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Regio- and Stereoselective Electrochemical Alkylation of Morita-Baylis-Hillman Adducts

Giulio Bertuzzi*, Giada Ombrosi and Marco Bandini*

*Center for Chemical Catalysis -C3-, Alma Mater Studiotum - UniversitÓ di Bologna, Via Selmi 2, 40126 Bologna, Italy, Email: giulio.bertuzzi2unibo.it, marco.bandiniunibo.it

G. Bertuzzi, G. Ombrosi, M. Bandini, Org. Lett., 2022, 24, 4354-4359.

DOI: 10.1021/acs.orglett.2c01529


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Abstract

Exposure of N-acyloxyphthalimides (redox-active esters) to galvanostatic electroreductive conditions enables a general regio- and stereoselective alkylation of Morita-Baylis-Hillman compounds in high yields. The method offers wide functional group tolerance.


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proposed mechanism



Optimized general procedure for the eChem alkylation of MBH adducts

The ElectraSyn vial (5 mL), equipped with a stir bar, was charged with MBH acetate (0.15 mmol), redox-active ester (0.30 mmol) and TEABF4 (65.1 mg, 0.30 mmol). The ElectraSyn vial cap, equipped with anode (Zn) and cathode (graphite) was inserted into the mixture and closed with a rubber septum. The vessel was evacuated and backfilled with N2 three times, then dry DMF (3 mL) was added, and the solution bubbled with N2 (balloon) under stirring for 1 min. The reaction mixture was electrolyzed (under N2, balloon) at a constant current of 2 mA, until a total charge of 0.60 F (4 F/mol) was reached (ca. 8 h). The ElectraSyn vial cap was removed, and the electrodes and vial were rinsed with EtOAc (10 mL) and HCl(aq) (1M, 10 mL), which were combined with the crude mixture in a separatory funnel. Then, the organic layer was separated, the aqueous layer was extracted with EtOAc (2 x 10 mL) and the combined organic layers were washed with HCl(aq) (0.1 M, 3 x 10 mL), dried over Na2SO4 and concentrated in vacuo. The crude product was finally purified by flash chromatography (nHex/Et2O mixtures).


Key Words

elimination, allylation


ID: J54-Y2022