Mild Base-Promoted Indole Annulation-Oxidative Cross- Coupling of 2-Nitrocinnamaldehydes with β-Tetralones for 3-Naphthylindole and 3-Naphthylbenzo[g ]indole Fluorophores

Ag(I)-catalyzed cyclization of o-alkynylacetophenones facilitated through acetal formation: synthesis of C3-naphthyl indole derivatives

A mild method for an efficient synthesis of C3-naphthyl indoles from o-alkynylacetophenones has been developed. This Ag-catalyzed transformation is assisted by the acetal formed under the reaction condition employing trimethyl orthoformate (TMOF). The role of acetal in promoting the reaction under ambient conditions has been established with control experiments. A range of C3-naphthyl indole derivatives have been synthesized in moderate to very good yields.

Annulation strategies for diverse heterocycles via the reductive transformation of 2-nitrostyrenes

Reduction of the stable nitro group is a fundamental and widely used transformation for the construction of complex and functionalized heterocyclic architectures. The unfolding of the reactivity of the nitro group in the 2-nitrostyrene moiety not only triggers the formation of carbon-nitrogen bonds, but also offers the opportunity for annulation and heteroannulation, thereby providing a cascade process for the synthesis of highly conjugated natural and unnatural molecules. In this review, we comprehensively discuss the use of 2-nitrostyrene motifs in the synthesis of various N-heterocycles. We offer readers an overview of the synthetic achievements achieved to date, highlighting their important features, reactivities, and mechanisms.

DDQ/FeCl3-mediated tandem oxidative carbon-carbon bond formation for the Synthesis of indole-fluorene hybrid molecules

A series of diverse and complex hybrid structures of indole bearing fluorene were obtained in the presence of DDQ with high regioselectivity under mild conditions from biaryl tethered 3-(methylene)indoline in good to excellent yields. The strategy involves tandem allylic Csp³-H oxidation and subsequent intramolecular carbon-carbon bond formation. The yield of the product was dramatically improved in the presence of additives such as FeCl₃ and molecular sieves (4 Å). A possible mechanism is proposed for this tandem process.

Base-promoted domino radical cyclization of 1,6-enynes

A good regioselective, high atom-economical and transition-metal-free method for the synthesis of α-functionalized ether derivatives via the domino radical cyclization of 1,6-enynes is described. A series of α-functionalized ether derivatives could be easily obtained in good yields with wide functional group tolerance by using less toxic and inexpensive Cs₂CO₃ as the base. The control experiment results show that the reaction involves a radical process. This strategy provides a regioselective way toward the formation of dual C-C bonds in one step.