Continuous-flow Si-H functionalizations of hydrosilanes via sequential organolithium reactions catalyzed by potassium tert-butoxide

We herein report an atom-economic flow approach to the selective and sequential mono-, di-, and tri-functionalizations of unactivated hydrosilanes via serial organolithium reactions catalyzed by earth-abundant metal compounds. Based on the screening of various additives, we found that catalytic potassium tert-butoxide (t-BuOK) facilitates the rapid reaction of organolithiums with hydrosilanes. Using a flow microreactor system, various organolithiums bearing functional groups were efficiently generated in situ under mild conditions and consecutively reacted with hydrosilanes in the presence of t-BuOK within 1 min. We also successfully conducted the di-funtionalizations of dihydrosilane by sequential organolithium reactions, extending to a gram-scale-synthesis. Finally, the combinatorial functionalizations of trihydrosilane were achieved to give every conceivable combination of tetrasubstituted organosilane libraries based on a precise reaction control using an integrated one-flow system.11Nsciescopu

Direct Aryl‐Aryl Coupling without Pre‐Functionalization Enabled by Excessive Oxidation of Two‐Electron Ag(I)/Ag(III) Catalyst

Reported herein is a catalytic platform for formation of unsymmetrical biaryls by the coupling between inert Csp2−CH3 and Csp2−H via a tandem catalytic strategy. The platform utilizes traditional AgNO3 catalyst and excess amount of K2S2O8 oxidant. The excessive oxidant present converts the traditional one‐electron Ag(I)/Ag(II) chemistry to two‐electron Ag(I)/Ag(III) one, enabling one‐pot synthesis of aryl‐aryl scaffolds by using unactivated cheap commodity chemicals.111Nsciescopu

A numbering-up metal microreactor for the high-throughput production of a commercial drug by copper catalysis

Microreactors are emerging as an efficient, sustainable synthetic tool compared to conventional batch reactors. Here, we present a new numbering-up metal microreactor by integrating a flow distributor and a copper catalytic module for high productivity of a commercial synthetic drug. A flow distributor and an embedded baffle disc were manufactured by CNC machining and 3D printing of stainless steel (S/S), respectively, whereas a catalytic reaction module was composed of 25 copper coiled capillaries configured in parallel. Eventually, the numbering-up microreactor system assembled with functional modules showed uniform flow distribution and high mixing efficiency regardless of clogging, and achieved high-throughput synthesis of the drug "rufinamide", an anticonvulsant medicine, via a Cu(i)-catalyzed azide-alkyne cycloaddition reaction under optimized conditions.11Nsciescopu

Scalable Subsecond Synthesis of Drug Scaffolds via Aryllithium Intermediates by Numbered-up 3D-Printed Metal Microreactors

© Continuous-flow microreactors enable ultrafast chemistry; however, their small capacity restricts industrial-level productivity of pharmaceutical compounds. In this work, scale-up subsecond synthesis of drug scaffolds was achieved via a 16 numbered-up printed metal microreactor (16N-PMR) assembly to render high productivity up to 20 g for 10 min operation. Initially, ultrafast synthetic chemistry of unstable lithiated intermediates in the halogen-lithium exchange reactions of three aryl halides and subsequent reactions with diverse electrophiles were carried out using a single microreactor (SMR). Larger production of the ultrafast synthesis was achieved by devising a monolithic module of 4 numbered-up 3D-printed metal microreactor (4N-PMR) that was integrated by laminating four SMRs and four bifurcation flow distributors in a compact manner. Eventually, the 16N-PMR system for the scalable subsecond synthesis of three drug scaffolds was assembled by stacking four monolithic modules of 4N-PMRs.11Nsciescopu

Exploring ultrafast flow chemistry by autonomous self-optimizing platform

The rapid development of novel synthetic routes for pharmaceutical compounds is highly attractive for overcoming pandemic and epidemic-prone diseases like COVID-19. Herein, we report an automated microreactor platform (AMP) with Bayesian optimization (BO) that can autonomously explore the optimal conditions for ultrafast synthesis of biologically active thioquinazolinone. First, AMP operation is successfully demonstrated with full control of quantitative variables, specifically reaction volume, temperature, and flow rate, allowing to sequentially conduct a total of 80 experiments planned by the user. Next, BO enables the AMP to autonomously self-optimize the reaction conditions, demonstrating the high efficiency of the fully automated AMP. The fully automated approach is extended to optimize more complex variables including a categorical variable (i.e. the type of organolithium for synthesis), revealing that phenyllithium (PhLi) gives superior yield for synthesizing thioquinazolinone. In addition, the autonomous AMP is utilized for combinatorial chemistry to sequentially synthesize a library composed of nine types of S-benzylic thioquinazolinone under autonomously optimized conditions within only 20 min