Comparative Studies of Cathodically-Promoted and Base-Catalyzed Michael Addition Reactions of Levoglucosenone

Abstract

Regioselective Michael addition of nitro and heterocyclic compounds to levoglucosenone, 1, is effectively catalyzed by amines and also by cathodic electrolysis. In comparison to the base-catalyzed reaction, it was found that under electrochemical conditions the reaction proceeds under milder conditions and with higher yields. Cathodically-initiated Michael addition of thiols to levoglucosenone using small currents produces the previously unknown threo addition product in several instances. The normal erythro isomer, identified as the kinetic product, tends to be formed when large currents are used. In contrast, slow, low current electrolyses promote equilibration of the two forms so that erythro can be converted to threo by the retro reaction and readdition. Addition of 2-naphthalenethiol to (R)-(+)-apoverbenone is also reported.

Bio‐available Solvent Cyrene: Synthesis, Derivatization, and Applications

“…It is unclear from theses tudies if Cyrenei sa na ctive substrate for the enzymes or if there are other problemsf or biocatalytic processes( see below). [59] As expected, Cyrene was also not ag ood solventf or the preparation of 2,4,5-trisubstituted-2-imidazolines 47 from the condensation reactiono fa ldehydes,s uch as 4-(trifluoromethyl)benzaldehyde (46), and ammonium carbonate (Scheme 12). [60] Instead of the desired product, ac omplex reaction mixture was obtained, which was presumably the result of the reactionoft he solvent with the reagents.…”

“…471 and 487) with aL D 50 > 2000 mg kg À1 (OECD No. [44] In related6 ,8-dioxabicyclo[3.2.1]octanone ring systemsi nw hich there is as ubstituent at the b-position, such as alcohol 24 [45] or pyrazole 25, [46] the ketal form can be isolated and characterized. [42] Althoughith as been given ah azard warning for being an eyei rritant (E319), Cyrene has received ECHA level 7c ertification.…”

“…[19] This is in contrast to at raditional ketone,s uch as acetone, that tend to exist predominantly in the ketone form in aqueouss olutions.T he equilibrium also can be shifted in the presence of 1,2-diols, which form cyclic acetals outo f the ketone moiety. [44] In related6 ,8-dioxabicyclo[3.2.1]octanone ring systemsi nw hich there is as ubstituent at the b-position, such as alcohol 24 [45] or pyrazole 25, [46] the ketal form can be isolated and characterized. An increased understandingo ft his equilibrium-specifically regarding the pH, temperature, and Scheme4.Nucleophilic additionst oC yrene (2).…”

Electrochemically Induced Addition Reactions in the Absence of Solvent and Supporting Electrolyte

“…[10,11] Actually, depending on the electrolysis procedure, the authors showed two different processes targeted at 2-nitro alcohols or 1,3-dinitro compounds. [12] We have now found that, under the conditions reported above, the direct electrolysis of pure nitromethane, under an inert atmosphere, could be conveniently used for a selective synthesis of the 2-nitro alcohols 6 by addition of an aldehyde 5 to the cathode compartment at the end of the electrolysis (Scheme 3).…”

Synthesis of amides from acid chlorides and amines in the bio-based solvent Cyrene™

“…A study into the hydration of Cyrene (1) was undertaken in order to better understand why it could be separated from the product amide via the addition of water. Whilst the hydrate of Cyrene 7 31 as well as related 6,8-dioxabicyclo[3.2.1]octanone ring systems in which there is a substituent at the -position are reported, 32,33 at the start of our study there is was no NMR data available for the hydrate or information on the effect of water concentration on the equilibrium. Very recently, De bryun et al reported on the hydration of Cyrene (1) and the ability of the solutions to solvate simple organic compounds.…”