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.1. History of Continuous Processing in Other Industries Within the fine chemical and commodity chemical industries, continuous processing is a commonly used technique. The development of continuous processes in these industries is driven primarily

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Optimizing current chemical processes alone does not yield the improvements required in the fine chemical and pharmaceutical industries. At least partially, a switch from batch to continuous manufacturing is needed. Cost-, time-, and atom-efficient routes frequently demand the application of high temperatures, pressures, and concentrations, and/or the use of highly reactive reagents. These chemistries often cannot be employed in conventional reactors. Costly and long alternative synthetic routes are chosen instead. The application of continuous-flow microreactors allows to access “harsh” or “hazardous” reaction conditions and, furthermore, enables entirely new transformations.

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−1 region with respect to temperature In conclusion, a continuous process of dehydration, amorphization and recrystallization for the API of MCP H 2 O in the solid state was easily determined using a

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In order to measure heats of mixing or heats of dilution for many solutions by a continuous process accurately, a twin conduction type flow microcalorimeter has been constructed, improving the design of the same type of calorimeter reported previously. The thermal stability of the heat sink was enhanced by enlarged contact area of the main heat sink block with a thermostated water bath. Mixing efficiency of the mixing cell and the stability of the base line were improved by the use of a new mixing cell having a long mixing zone and symmetrically arranged sample and reference cells. Waiting time for establishment of thermal steady state was also reduced by sandwiching each of the cell by a pair of wide thermopiles plates and a pair of sub-blocks. Heats of dilution of aqueous urea solutions were measured by a continuous process, and results obtained well agreed with accepted values by Guckeret al. The accuracy and thermal resolution in this calorimeter were estimated to be less than 0.05% and 3 μJ·s−1.

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A safe and scalable procedure for the synthesis of 2-oxopropanethioamide, an intermediate in the synthesis of a potent β-secretase (BACE-1) inhibitor, from the reaction of acetyl cyanide with hydrogen sulfide gas under continuous-flow conditions has been developed. The toxic gas could be accurately dosed using a mass-flow controller or a peristaltic pump. The reaction proceeded smoothly at room temperature in the presence of a small amount of triethylamine as basic catalyst. After a residence time of 15 min, excellent yield (96%) and purity (>99%) were obtained for the target compound. The high reaction selectivity permitted a simple workup procedure consisting of evaporation of all volatiles.

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Journal of Flow Chemistry
Authors: Bernhard Gutmann, Paul Hanselmann, Michael Bersier, Dominique Roberge and C. Oliver Kappe

Herein, we present the development of a continuous-flow process for a difluoromethylation with difluorocarbene as the reactive reagent. The difluoromethylated product is a key intermediate during the synthesis of eflornithine, a pharmaceutical that is on the World Health Organization’s Model List of Essential Medicines. The developed procedure uses inexpensive and commercially available chlorodifluoromethane (CHF2Cl, Freon 22) as difluorocarbene source. Deprotonation of CHF2Cl with NaOH in a biphasic mixture of organic solvent-water generates the carbene. A fast subsequent reaction of the difluorocarbene with the substrate generates the desired product with excellent selectivity.

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Flow chemistry has attracted significant interest in pharmaceutical development, where substantial efforts have been directed toward the design of continuous processes. Here, we report a total synthesis of atropine in flow that features an unusual hydroxymethylation and separation of several byproducts with high structural similarity to atropine. Using a combination of careful pH control in three sequential liquid—liquid extractions and a functionalized resin, atropine is delivered by the flow system with >98% purity.

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Let {X n}n∈ℕ be a sequence of i.i.d. random variables in ℤd. Let S k = X 1 + … + X k and Y n(t) be the continuous process on [0, 1] for which Y n(k/n) = S k/n 1/2 for k = 1, … n and which is linearly interpolated elsewhere. The paper gives a generalization of results of ([2]) on the weak limit laws of Y n(t) conditioned to stay away from some small sets. In particular, it is shown that the diffusive limit of the random walk meander on ℤd: d ≧ 2 is the Brownian motion.

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The Sandmeyer reaction of anilines to generate aryl azides, followed by the Ru(porphyrin)CO-catalyzed addition to styrenes affording N-aryl aziridines was successfully performed for the first time in mesoreactors, under continuousflow conditions. Mesofluidic technology allowed for a rapid screening of different parameters and a quick identification of the optimized reaction conditions for the two separate steps. The two optimized reactions were then combined in a single continuous process that allowed a safe and efficient synthesis of N-arylaziridines from convenient commercially available starting materials.

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Hop pellets type 90 are the most frequent hop products used in brewing. They are usually manufactured by drying hop cones, temporary storage of dry and pressed cones, milling and pelletising. Other possibility is a complete integration of hop harvest, cone drying, milling and pelletising in continuous process without temporary storage of pressed cones. The paper deals with the losses of bitter substances (primary α-acids) during hop cones drying, their pelletisation by two manufacturing procedures and storage in different conditions. The results of this study show that integrated procedure of hop pelletising decreases the total loss of α-acids compared to the usual procedure. During storage of hop pellets (produced by integrated procedure) the highest decrease (loss) of α-acids content was observed in pellets stored at 21 °C in the presence of air and the lowest under inert atmosphere (N 2 ) at 4 to 7 °C, respectively.

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