The benefits and limitations of a simple continuous flow setup for handling and performing of organolithium chemistry on the multigram scale is described. The developed metalation platform embodies a valuable complement to existing methodologies, as it combines the benefits of Flash Chemistry (chemical synthesis on a time scale of <1 s) with remarkable throughput (g/min) while mitigating the risk of blockages.

A simple and robust procedure for the synthesis and use of thermally unstable dichloromethyllithium in continuous flow mode is described. By utilizing residence times in the range of milliseconds for the generation and electrophilic quench of dichloromethyllithium, the straightforward synthesis of dichlorocarbinols and benzylic pinacol esters was realized at reaction temperatures of -30 °C, whereas typical temperatures in traditional batch mode are below -78 °C. The excellent purity profile obtained from the flow process allows us to directly telescope the exiting flow stream into semibatch quenches for further modifications. All transformations gave the desired products in remarkable purity and yield on gram scale with no need for chromatography.

A platform for conducting organolithium chemistry in continuous flow mode, covering the scales from medicinal chemistry to later phase process development, is described. The use of this flow setup, which mimics the concept of f lash chemistry on scale, has been demonstrated by the exemplary, large-scale preparation of (4-fluoro-2-(trifluoromethyl)phenyl)boronic acid following a reaction sequence of halogen/lithium exchange, borylation, and semibatch workup. Furthermore, the key factors and corresponding practical assessments required for the streamlined and seamless scale-up from lab environment to higher productivity are highlighted.

Taking the enkephalin synthesis on soluble polyethylene glycol support as a test case, this communication demonstrates the usefulness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to monitor each step of coupling as well as removal of the N-terminal protecting group of the polymer-bound growing peptide chain. With minute amounts of sample the high mass accuracy permits detection of side reactions as well as incomplete reaction products. #

The solid-phase synthesis of 4-(2-amino-6-phenylpyrimidin-4yl)benzamide, a compound obtained through combinatorial chemistry and parallel synthesis, can be scaled up directly on solid support in excellent yields and high purity. By applying highly loaded aminomethyl polystyrene as solid support, a good ratio between the product and the starting resin is achieved. For comparison, the synthesis was also performed in solution. The solid-phase synthesis approach has the advantage that the desired compound is easily and quickly accessible in sufficient quantities for early development demands.