Construction of N-Ferrocene Substituted Benzodihydrooxazoles via a Catalyst-Free Aza-Michael Addition/C(sp3)-O Bond Formation Tandem Reaction

A catalyst-free aza-Michael addition/C(sp³)-O bond formation tandem reaction of substituted amino ferrocenes with quinone esters was developed, which provided a green and efficient strategy for the construction of a C(sp³)-O bond from C(sp³)-H, and a series of N-ferrocene-substituted benzodihydrooxazoles were smoothly produced in moderate to excellent yields (up to >99% yield). The mechanism experiments showed that quinone esters performed as both substrate and oxidant. The salient features of this transformation include good functional group tolerance, broad substrate scope and mild conditions.

Palladium-Catalyzed Synthesis of Fused Carbo- and Heterocycles: Recent Advances

The use of palladium catalysts in fused ring synthesis has been increasingly noteworthy in recent years in organic synthesis. It has a lot of potential compared to other transition metal catalysts, because of its one-of-a-kind feature that makes them more widely applicable in a variety of disciplines application. Palladium is important in a variety of Heck processes, including intramolecular, intermolecular, and reductive Heck reactions, which produce diverse carbocycles and heterocycles of biological importance. Under optimal reaction conditions, carbocyclization or heterocyclization occurs, resulting in the production of numerous structural building blocks of naturally occurring compounds. Beside intramolecular Heck-type reactions, cycloaddition, cycloalkylation, oxidative coupling, C-H functionalization, cross-coupling reactions, and carboamidation reactions have also been employed extensively to access fused carbo- and heterocycles of immense biological importance. This review article provides a well-summarized discussion (since 2001) on fused carbo- and heterocycle ring synthesis using palladium catalysts, overviewing their applications, and mechanistic insights.

Pd-Catalyzed Regioselective Intramolecular Allylic C-H Amination of 1,1-Disubstituted Alkenyl Amines

Pd-Catalyzed intramolecular allylic C-H amination of 1,1-disubstituted alkenyl amines with various allylic tethers (X = O, NMs, CH₂) was developed. This process allows for the divergent synthesis of 1,3-X,N-heterocycles through a regioselective allylic C-H cleavage and π-allylpalladium formation. Particularly noteworthy is the use of substrates containing a labile allylic moiety and new simple catalytic systems capable of promoting highly chemo- and regioselective allylic C-H amination by overcoming significant challenges.