Highly Selective 1,2- and 1,4-Addition of Silyl Enol Ethers to alpha,beta-Unsaturated Carbonyl Compounds in 5 M Lithium Perchlorate-Nitromethane Medium

Entropic electrolytes for anodic cycloadditions of unactivated alkene nucleophiles

Unactivated alkenes were previously found to be effective carbon nucleophiles for anodic cycloadditions in lithium perchlorate/nitromethane electrolyte solution.

Construction of highly functionalized diazoacetoacetates via catalytic Mukaiyama-Michael reactions

Functionalized diazo acetoacetates are prepared by an efficient Mukaiyama-Michael reaction between methyl 3-(trialkylsilanoxy)-2-diazo-3-butenoate and alpha,beta-unsaturated enones. Vinyl ether and ketone derivatives are both accessible in good to excellent yield through this methodology. The mild Lewis acid zinc(II) triflate is the optimal catalyst, and its loading can be as low as 0.1 mol %. In addition, zinc triflate was also found to be a superior catalyst for the related Mukaiyama-aldol reaction.

Electrocatalytic Formal [2+2] Cycloaddition Reactions between Anodically Activated Enyloxy Benzene and Alkenes

Electrocatalytic formal [2+2] cycloadditions between anodically activated enyloxy benzene and alkenes have been accomplished in a lithium perchlorate/nitromethane electrolyte solution. The enyloxy benzene moiety of these electrolytic substrates played an important role in the formation of a radical cation that could accept nucleophilic alkenes, followed by intramolecular electron transfer between the cyclobutane and phenyl ether moieties of the intermediates.

Tandem addition beta-lithiation-alkylation sequence on alpha,beta-unsaturated aldehydes

A tandem reaction between (E)-cinnamaldehyde, 1a, and phenyllithium affording beta-substituted dihydrochalcones was recently reported. NMR spectroscopic studies on the reaction mixture, as well as isotopic exchange reactions and trapping of two intermediates, provide clues on the several mechanistic steps of this new reaction. Extended studies revealed that beta-alkyl-substituted alpha,beta-unsaturated aldehydes and aliphatic lithium reagents did not afford good yields of the tandem reaction products, while aromatic lithium reagents gave good results. The aggregation features of the aryllithium reagents and the extended charged delocalization effects are considered to promote beta-selectivity. This approach provides a convenient route for the synthesis of a wide variety of beta-alkyl-substituted dihydrochalcones.