English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Reactivity towards p-methoxybenzaldehyde (ArCHO) of electrochemically generated phosphonate carbanions has been investigated. Electrolyses were carried out at a mercury cathode in DMF and two routes to the desired carbanion have been compared: (i) Deprotonation of phosphonates of general formula (EtO) 2 P(O)CHYW (Y = W = Cl; Y = H, W = Cl; Y = Cl, W = CO 2 Et; Y = H, W = CO 2 Et; Y = CH 3 , W = CO 2 Et; Y = Cl, W = CH 3 ), by the bases resulting from the electroreduction of azobenzene; addition of the carbanion formed onto the carbonyl group takes place and leads to the adduct (EtO) 2 P(O)CYW(Ar)O − . (ii) Two-electron reduction of halophosphonates (EtO) 2 P(O)CXYW (X = Cl, Y and W as above; X = Br, W = CO 2 Et, Y = Cl, Br, or CH 3 ); when no H atom is present on the carbon bearing the phosphonate group (Y and W ≠ H), the same evolution leading to the above adduct is observed; on the contrary, when Y = H, the electrogenerated carbanion deprotonates the substrate and the resulting carbanion [Formula: see text] reacts with the aldehyde, giving the adduct(EtO) 2 P(O)CXW(Ar)O − .Evolution of the intermediate adduct depends on the substituants Y (or X) and W: when W = CO 2 Et, whatever the nature of Y (or X), diethyl phosphate is eliminated with formation of the ethylenic ArCH = CWY (or X) (Wittig–Horner reaction); the same evolution is observed when Y = W = Cl. When W = Cl and Y = H or CH 3 , the final product is the phosphonate epoxyde resulting from chloride elimination (Darzens reaction).Chemo- and stereoselectivity depend only on the nature of Y and W but are independent of the mode of generation of the carbanion. Yields are limited by side-protonation reactions, which are related to the basicity of the phosphonate carbanions. Analysis of the results permits selection of the optimal electrolysis conditions for purposes of synthesis. Keywords: electrosynthesis, electrogenerated bases, phosphonates, Wittig–Horner.

Carbanions phosphonate préparés par voie électrochimique: formation et réactivité vis-à-vis d'un aldéhyde