One‐Pot Synthesis of 3‐(2‐Fluoroalkenyl)indoles

Abstract

An unprecedented one‐pot synthesis of 3‐(fluoroalkenyl)indoles was developed. This process involves a catalyst‐free Michael addition of β‐fluoro‐β‐nitrostyrenes to indoles in neat followed by elimination of HNO2 using DBU as a base. The effectiveness of this approach was demonstrated through the preparation of variety of target products in up to 75 % isolated yield.

Acid‐Mediated Three Component Assembly of 4‐Fluoropyrazoles from α‐Fluoronitroalkenes, Hydrazines, and Aldehydes

“…Here chemoselectivity of the reaction may be attributed to the high energy of C–F comparatively to the C–NO 2 bond. [17a] We believe that cycloaddition is the rate‐limiting step of the whole sequence since in most cases neither pyrazolidines 4 nor pyrazolines C were observed. However, oxidation step became more important for electron‐poor aldehydes (see Scheme ) as the presence of electron‐withdrawing group at the position 3 should increase the oxidation potential of pyrazolidine 4 .…”

“…Evidently, the key problem of such approaches is the availability of 1‐fluoroalkynes, that are described as unstable and explosive compounds . Recently we have demonstrated efficient synthesis and application of α‐fluorinated nitroalkenes as synthetic equivalents of fluoroalkynes in [3+2]‐cycloadditions towards monofluorinated pyrroles, NH‐ and 2,5‐disubstituted triazoles, indolizines and pyrazolo[1,5‐ a ]pyridines,, while Roy et al described the synthesis of 1,5‐disubstituted triazoles , . Preparation of 4‐fluoropyrazoles from nitroalkenes is highly attractive as a straightforward route to these type of pharmaceutically important heterocycles.…”

Diels‐Alder Reaction of β‐Fluoro‐β‐nitrostyrenes. Synthesis of Mono‐fluorinated Six‐Membered Derivatives

“…Starting β‐fluoro‐β‐nitrostyrenes were prepared according to the described procedures , . Nitrostyrenes 1a , 1c , 1d , 1e , 1f , 1h , 1k , 1m , 1n ; 1b , 1g ; 1i ; 1j are known compounds.…”

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

“…This process takes place with simultaneous elimination of bromine, and gives the target structures solely in the Z-isomeric form in high yields (up to 92%). These fluorinecontaining olefins activated by a nitro group proved to be the appealing building blocks for the construction of numerous monofluorinated compounds [51][52][53][54][55][56]. This paper is devoted to a new synthetic approach to novel monofluorinated bicyclic compounds, namely norbornenes and bicyclo[2.2.2]oct-2-enes and their subsequent functionalization.…”