Traceless Directing-Group Strategy in the Ru-Catalyzed, Formal [3 + 3] Annulation of Anilines with Allyl Alcohols: A One-Pot, Domino Approach for the Synthesis of Quinolines

Abstract

A unique, ruthenium-catalyzed, [3 + 3] annulation of anilines with allyl alcohols in the synthesis of substituted quinolines is reported. The method employs a traceless directing group strategy in the proximal C-H bond activation and represents a one-pot Domino synthesis of quinolines from anilines.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…Kapur and co-workers reported a similar sequence, but in absence of a second alcohol. 205 Hence, the etherification did not occur but elimination of water and further aromatisation to quinoline derivatives ( Scheme 26C ). More than 30 examples have been reported in this contribution.…”

A review on transition-metal mediated synthesis of quinolines

“…36 A domino approach has been developed by Gao et al (Scheme 8). 37 In this protocol benzimidoyl chlorides (51) undergoes reaction with 1,6-enynes (52) to form alkynyl amidine (53) which subsequently afford the desired quinolines motifs (54). The reaction proceeded through palladium catalyzed Sonogashira coupling to give good yield under mild reaction conditions utilizing easily accessible raw material.…”

“…In this reaction, a transient directing group strategy utilizing ruthenium-catalyzed C-H bond activation was used to deliver the required product. 53 A range of substituted quinolines (46) were synthesized using the palladium-catalyzed oxidative cyclization of aryl allyl alcohols (90) and anilines (35) by Xu and colleagues (Scheme 25). This process works well without the use of acid, base or any additive to deliver satisfactorily yield of products.…”

Copper‐Catalyzed Tandem Reaction of Enamino Esters with ortho‐Halogenated Aromatic Carbonyls: One‐Pot Approach to Functionalized Quinolines

“…Recently, Jiang's group developed an efficient method for the synthesis of functionalized quinolines by using a C–C double bond cleavage reaction (Scheme c) . In addition, the synthesis of quinolines by Ru‐catalyzed cyclization processes has also been reported by the Kapur, Sun, and Hu groups, respectively.…”