Copper-Catalyzed Nucleophilic Cycloisomerization Cascade Constructing Azepinoindolizine.

Numerous effective bioisosteric replacements have been identified through substituting scaffolds and functional groups in lead molecules with alternative ones that preserve or enhance the desired biological activity of the original compound. Here, a copper-catalyzed nucleophilic cycloisomerization was developed to access potential bioisosteric replacements of azepinoindole. In this process, "tetra-alkene" characteristic of indolizine undergoes a 12π electrocyclization, offering a complementary method to obtain azepinoindolizine derivatives that are otherwise challenging to prepare through conventional means.

Divergent access to 5,6,7-perifused cycles.

Nitrogen-containing heterocycles are the key components in many pharmaceuticals and functional materials. In this study, we report a transition metal-catalyzed high-order reaction sequence for synthesizing a structurally unique N-center 5,6,7-perifused cycle (NCPC). The key characteristics include the formation of a seven-membered ring by the 8π electrocyclization of various alkenes and aromatic heterocycles as π-components, in which metal carbene species are generated that further induce the cleavage of the α-C-H or -C-C bond. Specifically, the latter can react with various nucleophilic reagents containing -O, -S, -N, and -C. The stereo-controlled late-stage modification of some complicated pharmaceuticals indicates the versatility of this protocol.

Cascade 8π Electrocyclization/Benzannulation to Access Highly Substituted Phenylpyridines.

A cascade 8π electrocyclization/benzannulation reaction was developed to obtain the synthetically important highly substituted phenyl-pyridines. This method shows great potential in the rapid and inexpensive application of the scalable and operationally simple production of accessible substrates. On the basis of the resulting phenyl-pyridine products, a new Ru catalyst and bidentate ligand were designed and prepared, further demonstrating its high practicability.

Divergent Synthesis of Highly Substituted Pyridines and Benzenes from Dienals, Alkynes, and Sulfonyl Azides.

Divergent synthesis is extremely important for the highly efficient preparation of structurally diverse target molecules. Herein, we describe a multicomponent cascade reaction, which allows access to highly substituted pyridines and benzenes by combining four individual steps in a one-pot manner from the same set of readily available starting materials. The azepine intermediates were first used as the precursors for 6π-electrocyclization to construct highly substituted pyridines and benzenes in a tunable manner.

Access to Benzylic Quaternary Carbons from Aromatic Ketones.

The construction of benzylic all-carbon quaternary stereocenters, which are ubiquitous in biomolecules and drugs, is a task of high practical significance. Herein, we disclose a highly efficient one-pot method of constructing all-carbon quaternary structural units from aryl ketones, revealing that the entire process involves three consecutive chemical events, namely nucleophilic addition, Meinwald 1,2-hydrogen migration, and alkylation. Interestingly, dimerization of acetophenones results in formation of 2,4-diarylfurans under the employed conditions rather than the quaternary carbon products.