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Prieschl M, Sedelmeier J, Püntener K, Hildbrand S, Williams JD, Kappe CO. Rediscovering Cyanogen Gas for Organic Synthesis: Formation of 2-Cyanothiazole Derivatives. J Org Chem 2023. [PMID: 37339330 DOI: 10.1021/acs.joc.3c01110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
The expeditious synthesis of an API building block, 2-cyanothiazole, from cyanogen gas and a readily available dithiane is reported. A previously undisclosed partially saturated intermediate is formed, which can be further functionalized and isolated by the acylation of the hydroxy group. Dehydration using trimethylsilyl chloride furnished 2-cyanothiazole, which could be further converted to the corresponding amidine. The sequence provided a 55% yield over 4 steps. We envision that this work will spark further interest in cyanogen gas as a reactive and cost-effective synthetic reagent.
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Affiliation(s)
- Michael Prieschl
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Joerg Sedelmeier
- Department of Process Chemistry & Catalysis, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Kurt Püntener
- Department of Process Chemistry & Catalysis, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Stefan Hildbrand
- Department of Process Chemistry & Catalysis, F. Hoffmann-La Roche Ltd, 4070 Basel, Switzerland
| | - Jason D Williams
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - C Oliver Kappe
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz, Austria
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2
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Nagy BS, Fu G, Hone CA, Kappe CO, Ötvös SB. Harnessing a Continuous-Flow Persulfuric Acid Generator for Direct Oxidative Aldehyde Esterifications. CHEMSUSCHEM 2023; 16:e202201868. [PMID: 36377674 PMCID: PMC10107610 DOI: 10.1002/cssc.202201868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/30/2022] [Indexed: 06/16/2023]
Abstract
Persulfuric acid is a well-known oxidant in various industrial-scale purification procedures. However, due to its tendency toward explosive decomposition, its usefulness in organic synthesis remained largely underexplored. Herein, a continuous in situ persulfuric acid generator was developed and applied for oxidative esterification of aldehydes under flow conditions. Sulfuric acid served as a readily available and benign precursor to form persulfuric acid in situ. By taking advantage of the continuous-flow generator concept, safety hazards were significantly reduced, whilst a robust and effective approach was ensured for direct transformations of aldehydes to valuable esters. The process proved useful for the transformation of diverse aliphatic as well as aromatic aldehydes, while its preparative capability was verified by the multigram-scale synthesis of a pharmaceutically relevant key intermediate. The present flow protocol demonstrates the safe, sustainable, and scalable application of persulfuric acid in a manner that would not be amenable to conventional batch processing.
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Affiliation(s)
- Bence S. Nagy
- Institute of ChemistryUniversity of GrazNAWI GrazHeinrichstrasse 28A-8010GrazAustria
| | - Gang Fu
- Institute of ChemistryUniversity of GrazNAWI GrazHeinrichstrasse 28A-8010GrazAustria
| | - Christopher A. Hone
- Institute of ChemistryUniversity of GrazNAWI GrazHeinrichstrasse 28A-8010GrazAustria
- Center for Continuous Flow Synthesis and Processing (CC FLOW)Research CenterPharmaceutical Engineering GmbH (RCPE)Inffeldgasse 13A-8010GrazAustria
| | - C. Oliver Kappe
- Institute of ChemistryUniversity of GrazNAWI GrazHeinrichstrasse 28A-8010GrazAustria
- Center for Continuous Flow Synthesis and Processing (CC FLOW)Research CenterPharmaceutical Engineering GmbH (RCPE)Inffeldgasse 13A-8010GrazAustria
| | - Sándor B. Ötvös
- Institute of ChemistryUniversity of GrazNAWI GrazHeinrichstrasse 28A-8010GrazAustria
- Center for Continuous Flow Synthesis and Processing (CC FLOW)Research CenterPharmaceutical Engineering GmbH (RCPE)Inffeldgasse 13A-8010GrazAustria
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3
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Kouznetsov VV, Hernández JG. Nanostructured silicate catalysts for environmentally benign Strecker-type reactions: status quo and quo vadis. RSC Adv 2022; 12:20807-20828. [PMID: 35919186 PMCID: PMC9299969 DOI: 10.1039/d2ra03102g] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/30/2022] [Indexed: 01/26/2023] Open
Abstract
Chemical processes are usually catalytic transformations. The use of catalytic reagents can reduce the reaction temperature, decrease reagent-based waste, and enhance the selectivity of a reaction potentially avoiding unwanted side reactions leading to green technology. Chemical processes are also frequently based on multicomponent reactions (MCRs) that possess evident improvements over multistep processes. Both MCRs and catalysis tools are the most valuable principles of green chemistry. Among diverse MCRs, the three-component Strecker reaction (S-3-CR) is a particular transformation conducive to the formation of valuable bifunctional building blocks (α-amino nitriles) in organic synthesis, medicinal chemistry, drug research, and organic materials science. To be a practical synthetic tool, the S-3-CR must be achieved using alternative energy input systems, safe reaction media, and effective catalysts. These latter reagents are now deeply associated with nanoscience and nanocatalysis. Continuously developed, nanostructured silicate catalysts symbolize green pathways in our quest to attain sustainability. Studying and developing nanocatalyzed S-3-CR condensations as an important model will be suitable for achieving the current green mission. This critical review aims to highlight the advances in the development of nanostructured catalysts for technologically important Strecker-type reactions and to analyze this progress from the viewpoint of green and sustainable chemistry.
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Affiliation(s)
- Vladimir V Kouznetsov
- Laboratorio de Química Orgánica y Biomolecular, CMN, Universidad Industrial de Santander, Parque Tecnológico Guatiguará Km 2 Vía Refugio, Piedecuesta 681011 Colombia +57 7 634 4000 ext. 3593
| | - José G Hernández
- Grupo Ciencia de los Materiales, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia Calle 70 No. 52-21 Medellín Colombia
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Bonner A, Loftus A, Padgham AC, Baumann M. Forgotten and forbidden chemical reactions revitalised through continuous flow technology. Org Biomol Chem 2021; 19:7737-7753. [PMID: 34549240 DOI: 10.1039/d1ob01452h] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Continuous flow technology has played an undeniable role in enabling modern chemical synthesis, whereby a myriad of reactions can now be performed with greater efficiency, safety and control. As flow chemistry furthermore delivers more sustainable and readily scalable routes to important target structures a growing number of industrial applications are being reported. In this review we highlight the impact of flow chemistry on revitalising important chemical reactions that were either forgotten soon after their initial report as necessary improvements were not realised due to a lack of available technology, or forbidden due to unacceptable safety concerns relating to the experimental procedure. In both cases flow processing in combination with further reaction optimisation has rendered a powerful set of tools that make such transformations not only highly efficient but moreover very desirable due to a more streamlined construction of desired scaffolds. This short review highlights important contributions from academic and industrial laboratories predominantly from the last 5 years allowing the reader to gain an appreciation of the impact of flow chemistry.
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Affiliation(s)
- Arlene Bonner
- School of Chemistry, University College Dublin, Science Centre South, D04 N2E5, Dublin, Ireland.
| | - Aisling Loftus
- School of Chemistry, University College Dublin, Science Centre South, D04 N2E5, Dublin, Ireland.
| | - Alex C Padgham
- School of Chemistry, University College Dublin, Science Centre South, D04 N2E5, Dublin, Ireland.
| | - Marcus Baumann
- School of Chemistry, University College Dublin, Science Centre South, D04 N2E5, Dublin, Ireland.
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Kiyokawa K, Urashima N, Minakata S. Tris(pentafluorophenyl)borane-Catalyzed Formal Cyanoalkylation of Indoles with Cyanohydrins. J Org Chem 2021; 86:8389-8401. [PMID: 34077225 DOI: 10.1021/acs.joc.1c00808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Despite the significant achievements related to the C3 functionalization of indoles, cyanoalkylation reactions continue to remain rather limited. We herein report on the formal C3 cyanoalkylation of indoles with cyanohydrins in the presence of a tris(pentafluorophenyl)borane (B(C6F5)3) catalyst. It is noteworthy that cyanohydrins are used as a cyanoalkylating reagent in the present reaction, even though they are usually used as only a HCN source. Mechanistic investigations revealed the unique reactivity of the B(C6F5)3 catalyst in promoting the decomposition of a cyanohydrin by a Lewis acidic activation through the coordination of the cyano group to the boron center. In addition, a catalytic three-component reaction using indoles, aldehydes as a carbon unit, and acetone cyanohydrin that avoids the discrete preparation of each aldehyde-derived cyanohydrin is also reported. The developed methods provide straightforward, highly efficient, and atom-economic access to various types of synthetically useful indole-3-acetonitrile derivatives containing α-tertiary or quaternary carbon centers.
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Affiliation(s)
- Kensuke Kiyokawa
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
| | - Naruyo Urashima
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
| | - Satoshi Minakata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
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Hone CA, Kappe CO. Membrane Microreactors for the On-Demand Generation, Separation, and Reaction of Gases. Chemistry 2020; 26:13108-13117. [PMID: 32515835 PMCID: PMC7692882 DOI: 10.1002/chem.202001942] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 06/08/2020] [Indexed: 11/25/2022]
Abstract
The use of gases as reagents in organic synthesis can be very challenging, particularly at a laboratory scale. This Concept takes into account recent studies to make the case that gases can indeed be efficiently and safely formed from relatively inexpensive commercially available reagents for use in a wide range of organic transformations. In particular, we argue that the exploitation of continuous flow membrane reactors enables the effective separation of the chemistry necessary for gas formation from the chemistry for gas consumption, with these two stages often containing incompatible chemistry. The approach outlined eliminates the need to store and transport excessive amounts of potentially toxic, reactive or explosive gases. The on‐demand generation, separation and reaction of a number of gases, including carbon monoxide, diazomethane, trifluoromethyl diazomethane, hydrogen cyanide, ammonia and formaldehyde, is discussed.
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Affiliation(s)
- Christopher A Hone
- Center for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010, Graz, Austria.,Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010, Graz, Austria
| | - C Oliver Kappe
- Center for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010, Graz, Austria.,Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010, Graz, Austria
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7
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Dallinger D, Gutmann B, Kappe CO. The Concept of Chemical Generators: On-Site On-Demand Production of Hazardous Reagents in Continuous Flow. Acc Chem Res 2020; 53:1330-1341. [PMID: 32543830 PMCID: PMC7467564 DOI: 10.1021/acs.accounts.0c00199] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
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In recent years, a steadily growing number of chemists, from both
academia and industry, have dedicated their research to the development
of continuous flow processes performed in milli- or microreactors.
The common availability of continuous flow equipment at virtually
all scales and affordable cost has additionally impacted this trend.
Furthermore, regulatory agencies such as the United States Food and
Drug Administration actively encourage continuous manufacturing of
active pharmaceutical ingredients (APIs) with the vision of quality
and productivity improvements. That is why the pharmaceutical industry
is progressively implementing continuous flow technologies. As a result
of the exceptional characteristics of continuous flow reactors such
as small reactor volumes and remarkably fast heat and mass transfer,
process conditions which need to be avoided in conventional batch
syntheses can be safely employed. Thus, continuous operation is particularly
advantageous for reactions at high temperatures/pressures (novel process
windows) and for ultrafast, exothermic reactions (flash chemistry). In addition to conditions that are outside of the operation range
of conventional stirred tank reactors, reagents possessing a high
hazard potential and therefore not amenable to batch processing can
be safely utilized (forbidden chemistry). Because of the small reactor
volumes, risks in case of a failure are minimized. Such hazardous
reagents often are low molecular weight compounds, leading generally
to the most atom-, time-, and cost-efficient route toward the desired
product. Ideally, they are generated from benign, readily available
and cheap precursors within the closed environment of the flow reactor
on-site on-demand. By doing so, the transport, storage, and handling
of those compounds, which impose a certain safety risk especially
on a large scale, are circumvented. This strategy also positively
impacts the global supply chain dependency, which can be a severe
issue, particularly in times of stricter safety regulations or an
epidemic. The concept of the in situ production of a hazardous material
is generally referred to as the “generator” of the material.
Importantly, in an integrated flow process, multiple modules can be
assembled consecutively, allowing not only an in-line purification/separation
and quenching of the reagent, but also its downstream conversion to
a nonhazardous product. For the past decade, research in our
group has focused on the continuous
generation of hazardous reagents using a range of reactor designs
and experimental techniques, particularly toward the synthesis of
APIs. In this Account, we therefore introduce chemical generator concepts
that have been developed in our laboratories for the production of
toxic, explosive, and short-lived reagents. We have defined three
different classes of generators depending on the reactivity/stability
of the reagents, featuring reagents such as Br2, HCN, peracids,
diazomethane (CH2N2), or hydrazoic acid (HN3). The various reactor designs, including in-line membrane
separation techniques and real-time process analytical technologies
for the generation, purification, and monitoring of those hazardous
reagents, and also their downstream transformations are presented.
This Account should serve as food for thought to extend the scope
of chemical generators for accomplishing more efficient and more economic
processes.
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Affiliation(s)
- Doris Dallinger
- Center for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Bernhard Gutmann
- Center for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - C. Oliver Kappe
- Center for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
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Spano MB, Tran BH, Majumdar S, Weiss GA. 3D-Printed Labware for High-Throughput Immobilization of Enzymes. J Org Chem 2020; 85:8480-8488. [PMID: 32502347 PMCID: PMC9096805 DOI: 10.1021/acs.joc.0c00789] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In continuous flow biocatalysis, chemical transformations can occur under milder, greener, more scalable, and safer conditions than conventional organic synthesis. However, the method typically involves extensive screening to optimize each enzyme's immobilization on its solid support material. The task of weighing solids for large numbers of experiments poses a bottleneck for screening enzyme immobilization conditions. For example, screening conditions often require multiple replicates exploring different support chemistries, buffer compositions, and temperatures. Thus, we report 3D-printed labware designed to measure and handle solids in multichannel format and expedite screening of enzyme immobilization conditions. To demonstrate the generality of these advances, alkaline phosphatase, glucose dehydrogenase, and laccase were screened for immobilization efficiency on seven resins. The results illustrate the requirements for optimization of each enzyme's loading and resin choice for optimal catalytic performance. Here, 3D-printed labware can decrease the requirements for an experimentalist's time by >95%. The approach to rapid optimization of enzyme immobilization is applicable to any enzyme and many solid support resins. Furthermore, the reported devices deliver precise and accurate aliquots of essentially any granular solid material.
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Affiliation(s)
- Michael B. Spano
- Department of Chemistry, University of California, Irvine, California, 92697-2025, United States of America
| | - Brandan H. Tran
- Department of Chemistry, University of California, Irvine, California, 92697-2025, United States of America
| | - Sudipta Majumdar
- Department of Chemistry, University of California, Irvine, California, 92697-2025, United States of America
| | - Gregory A. Weiss
- Department of Chemistry, University of California, Irvine, California, 92697-2025, United States of America
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697-3900, United States of America
- Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697-3958, United States of America
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Demaerel J, Veryser C, De Borggraeve WM. Ex situ gas generation for lab scale organic synthesis. REACT CHEM ENG 2020. [DOI: 10.1039/c9re00497a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This review discusses recent examples of ex situ generated gaseous reagents, and their use in organic synthesis.
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Affiliation(s)
- Joachim Demaerel
- Molecular Design and Synthesis
- Department of Chemistry
- 3001 Leuven
- Belgium
| | - Cedrick Veryser
- Molecular Design and Synthesis
- Department of Chemistry
- 3001 Leuven
- Belgium
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