Palladium Catalysis: One‐Pot Synthesis of Fluorenones

Abstract

Palladium-catalyzed one-pot synthesis of fluorenones from simple bromobenzaldehydes and arylboronic acids, is presented. The process involves the formation of dual C-C bond without isolating the initial Suzuki coupled product. Significantly, the strategy delivered the products in good to excellent yields and scale-up reaction is also feasible.

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

“…A more detailed investigation might be required to fully understand the mechanism of this oxidative benzylamine cyclization, however, a tentative mechanism is proposed in Scheme 8, based on our observations as well as mechanistic investigations detailed in previous reports concerning similar TBHP-promoted cyclizations of aromatic aldehydes [26,35]. Notably, the two major side products of this reaction (detected by TLC using authentic references) are the aldehyde 2l and, to a lesser extent, the carboxylic acid B, whereas formation of proposed intermediate aminofluorene 5 or other stable reaction intermediates was not observed.…”

“…Among these are radical cyclizations [22], Pschorr reactions [23], and diverse cycloaddition protocols [24,25]. Especially transitionmetal-catalyzed cross-coupling reactions starting from benzophenones, benzoic acids, dihalogenated benzene building blocks and others have emerged as new approaches in recent years [26][27][28]. Various approaches starting from functionalized biaryls have hereby attracted considerable interest, since the precursors are readily available by established cross-coupling reactions.…”

Recent Advances in Catalyzed Sequential Reactions and the Potential Use of Tetrapyrrolic Macrocycles as Catalysts

“…To exemplify the domino reaction (which can be extend to the cascade reaction), in 2018, Kumar and Satyanarayana [ 61 ] reported the obtainment of fluorenones, which have meaningful interest in the biomedical and material fields, from 2-bromobenzaldehyde ( Figure 7 , 1a) and phenylboronic acid ( Figure 7 , 2a), using palladium as a catalyst and tert -butyl hydroperoxide as an oxidant. Following the domino one-pot concept, after the catalyst’s action to form the Suzuki product ( Figure 7 , 3aa), the molecules undergo intramolecular transformations ( Figure 7 , steps A–C) to generate the desired product ( Figure 7 , 4aa), with 86% yield in the best condition studied.…”

“…Following the domino one-pot concept, after the catalyst’s action to form the Suzuki product ( Figure 7 , 3aa), the molecules undergo intramolecular transformations ( Figure 7 , steps A–C) to generate the desired product ( Figure 7 , 4aa), with 86% yield in the best condition studied. The authors also proposed the mechanism represented in Figure 7 [ 61 ].…”