Diversity-oriented syntheses: coupling reactions between electron-deficient olefins and aryl aldehydes via C(sp2)-H functionalization

Diversity-Oriented Metal-Free Synthesis of Nitrogen-Containing Heterocycles Using Atropaldehyde Acetals as a Dual C3/C2-Synthon

A highly efficient and elegant diversity-oriented reaction paradigm employing atropaldehyde acetals as new dual C2/C3 synthons was developed under metal-free conditions using glycine esters as the counterpart reagents, which allowed rapid synthesis of two important nitrogen-containing heterocycles, pyrrolo[1,2-a]quinolines and 3,5-diarylpyridines. The divergent products are subtly controlled by the manipulation of the substitutional groups of glycine esters. When a N-arylglycine ester was used, pyrrolo[1,2-a]quinolines can be formed through cascade oxidative C-C cleavage/multiple cyclization. Instead, N-benzylglycine ester as the counter-reagent led to the synthesis of 3,5-diarylpyridines via two key C-N cleavages. Mild conditions, broad substrate scope, scalability and environmentally acceptable organic solvents rendered this method practical and attractive.

Synthesis of Dimeric Securinega Alkaloid Flueggeacosine B: From Pd-Catalyzed Cross-Coupling to Cu-Catalyzed Cross-Dehydrogenative Coupling

We completed the synthesis of dimeric high-oxidation-state securinega alkaloid flueggeacosine B via two synthetic routes from allosecurinine. The first-generation synthesis (seven overall steps) involved a Liebeskind-Srogl cross-coupling reaction for the union of two functionalized fragments, the organostannane and the thioester. As a means to further streamline the synthetic route, we have developed a visible-light-mediated Cu-catalyzed cross-dehydrogenative coupling (CDC) reaction between an aldehyde and an electron-deficient olefin. This enabled the second-generation synthesis of flueggeacosine B from allosecurinine in four overall steps. The newly developed CDC reaction paves a direct way to a conjugated dicarbonyl moiety, a ubiquitous structural moiety present in various natural products.

Recent advances in acyl radical enabled reactions between aldehydes and alkenes

Radical-mediated functionalization of alkenes has been emerging as an elegant and straightforward protocol to increase molecule complexity. Moreover, the abstraction of a hydrogen atom from aldehydes to afford acyl radicals has evolved as a rising star due to its high atom-economy and the ready availability of aldehydes. Considering the great influence and synthetic potential of acyl radical enabled reactions between aldehydes and alkenes, we provide a summary of the state of the art in this field with a specific emphasis on the working models and corresponding mechanisms. The discussion is divided according to the kind of alkenes and reaction type.

Heat- or light-induced acylarylation of unactivated alkenes towards 3-(α-acyl) indolines

A heat- or photoredox/iron dual catalysis-enabled rare example of radical acylation across unactivated alkenes with aldehydes.

Highly mono-selective ortho-methylthiolation of benzamides via cobalt-catalyzed sp2 C–H activation

A highly mono-selective ortho-methylthiolation of benzamides was achieved via Co-catalyzed coupling of benzamides with DMSO.

The radical acylarylation of N-arylacrylamides with aliphatic aldehydes using the photolysis of hypervalent iodine(iii) reagents

This article describes a variety of 3,3-disubstituted 2-oxindoles that bear carbonyl groups, which are efficiently obtained from a radical reaction between N-arylacrylamides and aliphatic aldehydes. The reaction is initiated by the photolysis of hypervalent iodine(iii) reagents and proceeds smoothly under mild, metal-free conditions.

Copper-catalyzed decarboxylative methylthiolation of aromatic carboxylate salts with DMSO

A novel copper-catalyzed decarboxylative methylthiolation of arenecarboxylate salts has been realized using DMSO as the methylthiolation source.

Copper-catalyzed alkylarylation of activated alkenes using isocyanides as the alkyl source: an efficient radical access to 3,3-dialkylated oxindoles

A novel copper-catalyzed oxidative cyclization of N-arylacrylamides for the synthesis of 3,3-dialkylated oxindoles is described using isocyanides as alkyl radical precursors.