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

Abstract

A series of diverse and complex hybrid structures of indole bearing fluorene were obtained in the presence of DDQ and FeCl3 with high regioselectivity under mild conditions from biaryl tethered 3-(methylene)indoline in good to excellent yields.

DDQ/Fe(NO3)3-Catalyzed Aerobic Synthesis of 3-Acyl Indoles and an In Silico Study for the Binding Affinity of N-Tosyl-3-acyl Indoles toward RdRp against SARS-CoV-2

“…However, based on our previous studies along with our present results of investigations, for the oxidation of the C-3 benzylidine indolines 2a , the generation of an allylic carbocation at the C-2 position in 2a followed by isomerization to produce the 3-indolyl carbocation is more facile compared to the direct formation of a diaryl carbocation at the C-3 position of indole in 2a′ due to aromatic stabilization. The energy of the intermediates was calculated through a density functional theory (DFT) study, and the reaction thermos-energy profile is shown in Figure .…”

“…Therefore, a mild and efficient method to access 3-acyl indoles is highly desired. With our continuous efforts after victorious developments of oxidative C–C/C–N bond-forming strategies, we envisaged that dehydrogenation at the α-sp 3 C–H bond of the arylsulfonamide moiety at the C-2 carbon in C-3-alkyl-/arylidine indolines could introduce oxidative hydroxylation or oxo-functionalization at the C-3 position via oxidative isomerization/aromatization to afford 3-acyl indoles. In this regard, a catalytic combination of DDQ and a nitrate source in the presence of molecular oxygen was anticipated as the most efficient oxidant .…”

Synthetic applications of hydride abstraction reactions by organic oxidants

“…Kar and co-workers demonstrated this (Scheme 25) in the conversion of indolene 121 to cationic indole derivative 122 . 80 An intramolecular Friedel–Crafts alkylation reaction provided fluorene-substituted indole 123 . Notably the isomeric substrate in which the indole nucleus is intact reacted far less efficiently, demonstrating the importance of starting material energy on oxidation rates.…”

DDQ as a versatile and easily recyclable oxidant: a systematic review

“…This pathway offers high functional group tolerance as shown in Scheme 19. 44 During oxidative C-C bond-forming reactions, the control of cyclization and polymer formation is quite tricky. DDQ has provided solution to these challenging problems by controlling the cyclization during C-C bond formation and suppressing the process of polymerization.…”