Investigation of a Lithium-Halogen Exchange Flow Process for the Preparation of Boronates by Using a Cryo-Flow Reactor

A Synthetic Approach to Dimetalated Arenes Using Flow Microreactors and the Switchable Application to Chemoselective Cross-Coupling Reactions

In spite of their potential utility, the chemistry of dimetalated arenes is still in its infancy because they are extremely difficult to synthesize. We report a novel method of synthesizing arenes bearing a boryl group and a metallic substituent, such as boryl, silyl, stannyl, or zincyl groups, in an integrated flow microreactor based on the generation and reactions of aryllithiums bearing a trialkyl borate moiety. The bimetallic arenes showed a remarkable chemoselectivity in palladium-catalyzed cross-coupling reactions. The selectivity was switched by the selection of the metal species that constitutes the dimetalated arenes as well as appropriate catalysts.

Generation and Reaction of Functional Alkyllithiums by Using Microreactors and Their Application to Heterotelechelic Polymer Synthesis

Flow microreactors enabled the successful generation of various functional alkyllithiums containing electrophilic functional groups, as well as the use of these alkyllithiums in subsequent reactions. The high reactivity of these series of reactions could be achieved by the extremely accurate and selective control of residence time. Moreover, integrated flow microreactor systems could be used to successfully synthesize heterotelechelic polymers with two functionalities, one at each end, via a process involving controlled anionic polymerization initiated by functional alkyllithium compounds, followed by trapping reactions with difunctional electrophiles.

Visible-Light Photocatalytic Difluoroalkylation-Induced 1, 2-Heteroarene Migration of Allylic Alcohols in Batch and Flow

A convenient method for the preparation of sp³-rich heterocycles is reported. The method comprises a photocatalytic difluoroalkylation-induced 1,2-heteroarene migration of allylic alcohols. Here we describe for the first time the benefits of using flow to facilitate such migration reactions, including shorter reaction times, higher selectivities, and opportunities to scale the chemistry.

Sodiation of Arenes and Heteroarenes in Continuous Flow

The first sodiations of (hetero)arenes in continuous flow using NaDA (sodium diisopropylamide) in Me₂ EtN are reported. This flow procedure enables sodiation of functionalized arenes and heteroarenes that decompose under batch-sodiation conditions. The resulting sodiated (hetero)arenes react instantly with various electrophiles, such as ketones, aldehydes, isocyanates, alkyl bromides, and disulfides, affording polyfunctionalized (hetero)arenes in high yields. Scale-up is possible without further optimization.

Taming hazardous chemistry by continuous flow technology

Over the last two decades, flow technologies have become increasingly popular in the field of organic chemistry, offering solutions for engineering and/or chemical problems. Flow reactors enhance the mass and heat transfer, resulting in rapid reaction mixing, and enable a precise control over the reaction parameters, increasing the overall process selectivity, efficiency and safety. These features allow chemists to tackle unexploited challenges in their work, with the ultimate objective making chemistry more accessible for laboratory and industrial applications, avoiding the need to store and handle toxic, reactive and explosive reagents. This review covers some of the latest and most relevant developments in the field of continuous flow chemistry with the focus on hazardous reactions.

Hydrolysis of 8-(pinacolboranyl)quinoline: where is the 8-quinolylboronic acid?

The compound 8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-quinoline was prepared and found to hydrolyze rapidly in air; however, the expected product (quinolin-8-yl)boronic acid was not observed. Instead, the (quinolinium-8-yl)trihydroxyborate zwitterion or an anhydride were observed depending on the conditions of hydrolysis. The two products are related to one another in the degree of hydration, and the two forms could be interconverted. Both hydrolysis products were structurally characterized. Additionally, a commercial sample of ‘8-quinolylboronic acid’ was actually found to be the anhydride. The results call into question whether monomeric (quinolin-8-yl)boronic acid can actually be isolated in the neutral Lewis base-free form.

Development of a web-based platform for studying lithiation reactions in silico

A novel integrated web-based system has been developed to rationalise and predict lithiation reactions in silico.

A practical deca-gram scale ring expansion of (R)-(−)-carvone to (R)-(+)-3-methyl-6-isopropenyl-cyclohept-3-enone-1

A route to enantiopure (R)-(+)-3-methyl-6-isopropenyl-cyclohept-3-enone-1, an intermediate for terpenoids, has been developed and includes a highly chemo- and regioselective Tiffeneau–Demjanov reaction.

Continuous flow magnesiation of functionalized heterocycles and acrylates with TMPMgCl⋅LiCl

A flow procedure for the metalation of functionalized heterocycles (pyridines, pyrimidines, thiophenes, and thiazoles) and various acrylates using the strong, non-nucleophilic base TMPMgCl⋅LiCl is reported. The flow conditions allow the magnesiations to be performed under more convenient conditions than the comparable batch reactions, which often require cryogenic temperatures and long reaction times. Moreover, the flow reactions are directly scalable without further optimization. Metalation under flow conditions also allows magnesiations that did not produce the desired products under batch conditions, such as the magnesiation of sensitive acrylic derivatives. The magnesiated species are subsequently quenched with various electrophiles, thereby introducing a broad range of functionalities.