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The selective construction of medicinally and synthetically important indole-based unsymmetrical triarylmethanes using indoles and aldehydes is challenging because the significant nucleophilicity of indole leads to C-C coupling with an azafulvene intermediate to build up the alternative bis(indolyl)methane products, which may be useful synthons. A new, straightforward, ligand-free Cu catalytic strategy for easy syntheses of unsymmetrical indolotriarylmethanes and new bisindolylbenzoyl analogues is established through the dual C-C coupling of an assembly of three reaction partners comprising aldehydes, indoles, and arylboronic acids. More importantly, this approach is exploited for multifold C-C coupling cyclization reactions with C-C cleavage using symmetrical bisindolylbenzoylmethanes in the presence of an organic base and aerial molecular oxygen as a stoichiometric oxidant. In contrast to the formation of a simple cyclocondensation product indolocarbazole, it undergoes unprecedented selective pseudo-four-component tandem oxidative cyclization with fragmentation from a 1,3-dicarbonyl compound to produce valuable fused 5,7-dihydroindolo[2,3-b]carbazoles through the functionalization of two indole C(sp)-H and one C(sp)-H bond of the active methylene residue. For a better understanding of the new reactions, we have studied various competition experiments and ESI-MS and 3D Mid-IR-ATR spectral analyses of the ongoing reactions. The predicted DFT transition state model is also in agreement with the experimental results.

The versatile, one-pot synthesis of a series of alkyl aryl ketones is described using ethyl cyanoacetate as a new acylating agent.

Unprecedented I2-catalyzed α,α-C(sp3)-H, decarboxylative α-C(sp3)-H, lactonized α-C(sp3)-H, and α,β-C(sp3)-H functionalized 5- and 6-annulation as well as α-C(sp3)-H activated 6-lactonization of primary aliphatic amines are devised under aerobic conditions. The metal-free sustainable strategy was employed for the diverse construction of valuable five-and six-membered polycyclic N,O-heteroaromatics such as oxazoles, 1,4-oxazines, and oxazin-2-one with a rapid reaction rate and high yield. The viability of this mild nonmetallic catalysis is successfully verified through syntheses of labile chiral heterocyclic analogues. In contrast to the common practice, this method is not limited to use of prefunctionalized amines, directing groups (DGs) and/or transient DGs, metal catalysts, and traditional oxidants. The possible mechanistic pathway of the annulation reaction is investigated by control experiments and ESI-MS data collected for a reaction mixture of the ongoing reaction. The synthesized new compounds are potent organic nanobuilding blocks to achieve valuable organic nanomaterials of different sizes, shapes, and dimensions, which are under investigation for the discovery of high-tech devices of innovative organic nanoelectronics and photophysical properties.

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