Intramolecular Anodic Olefin Coupling Reactions:  The Use of Allylsilane Coupling Partners with Allylic Alkoxy Groups

Abstract

Intramolecular anodic olefin coupling reactions having an alkoxy substituent on the allylic carbon of an allylsilane moiety have been studied. These substrates were examined as part of an effort to determine the compatibility of the anodic olefin coupling reaction with the presence of very acid-sensitive functional groups and the construction of functionalized five-membered rings. In the initial experiment reported, an enol ether moiety was coupled to a trisubstituted allylsilane to afford a five-membered ring product without loss of the allylic alkoxy group. The reaction was stereoselective and could be used to generate a five-membered ring with three contiguous asymmetric centers. The stereochemical outcome of the reaction was best explained by a "pseudoequatorial" alkoxy group in the transition state; an argument that implied the reaction was under kinetic control. This suggestion was tested with the use of two electrolysis substrates that led to identical products through different transition states. The two substrates led to much different product ratios, proving that the reactions were not controlled by thermodynamics but rather governed by kinetic control. This observation was opposite to the conclusion reached with earlier vinylsilane-based substrates. Finally, the reactions were shown to be compatible with the presence of the alkoxy group even when challenged to form a fused bicyclic ring skeleton and a quaternary carbon. As in the initial case, the reaction to form a quaternary carbon was also highly stereoselective.

Synthetic Organic Electrochemistry: An Enabling and Innately Sustainable Method

“…Some of the most substantial advancements in electrochemical oxidative coupling reactions of the past 20 years have been developed by the Moeller − and Wright − groups. In this way, anodic oxidation has been shown to enable the coupling of two nucleophilic functional groups, thereby leading to new broadly useful umpolung disconnections.…”

Electrode Materials in Modern Organic Electrochemistry

“…Moeller also demonstrated that an ordered double layer can improve selectivity in an intramolecular cyclisation reaction by promoting cyclisation over solvent trapping (Figure 15 C). [193][194][195] Thea nodic oxidation and the ensuing cyclisation occur within the ordered environment of the double layer at the anode surface,w hich slows diffusion and excludes the methanol from the electrode surface that could otherwise interfere with cyclisation. Silyl protection of the internal alcohol moiety of the substrate was still necessary to prevent the intramolecular trapping by this competing nucleophile.…”

Electrochemical strategies for C–H functionalization and C–N bond formation

“…Here, atom-economical and regioselective platforms for direct functionalization of double or triple bonds allow access to a range of functionalized products, thereby offering considerable opportunities for strategic chemical synthesis. In addition to the intramolecular anodic olefin coupling reactions discussed in the previous section, other carbon- [849][850][851][852][853][854][855][856][857][858][859][860][861][862] as well as oxygen-based [863][864][865][866][867][868][869][870][871][872][873][874][875] nucleophiles have also been utilized in radical cation-initiated cyclization protocols for constructing C-C and C-O bonds, respectively. Furthermore, Moeller and coworkers have designed systems for direct functionalization of alkenes using nitrogen functionalities as trapping groups.…”