@article { ISI:000332784900001, title = {Continuous flow nitration in miniaturized devices}, journal = {Beilstein Journal of Organic Chemistry}, volume = {10}, year = {2014}, month = {FEB}, pages = {405-424}, publisher = {BEILSTEIN-INSTITUT}, type = {Review}, address = {TRAKEHNER STRASSE 7-9, FRANKFURT AM MAIN, 60487, GERMANY}, abstract = {

This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed.

}, keywords = {continuous flow, flow chemistry, microreactors, nitration, nitric acid, Tubular reactor}, issn = {1860-5397}, doi = {10.3762/bjoc.10.38}, author = {Kulkarni, Amol A.} } @article { ISI:000346134300012, title = {Continuous-flow meerwein arylation}, journal = {Journal of Flow Chemistry}, volume = {4}, number = {4}, year = {2014}, month = {DEC}, pages = {211-216}, publisher = {AKADEMIAI KIADO RT}, type = {Article}, address = {PRIELLE K U 19, PO BOX 245,, H-1117 BUDAPEST, HUNGARY}, abstract = {

The continuous-flow Meerwein arylation is demonstrated for a set of few aryl donors (anilines and m-aminoacetophenone) and specific radical acceptors. Homogeneous catalyst (CuBr in HBr and CuCl in HCl) was used to facilitate the reaction. The effect of parameters, viz., temperature, catalyst concentration, residence time, and concentration of the radical acceptor on the yield of the arylated product, was studied. The yield of the aryl derivative obtained by continuous-flow syntheses was always better than the respective experiments in batch mode. Flow synthesis allows easy variation in these parameters and thus allows going close to the maximum possible yields in a system where the relative rates of different reactions create a complex situation. Temperature plays a crucial role by affecting the rates as well as by governing the system homogeneity. The nitrogen bubbles generated in the reaction helped to avoid any channel blockage.

}, keywords = {diazonium salt, flow chemistry, homogeneous catalyst, Meerwein arylation, micromixer, multistep synthesis}, issn = {2062-249X}, doi = {10.1556/JFC-D-14-00023}, author = {Bhaya, Vinay G. and Joshi, Ramesh A. and Kulkarni, Amol A.} } @article {46958, title = {Organocatalytic cascade knoevenagel-michael addition reactions: direct synthesis of polysubstituted 2-amino-4H-chromene derivatives}, journal = {Catalysis Letters}, volume = {150}, year = {2020}, month = {AUG}, pages = {2331-2351}, type = {Article}, abstract = {

In this report, we documented novel strategy for the synthesis of bioactive polysubstituted 2-amino-4H-chromine derivatives under a heterogeneous Al-MCM-41-LDH@APTES (ALAM) catalysis. A synthetic procedure is developed to prepare Al-MCM-41-LDH@APTES (ALAM) heterogeneous basic catalysts. Mesoporous Al-MCM-41 is functionalized by known grafting chemistry via layered double hydroxide (LDH) nanosheets and (3-aminopropyl)triethoxysilane (APTES) moiety as a basic organocatalyst. The resulting catalysts contain amino group functionality on the external surface as well as inside the layers and the basicity can be tuned by the loading of APTES. The samples were fully characterized by Si-29 and C-13 CP/MAS NMR, infrared absorption spectroscopy, TEM, XPS, EDX, TGA, XRD, CO2-TPD, N-2 adsorption isotherms measurements, and they were successfully examined for the cascade type Knoevenagel-Michael addition reactions. The product yields associated with these substrates were optimized, and key reaction parameters affecting the yields were identified. The present catalytic method is simple and robust for diversity oriented synthesis which proceeds good to excellent yields without generating any hazards waste. The broad substrate scope, excellent functional group compatibility makes this protocol highly useful towards synthesis of polysubstituted alpha-cyanoacrylates, alpha-cyanoacrylonitriles and 2-amino-4H-chromenes with an electron-donating or electron-withdrawing group. We have also successfully established a flow reaction system, gram-scale synthesis as well as catalyst recyclability up to six catalytic cycles without appreciable loss of its activity. Graphic

}, keywords = {2-Amino-4H-chromines, Amine functionalized solid catalysts, cascade synthesis, Diversity oriented syntheses (DOS), flow chemistry}, issn = {1011-372X}, doi = {10.1007/s10562-019-03089-8, Early Access Date = FEB 2020}, author = {Jadhav, Sanjay N. and Patil, Seema P. and Sahoo, Dipti Prava and Rath, Dharitri and Parida, Kulamani and Rode, Chandrashekhar V.} } @article {49512, title = {Continuous flow telescopic synthesis of 3-methoxy propiophenone by the grignard reaction}, journal = {Organic Process Research \& Development}, volume = {29}, year = {2025}, month = {JAN}, pages = {450-459}, type = {Article}, abstract = {

The synthesis of 3-methoxypropiophenone 1, a crucial intermediate in the production of the analgesic tapentadol hydrochloride, was investigated using a multistep continuous flow process. The approach is based on the Grignard reaction. A series of continuously stirred tank reactors (CSTRs) were employed: the first reactors facilitated the continuous generation of Grignard reagents 3, which then reacted with propionitrile in the next CSTR to yield 1. This was followed by quenching, neutralization, and phase separation, conducted under varying temperatures and residence times. When compared to a 50\% yield from an optimized batch synthesis protocol, a continuous flow synthesis helped achieve an 84\% yield of the desired product in a much shorter reaction time. A kinetic model was developed to predict the Grignard reagent formation and product yield, revealing that the mass transfer effect is insignificant at a higher stirring rate. The approach is highly scalable for the synthesis of pharmaceutical intermediates.

}, keywords = {batch and continuous reaction, flow chemistry, Grignard reaction, heterogeneous kinetics}, issn = {1083-6160}, doi = {10.1021/acs.oprd.4c00447}, author = {Wankhede, Pranali and Kulkarni, Amol A.} }