Silica-supported 5-(pyrrolidin-2-yl)tetrazole: development of organocatalytic processes from batch to continuous-flow conditions

Bortolini, Olga; Caciolli, Lorenzo; Cavazzini, Alberto; Costa, Valentina; Greco, Roberto; Massi, Alessandro; Pasti, Luisa

doi:10.1039/c2gc16673a

Cited by 68 publications

(42 citation statements)

References 45 publications

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“…Seeberger and co‐workers developed an excellent homogeneous flow system with 5–10 mol % proline tetrazole‐catalyzed aldol and Mannich reactions in DMSO, and Luisi reported a homogeneous sustainable domino flow reaction with 12 mol % proline tetrazole in DMSO . In a heterogeneous flow system, Massi used prepared silica‐ or polymer‐supported proline tetrazole in a packed‐bed column with less polar solvents ,…”

Section: Methodsmentioning

confidence: 99%

Process Catalyst Mass Efficiency by Using Proline Tetrazole Column‐Flow System

Nakashima

Yamamoto

2018

Chemistry A European J

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Generally, organocatalysts are not decomposed during chemical transformation, which is different from traditional metal catalysts. To improve catalytic processes efficiency, various studies have been applied to flow synthesis for organocatalysis. Furthermore, many immobilized organocatalysts have been used for heterogeneous flow synthesis, which requires huge amounts of immobilized catalyst and requires several steps to prepare. We took advantage of organocatalysts with low-polarity organic solvent and developed a flow system through a packed-bed column with simply proline tetrazole (5-(2-pyrrolidinyl)-1H-tetrazole) for heterogeneous organocatalytic synthesis. Under ambient temperature, this heterogeneous organocatalyst continuous flow-column system with ketones as a donor provides aldol, Mannich, and o-nitroso aldol reactions in up to quantitative yields with excellent enantio- and chemoselectivity values. Our heterogeneous-flow synthesis provides extremely low process catalyst mass efficiency and continuous production without changing the packed-bed catalyst column.

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Section: Methodsmentioning

confidence: 99%

Process Catalyst Mass Efficiency by Using Proline Tetrazole Column‐Flow System

Nakashima

Yamamoto

2018

Chemistry A European J

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“…Temperatures were measured externally by an IR sensor. As described in [32], the system used for continuous-flow reactions was composed of an HPLC pump (Agilent 1100 micro series), an in-line pressure transducer, a thermostated microreactor holder (Peltier unit), a system to collect fractions and a data acquisition system (Agilent ChemStation). The units were connected by peek tubing (internal diameter 0.01 inch from Upchurch Scientific).…”

Section: Methodsmentioning

confidence: 99%

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

Zaghi¹,

Ragno²,

Carmine³

et al. 2016

Beilstein J. Org. Chem.

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A convenient heterogeneous continuous-flow procedure for the polarity reversal of aromatic α-diketones is presented. Propaedeutic batch experiments have been initially performed to select the optimal supported base capable to initiate the two electron-transfer process from the carbamoyl anion of the N,N-dimethylformamide (DMF) solvent to the α-diketone and generate the corresponding enediolate active species. After having identified the 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine on polystyrene (PS-BEMP) as the suitable base, packed-bed microreactors (pressure-resistant stainless-steel columns) have been fabricated and operated to accomplish the chemoselective synthesis of aroylated α-hydroxy ketones and 2-benzoyl-1,4-diones (benzoin- and Stetter-like products, respectively) with a good level of efficiency and with a long-term stability of the packing material (up to five days).

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“…30 Performing the reactions in toluene at 50°C in a packed-bed microreactor afforded the desired products 6 as a mixture of two diastereomers (2:1 to 3:1 anti to syn) with 68−82% ee for the anti diastereomer.…”

Section: Heterogeneous Reactionsmentioning

confidence: 99%

Asymmetric Organocatalysis in Continuous Flow: Opportunities for Impacting Industrial Catalysis

2015

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The review highlights the different advantages associated with organocatalytic transformations performed in continuous-flow systems and presents the reactions which have been successfully achieved to date. Particular focus is placed on the comparison between batch and flow applications in order to show the advantages and disadvantages and to demonstrate the great potential for applying organocatalysis as well as combined organo and photoredox catalyzed reactions in continuous flow.

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Silica-supported 5-(pyrrolidin-2-yl)tetrazole: development of organocatalytic processes from batch to continuous-flow conditions

Cited by 68 publications

References 45 publications

Process Catalyst Mass Efficiency by Using Proline Tetrazole Column‐Flow System

Process Catalyst Mass Efficiency by Using Proline Tetrazole Column‐Flow System

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

Asymmetric Organocatalysis in Continuous Flow: Opportunities for Impacting Industrial Catalysis

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