We report a new convenient and efficient method utilizing the tropylium ion as a mild and environmentally friendly organocatalyst to mediate retro-Claisen-type reactions.

Tropylium bromide undergoes noncatalyzed, regioselective additions to al arge variety of Michael acceptors.I n this way, acrylic esters are converted into b-bromo-a-cycloheptatrienylpropionic esters.T he reactions are interpreted as nucleophilic attacko fb romide ions at the electron-deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine-or phosphine-catalyzed Rauhut-Currier reactions.S ubsequent synthetic transformations of the bromo-cycloheptatrienylated adducts are reported.

Triflic acid efficiently promotes the reductive amination reactions of carbonyl compounds on a broad range of substrates.

The development of efficient methods for the metathesis and phosphorylation reactions of disulfide compounds is of widespread interest due to their important synthetic utility in polymer, biological, medicinal and agricultural chemistry. Herein, we demonstrate the use of N-heterocyclic carbenes (NHCs) as versatile organocatalysts to promote these challenging reactions under mild conditions. This metal- and oxidant-free protocol is operationally simple with very short reaction times. The interplay between the nucleophilicity and basicity of NHCs in these reactions were also elucidated by NMR studies and high-level ab initio calculations.

The Ritter reaction used to be one of the most powerful synthetic tools to functionalize alcohols and nitriles, providing valuable N-alkyl amide products. However, this reaction has not been frequently...