  
Tommaso Carofiglio
Keyword(s):  
Reaction Time ◽  
Design Of Experiment ◽  
Continuous Flow ◽  
Optimization Process ◽  
Porphyrin Ring ◽  
Flow Conditions ◽  
Reaction Parameters ◽  
Synthetic Procedure ◽  
Relevant Factors ◽  
Post Functionalization

AbstractThe post-functionalization of porphyrins through the bromination in β position of the pyrrolic rings is a relevant transformation because the resulting bromoderivatives are useful synthons to covalently link a variety of chemical architectures to a porphyrin ring. However, single bromination of porphyrins is a challenging reaction for the abundancy of reactive β-pyrrolic positions in the aromatic macrocycle. We herein report a synthetic procedure for the efficient preparation of 2-bromo-5,10,15,20-tetraphenylporphyrin (1) under continuous flow conditions. The use of flow technology allows to reach an accurate control over critical reaction parameters such as temperature and reaction time. Furthermore, by performing the optimization process through a statistical DoE (Design of Experiment) approach, these parameters could be properly adjusted with a limited number of experiments. This process led us to a better understanding of the relevant factors that govern porphyrins monobromination and to obtain compound 1 with an unprecedent 80% yield.

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