A Systems Approach towards an Intelligent and Self‐Controlling Platform for Integrated Continuous Reaction Sequences

Continuous and autonomous-flow separation of laccase enzyme utilizing functionalized aqueous two-phase system with computer vision control

Downstream processing of biomolecules, particularly therapeutic proteins and enzymes, presents a formidable challenge due to intricate unit operations and high costs. This study introduces a novel cysteine (cys) functionalized aqueous two-phase system (ATPS) utilizing polyethylene glycol (PEG) and potassium phosphate, referred as PEG-K3PO4/cys, for selective extraction of laccase from complex protein mixtures. A 3D-baffle micro-mixer and phase separator was meticulously designed and equipped with computer vision controller, to enable precise mixing and continuous phase separation under automated-flow. Microfluidic-assisted ATPS exhibits substantial increase in partition coefficient (Kflow = 16.3) and extraction efficiency (EEflow = 88 %) for laccase compared to conventional batch process. Integrated and continuous-flow process efficiently partitioned laccase, even in low concentrations and complex crude extracts. Circular dichroism spectra of laccase confirm structural stability of enzyme throughout the purification process. Eventually, continuous-flow microfluidic bioseparation is highly useful for seamless downstream processing of target biopharmaceuticals in integrated and autonomous manner.

Recent advances in catalytic asymmetric synthesis

Asymmetric catalysis stands at the forefront of modern chemistry, serving as a cornerstone for the efficient creation of enantiopure chiral molecules characterized by their high selectivity. In this review, we delve into the realm of asymmetric catalytic reactions, which spans various methodologies, each contributing to the broader landscape of the enantioselective synthesis of chiral molecules. Transition metals play a central role as catalysts for a wide range of transformations with chiral ligands such as phosphines, N-heterocyclic carbenes (NHCs), etc., facilitating the formation of chiral C-C and C-X bonds, enabling precise control over stereochemistry. Enantioselective photocatalytic reactions leverage the power of light as a driving force for the synthesis of chiral molecules. Asymmetric electrocatalysis has emerged as a sustainable approach, being both atom-efficient and environmentally friendly, while offering a versatile toolkit for enantioselective reductions and oxidations. Biocatalysis relies on nature's most efficient catalysts, i.e., enzymes, to provide exquisite selectivity, as well as a high tolerance for diverse functional groups under mild conditions. Thus, enzymatic optical resolution, kinetic resolution and dynamic kinetic resolution have revolutionized the production of enantiopure compounds. Enantioselective organocatalysis uses metal-free organocatalysts, consisting of modular chiral phosphorus, sulfur and nitrogen components, facilitating remarkably efficient and diverse enantioselective transformations. Additionally, unlocking traditionally unreactive C-H bonds through selective functionalization has expanded the arsenal of catalytic asymmetric synthesis, enabling the efficient and atom-economical construction of enantiopure chiral molecules. Incorporating flow chemistry into asymmetric catalysis has been transformative, as continuous flow systems provide precise control over reaction conditions, enhancing the efficiency and facilitating optimization. Researchers are increasingly adopting hybrid approaches that combine multiple strategies synergistically to tackle complex synthetic challenges. This convergence holds great promise, propelling the field of asymmetric catalysis forward and facilitating the efficient construction of complex molecules in enantiopure form. As these methodologies evolve and complement one another, they push the boundaries of what can be accomplished in catalytic asymmetric synthesis, leading to the discovery of novel, highly selective transformations which may lead to groundbreaking applications across various industries.

From Platform to Knowledge Graph: Evolution of Laboratory Automation

High-fidelity computer-aided experimentation is becoming more accessible with the development of computing power and artificial intelligence tools. The advancement of experimental hardware also empowers researchers to reach a level of accuracy that was not possible in the past. Marching toward the next generation of self-driving laboratories, the orchestration of both resources lies at the focal point of autonomous discovery in chemical science. To achieve such a goal, algorithmically accessible data representations and standardized communication protocols are indispensable. In this perspective, we recategorize the recently introduced approach based on Materials Acceleration Platforms into five functional components and discuss recent case studies that focus on the data representation and exchange scheme between different components. Emerging technologies for interoperable data representation and multi-agent systems are also discussed with their recent applications in chemical automation. We hypothesize that knowledge graph technology, orchestrating semantic web technologies and multi-agent systems, will be the driving force to bring data to knowledge, evolving our way of automating the laboratory.

Regioselective Magnesiations and Zincations of Aromatics and Heterocycles Triggered by Lewis Acids

Mixed TMP‐bases (TMP=2,2,6,6‐tetramethylpiperidyl), such as TMPMgCl ⋅ LiCl, TMP₂Mg ⋅ 2LiCl, TMPZnCl ⋅ LiCl and TMP₂Zn ⋅ 2LiCl, are outstanding reagents for the metalation of functionalized aromatics and heterocycles. In the presence of Lewis acids, such as BF₃ ⋅ OEt₂ or MgCl₂, the metalation scope of such bases was dramatically increased, and regioselectivity switches were achieved in the presence or absence of these Lewis acids. Furthermore, highly reactive lithium bases, such as TMPLi or Cy₂NLi, are also compatible with various Lewis acids, such as MgCl₂ ⋅ 2LiCl, ZnCl₂ ⋅ 2LiCl or CuCN ⋅ 2LiCl. Performing such metalations in continuous flow using commercial setups permitted practical and convenient reaction conditions.

Reactor design and selection for effective continuous manufacturing of pharmaceuticals

Pharmaceutical production remains one of the last industries that predominantly uses batch processes, which are inefficient and can cause drug shortages due to the long lead times or quality defects. Consequently, pharmaceutical companies are transitioning away from outdated batch lines, in large part motivated by the many advantages of continuous manufacturing (e.g., low cost, quality assurance, shortened lead time). As chemical reactions are fundamental to any drug production process, the selection of reactor and its design are critical to enhanced performance such as improved selectivity and yield. In this article, relevant theories, and models, as well as their required input data are summarized to assist the reader in these tasks, focusing on continuous reactions. Selected examples that describe the application of plug flow reactors (PFRs) and continuous-stirred tank reactors (CSTRs)-in-series within the pharmaceutical industry are provided. Process analytical technologies (PATs), which are important tools that provide real-time in-line continuous monitoring of reactions, are recommended to be considered during the reactor design process (e.g., port design for the PAT probe). Finally, other important points, such as density change caused by thermal expansion or solid precipitation, clogging/fouling, and scaling-up, are discussed.

Advanced Real-Time Process Analytics for Multistep Synthesis in Continuous Flow*

In multistep continuous flow chemistry, studying complex reaction mixtures in real time is a significant challenge, but provides an opportunity to enhance reaction understanding and control. We report the integration of four complementary process analytical technology tools (NMR, UV/Vis, IR and UHPLC) in the multistep synthesis of an active pharmaceutical ingredient, mesalazine. This synthetic route exploits flow processing for nitration, high temperature hydrolysis and hydrogenation reactions, as well as three inline separations. Advanced data analysis models were developed (indirect hard modeling, deep learning and partial least squares regression), to quantify the desired products, intermediates and impurities in real time, at multiple points along the synthetic pathway. The capabilities of the system have been demonstrated by operating both steady state and dynamic experiments and represents a significant step forward in data-driven continuous flow synthesis.

Application of reactor engineering concepts in continuous flow chemistry: a review

The adoption of flow technology for the manufacture of chemical entities, and in particular pharmaceuticals, has seen rapid growth over the past two decades with the technology now blurring the lines between chemistry and chemical engineering.

A Practical Method for Continuous Production of sp3-Rich Compounds from (Hetero)Aryl Halides and Redox-Active Esters

A practically useful coupling reaction between aromatic halides and redox-active esters was realized by nickel catalysis through the use of a packed zinc bed column in continuous flow. Multiple reuse of the column showed a negligible decrease in efficiency, affording high space/time yields. A wide range of substrates, including a number of heteroaryl halides and polyfunctional materials were coupled in generally good yields. Longer-time and larger-scale experiments further demonstrates the robustness of the system.

The Molecular Industrial Revolution: Automated Synthesis of Small Molecules

Today we are poised for a transition from the highly customized crafting of specific molecular targets by hand to the increasingly general and automated assembly of different types of molecules with the push of a button. Creating machines that are capable of making many different types of small molecules on demand, akin to that which has been achieved on the macroscale with 3D printers, is challenging. Yet important progress is being made toward this objective with two complementary approaches: 1) Automation of customized synthesis routes to different targets by machines that enable the use of many reactions and starting materials, and 2) automation of generalized platforms that make many different targets using common coupling chemistry and building blocks. Continued progress in these directions has the potential to shift the bottleneck in molecular innovation from synthesis to imagination, and thereby help drive a new industrial revolution on the molecular scale.

Efficient kinetic experiments in continuous flow microreactors

Transient temperature and flowrates in continuous flow reaction systems allows for the rapid generation of kinetic data.

Barbier Continuous Flow Preparation and Reactions of Carbamoyllithiums for Nucleophilic Amidation

An ambient temperature continuous flow method for nucleophilic amidation and thioamidation is described. Deprotonation of formamides by lithium diisopropylamine (LDA) affords carbamoyllithium intermediates that are quenched in situ with various electrophiles such as ketones, allyl bromides, Weinreb and morpholino amides. The nature of the reactive lithium intermediates and the thermodynamics of the metalation were further investigated by ab initio calculations and kinetic experiments.

A Rapid Total Synthesis of Ciprofloxacin Hydrochloride in Continuous Flow

Within a total residence time of 9 min, the sodium salt of ciprofloxacin was prepared from simple building blocks via a linear sequence of six chemical reactions in five flow reactors. Sequential offline acidifications and filtrations afforded ciprofloxacin and ciprofloxacin hydrochloride. The overall yield of the eight-step sequence was 60 %. No separation of intermediates was required throughout the synthesis when a single acylation reaction was applied to remove the main byproduct, dimethylamine.

Visible Light Activation of Boronic Esters Enables Efficient Photoredox C(sp2 )-C(sp3 ) Cross-Couplings in Flow

We report herein a new method for the photoredox activation of boronic esters. Using these reagents, an efficient and high-throughput continuous flow process was developed to perform a dual iridium- and nickel-catalyzed C(sp2 )-C(sp3 ) coupling by circumventing solubility issues associated with potassium trifluoroborate salts. Formation of an adduct with a pyridine-derived Lewis base was found to be essential for the photoredox activation of the boronic esters. Based on these results we were able to develop a further simplified visible light mediated C(sp2 )-C(sp3 ) coupling method using boronic esters and cyano heteroarenes under flow conditions.

Use of a "Catalytic" Cosolvent, N,N-Dimethyl Octanamide, Allows the Flow Synthesis of Imatinib with no Solvent Switch

A general, efficient method for C-N cross-coupling has been developed using N,N-dimethyloctanamide as a catalytic cosolvent for biphasic continuous-flow applications. The described method was used to generate a variety of biarylamines and was integrated into a two-step sequence which converted phenols into biarylamines via either triflates or tosylates. Additionally, the method was applied to a three-step synthesis of imatinib, the API of Gleevec, in good yield without the need of solvent switches.

A Versatile Room-Temperature Route to Di- and Trisubstituted Allenes Using Flow-Generated Diazo Compounds

A copper-catalyzed coupling reaction between flow-generated unstabilized diazo compounds and terminal alkynes provides di- and trisubstituted allenes. This extremely mild and rapid transformation is highly tolerant of several functional groups.

Continuous-flow technology—a tool for the safe manufacturing of active pharmaceutical ingredients

In the past few years, continuous-flow reactors with channel dimensions in the micro- or millimeter region have found widespread application in organic synthesis. The characteristic properties of these reactors are their exceptionally fast heat and mass transfer. In microstructured devices of this type, virtually instantaneous mixing can be achieved for all but the fastest reactions. Similarly, the accumulation of heat, formation of hot spots, and dangers of thermal runaways can be prevented. As a result of the small reactor volumes, the overall safety of the process is significantly improved, even when harsh reaction conditions are used. Thus, microreactor technology offers a unique way to perform ultrafast, exothermic reactions, and allows the execution of reactions which proceed via highly unstable or even explosive intermediates. This Review discusses recent literature examples of continuous-flow organic synthesis where hazardous reactions or extreme process windows have been employed, with a focus on applications of relevance to the preparation of pharmaceuticals.