Seven‐Step Continuous Flow Synthesis of Linezolid Without Intermediate Purification

Multiphasic Continuous-Flow Reactors for Handling Gaseous Reagents in Organic Synthesis: Enhancing Efficiency and Safety in Chemical Processes

The use of reactive gaseous reagents for the production of active pharmaceutical ingredients (APIs) remains a scientific challenge due to safety and efficiency limitations. The implementation of continuous-flow reactors has resulted in rapid development of gas-handling technology because of several advantages such as increased interfacial area, improved mass- and heat transfer, and seamless scale-up. This technology enables shorter and more atom-economic synthesis routes for the production of pharmaceutical compounds. Herein, we provide an overview of literature from 2016 onwards in the development of gas-handling continuous-flow technology as well as the use of gases in functionalization of APIs.

Development of a Fully Continuous-Flow Approach Towards Asymmetric Total Synthesis of Tetrahydroprotoberberine Natural Alkaloids

Continuous flow synthetic technologies had been widely applied in the total synthesis in the past few decades. Fully continuous flow synthesis is still extremely focused on multi-step synthesis of complex natural pharmaceutical molecules. Thus, the development of fully continuous flow total synthesis of natural products is in demand but challenging. Herein, we demonstrated the first fully continuous flow approach towards asymmetric total synthesis of natural tetrahydroprotoberberine alkaloids, (-)-isocanadine, (-)-tetrahydropseudocoptisine, (-)-stylopine and (-)-nandinine. This method features a concise linear sequence involving four chemical transformations and three on-line work-up processing in an integrated flow platform, without any intermediate purification. The overall yield and enantioselectivity of this four-step continuous flow chemistry were up to 50 % and 92 %ee, respectively, in a total residence time of 32.5 min, corresponding to a throughput of 145 mg/h.

Total Synthesis of Glipizide and Glibenclamide in Continuous Flow

Glipizide and glibenclamide remain some of the widely prescribed antidiabetic sulfonylurea drugs for the treatment of type 2 diabetes mellitus. Herein the authors report on an isocyanate-free synthetic procedure towards the preparation of these on demand drugs at multigram scale using continuous flow technology. The safety concern over the use of isocyanates in most of the existing synthetic routes was dealt with in this present work by using N-carbamates synthesised in situ from activation of amines with chloroformates as safer alternatives. An overall yield of 80-85 % was obtained for the semi-telescoped steps within 10 min total residence time.

Continuous Flow Acylation of (Hetero)aryllithiums with Polyfunctional N,N-Dimethylamides and Tetramethylurea in Toluene

The continuous flow reaction of various aryl or heteroaryl bromides in toluene in the presence of THF (1.0 equiv) with sec -BuLi (1.1 equiv) provided at 25 °C within 40 sec the corresponding aryllithiums which were acylated with various functionalized N,N-dimethylamides including easily enolizable amides at -20 °C within 27 sec, producing highly functionalized ketones in 48-90% yield (36 examples). This method was well suited for the preparation of α-chiral ketones such as naproxene and ibuprofen derived ketones with 99% ee . A one-pot stepwise bis-addition of two different lithium organometallics to 1,1,3,3-tetramethyurea (TMU) provided unsymmetrical ketones in 69-79% yield (9 examples).

Sustainable Chemistry - An Interdisciplinary Matrix Approach

Within the framework of green chemistry, the continuous development of new and advanced tools for sustainable synthesis is essential. For this, multi-facetted underlying demands pose inherent challenges to individual chemical disciplines. As a solution, both interdisciplinary technology screening and research can enhance the possibility for groundbreaking innovation. To illustrate the stages from discovery to the implementing of combined technologies, a SusChem matrix model is proposed inspired by natural product biosynthesis. The model describes a multi-dimensional and dynamic exploratory space where necessary interaction is exclusively provided and guided by sustainable themes.