Formation of Fluorovinyl Spiro-[imidazole-indene] and α-Amino-β-naphthalenones via Rh(III)-Catalyzed Cascade C–H Functionalization

Abstract

An efficacious method for building fluorovinyl spiro-[imidazole-indene] and α-amino-β-naphthalenone skeletons synchronously has been shown to consist of Rh(III)-catalyzed C−H functionalization between 2H-imidazoles and difluoromethylene alkynes. This protocol demonstrates a practical and straightforward route for installing fluorine elements in the envisioned position of heterocyclic compounds.

Mechanistic insights into an NH4OAc-promoted imine dance in Rh-catalysed multicomponent double C–H annulations through an N-retention/exchange dual channel

“…Based on the above experiments, especially the isotopic experiments, ESI-MS analysis, and literature precedence, 13,14 a dual-channel mechanism is proposed (Fig. 2).…”

“…Readily available 4,5-diaryl 2 H -imidazole is an ideal cyclic DDG platform that may undergo doubly directed C–H annulations at the two aryls. Nonetheless, only two-component mono [4 + 2] 13 and [3 + 2] 14 annulations with alkynes/alkenes to obtain isoquinolines and spiroimidazole-indenes have been reported ( Scheme 1a ), and the mechanism of such transformations remains ambiguous. Dong assumed a direct process of Int-B→Int-C′ via reductive elimination (RE, Scheme 1b , path A), 13 a but the vital middle Int-C was not mentioned/identified.…”

Direct Assembly of Vinyl Fluorinated Isoquinolines Via Rh(III)-Catalyzed [4 + 2] Annulation

“…Coupled with their multifaceted reactivity, vinyl fluoride motifs have grabbed attention in medical fields . Therefore, fluorinated alkynes have widely emerged as an indispensable coupling partner for the construction of fluorinated heterocycles in C–H activation . For example, Loh and coworkers pioneered a [4 + 1] annulation of N -methoxyl arylamides for the formation of isoindoline-1-one derivatives, in which gem -difluoromethylene alkynes were used as a one-carbon donor.…”

Practical conversion of gem-difluorocyclopropenes for the chemodivergent assembly of fluorinated heterocyclic frameworks

“…4 More recently, a series of fluorinated π-compounds including perfluoroalkenes, gem -difluoroalkenes, gem -difluoromethylene alkynes, monofluoroalkynes and gem -difluoromethylene allenes have been developed to fulfil diverse C–H functionalization reactions, leading to combined heterocycle construction and fluorine incorporation in an efficient manner (Scheme 1a). 5,6 Despite the impressive advances, issues remain with the use and popularization of this protocol, e.g. the inevitable use of an expensive TM catalyst, the typically complex reaction conditions involving different additives/solvents/waste, and relatively limited reaction modes and fixed outcomes.…”