Approaches for Performing Reductions under Continuous-Flow Conditions

Abstract

A concise overview of approaches to perform reductions of various functionalities including aldehydes, ketones, esters, imines, ­nitriles, nitro groups, alkenes and alkynes under continuous-flow conditions are highlighted and discussed in this short review.1 Introduction2 Reduction of Aldehydes, Ketones and Esters3 Reduction of Imines and Nitriles4 Reduction of Nitro Groups5 Reduction of Alkenes6 Partial Reduction of Alkynes7 Conclusion

C-N Bond Formation by Consecutive Continuous-Flow Reductions towards A Medicinally Relevant Piperazine Derivative

“…In the continuous-flow synthesis of aldehydes from esters, the use of diisobutylaluminum hydride (DIBAL-H) has been widely reported [ 34 , 35 , 36 , 37 ], besides other related reducing agents, such as diisobutyl- tert -butoxyaluminum hydride (LDBBA) [ 38 ]. Reductive aminations also proved their utility in flow chemistry [ 39 ], especially when catalytic hydrogenation is used, which is well-suited to continuous transformations, since it is typically free from side-products, and the removal of excess hydrogen is fairly simple [ 40 , 41 ]. The application of reductive amination in continuous-flow hydrogenation equipment for API production has been reported in the literature [ 22 , 42 ].…”

Continuous flow asymmetric synthesis of chiral active pharmaceutical ingredients and their advanced intermediates

“…Continuous flow reactors have emerged as a useful platform for the efficient, safe and scalable utilization of gases in chemical synthesis. 61 Although asymmetric hydrogenations have successfully been applied for the synthesis of chiral pharmaceuticals under continuous flow conditions, 38 the application of further gas–liquid transformations for asymmetric flow API synthesis is scarcely exemplified. In fact, we found only one contribution.…”

“… 37 Also, asymmetric hydrogenations are excluded from the scope of the present study due to the availability of specialized recent reviews on that topic. 38 In the following three sections, contributions on continuous flow asymmetric synthesis of chiral APIs and their advanced intermediates are categorized on the basis of the nature of chiral catalysis employed in the key synthetic steps to introduce asymmetry.…”

An Easy Approach to Obtain Alcohol-Amines by Reduction of Alcohol Functionalized Imines

“…The reduction of imines to isolate amines is a well-known field of study. In fact, it is one of the central reactions in organic chemistry, and the search for more efficient and practical synthetic methods for carrying out this reduction is a theme of constant interest [3][4][5]. Many reduction agents have been tested in order to produce the mentioned transformation, and H2 [6], silanes [7,8], boranes [9], and borohydrides [10] are maybe the most popular ones.…”