Rh(III)‐Catalyzed Intramolecular Oxidative Annulation of Propargyl Amino Phenyl Benzamides to Access Pyrido/ Isoquinolino Quinoxalinones

Abstract

A rhodium catalyzed copper mediated double oxidative annulation of propargylamino phenyl benzamides is developed. A quick assembly of tri, tetra and penta cyclic pyrido/isoquinolo‐quinoxilines are thus achieved from readily available linear substrates. The reaction is shown to be very general by accommodating a large variety of substrates in the transformation. A mechanism through an amide directed C−H bond activation followed by an intramolecular alkyne activation/annulation followed by an oxidation is postulated.magnified image

Synthesis of Fused Tetracyclic Compounds via Oxidative Annulation: Access to Copper-Catalyzed Indolo[1,2-a]quinolines and to Ruthenium-Catalyzed Isoquinolin-1[2H]-ones

“…However, changing the conditions, isoquinolin-1(2H)-one 6a could be obtained using 2.2 equivalents of copper acetate monohydrate and dichloro(p-cymene)ruthenium(II) dimer as a catalyst, at the reflux of dichloroethane (DCE) for 16 h under air (Scheme 2c). 15 Some other conditions were tested to optimize the yields of 5a. Changing the solvent to toluene, DCE or tert-amyl alcohol did not improve the yields (Table 1, entries 2−4).…”

“…14 The group of Reddy also used a rhodium catalyst to successfully annulate propargyl amino phenyl benzamides to access isoquinolino quinoxalinones (Scheme 1b). 15 More recently, the group of Zhou reported an efficient copper-catalyzed preparation of benzo [3,4]indolo-[1,2-b]isoquinoline-8-ones (Scheme 1c). 16 In connection with our research interest focused on the use of organo bis-boranes as versatile intermediates in heterocyclic chemistry, 17 we herein report the synthesis of (en-3-yn-1yl)phenylbenzamides and their conversion to fused tetra-and pentacyclic compounds through intramolecular double oxidative annulation (Scheme 1d).…”

“…However, only a few examples of access to tetracyclic adducts have been described. − The group of Song developed a rhodium(III)-catalyzed intramolecular annulation triggered by C–H activation (Scheme a) . The group of Reddy also used a rhodium catalyst to successfully annulate propargyl amino phenyl benzamides to access isoquinolino quinoxalinones (Scheme b) . More recently, the group of Zhou reported an efficient copper-catalyzed preparation of benzo[3,4]indolo[1,2- b ]isoquinoline-8-ones (Scheme c) …”

“…In particular, alkynyl-tethered amides are well-recognized as versatile building blocks towards N -containing cyclic architectures and proved to be efficient in intramolecular oxidative annulations, leading to isoquinolinone fused tricyclic compounds . However, only a few examples of access to tetracyclic adducts have been described. − The group of Song developed a rhodium­(III)-catalyzed intramolecular annulation triggered by C–H activation (Scheme a) . The group of Reddy also used a rhodium catalyst to successfully annulate propargyl amino phenyl benzamides to access isoquinolino quinoxalinones (Scheme b) .…”

Rhodium-Catalyzed Annulation of Phenacyl Ammonium Salts with Propargylic Alcohols via a Sequential Dual C–H and a C–C Bond Activation: Modular Entry to Diverse Isochromenones

“…The chemistry that underpins dual C–H activations enabled by DG-based strategies has inspired us to design and execute various cascade reactions where the directing group plays a crucial role for efficient construction of polycyclic aromatics . We report herein an accidental discovery of three-point double annulation of propargylic alcohols with phenacyl amines through a dual C–H and C–C bond activation.…”