Synthesis of Azaheterocycles from Aryl Ketone O-Acetyl Oximes and Internal Alkynes by Cu–Rh Bimetallic Relay Catalysts

Abstract

A synthetic method for azaheterocycles from aryl ketone O-acetyl oximes and internal alkynes has been developed by using the Cu(OAc)(2)-[Cp*RhCl(2)](2) bimetallic catalytic system. The reactions proceeded with both of anti- and syn-isomers of oximes with a wide scope of substituents. The Cu-Rh bimetallic system could be applied for the synthesis of isoquinolines as well as β-carboline, furo[2.3-c]pyridine, pyrrolo[2,3-c]pyridine, and thieno[2,3-c]pyridine derivatives.

Highly efficient and stable peracid for rapid and selective oxidation of aliphatic amines to oximes

“…It was also observed that, oxime selectivity increases with temperature. As we increased temperature from room temperature (30 °C) to 50 °C oxime selectivity was also increased from 53% to 90% (Table 2 entries [10][11][12]. Further rise in the temperature does not show any influence on the oxime selectivity ( Table 2, entry 13).…”

Versatile Synthesis of Benzothiophenes and Benzoselenophenes by Rapid Assembly of Arylzinc Reagents, Alkynes, and Elemental Chalcogens

“…First, condensation of benzothiophene-6-carbaldehyde 3 ha with p-anisidine was followed by rhodium(III)-catalyzed, aldimine-directed oxidative annulation with diphenylacetylene [20] to afford, upon hydrolysis, 7H-indeno [5,6-b]thiophen-7-one 8 (Scheme 7 a). Second, O-acetyloxime 9 derived from 6-acetylbenzothiophene 3 ia was subjected to rhodium(III)catalyzed redox-neutral annulation with diphenylacetylene [21] to afford thieno[3,2-g]isoquinoline 10 (Scheme 7 b). Finally, imine 11 derived from 6-aminobenzothiophene 3 oa and acetophenone participated in a palladium-catalyzed dehydrogenative cyclization reaction [22] to afford 7H-thieno[3,2f]indole 12.…”

Rhodium‐Catalysed [4+2] Annulation of Aromatic Oximes with Terminal Alkenes by C−H/N−O Functionalization towards 3,4‐Dihydroisoquinolines

“…[2,3] Despite substantial progress in the field, the development of highly atom-economic, sustainable routes that can achieve CÀ H functionalization under external-oxidizing-reagent-free conditions that release nontoxic waste products (e. g., H 2 O) remains a challenging area. [3][4][5][6] While the annulation of aromatic oximes with internal alkynes has been thoroughly investigated for the preparation of 3,4-disubstituted isoquinolines (Scheme 1a-i), [3,5] similar versions with alkenes are rare. [3][4][5][6] While the annulation of aromatic oximes with internal alkynes has been thoroughly investigated for the preparation of 3,4-disubstituted isoquinolines (Scheme 1a-i), [3,5] similar versions with alkenes are rare.…”

“…[4] In recent years, transition-metalcatalysed intermolecular annulation of aromatic oximes and their derivatives (often esters) with unsaturated hydrocarbons (e. g., alkynes, allenes, alkenes, ketenes) have proved to be promising platforms for the preparation of nitrogen-containing heterocycles, wherein the N À O bond in aromatic oximes serves as the internal oxidative chelation group to selectively achieve ortho-C(sp 2 )À H functionalization. [3][4][5][6] While the annulation of aromatic oximes with internal alkynes has been thoroughly investigated for the preparation of 3,4-disubstituted isoquinolines (Scheme 1a-i), [3,5] similar versions with alkenes are rare. [6] Moreover, these transformations focus on special alkenes, including vinyl acetates, [6a] 1,3-dienes [6b] and electron-poor alkenes, [6c] which serve as convenient acetylene equivalents for the synthesis of 3-substituted isoquinolines.…”

“…Consequently, the following mechanism for the Rh (III)-catalysed [4 + 2] annulation protocol is proposed on the basis of our current results and the results of previously reported studies (Scheme 3). [2,[4][5][6][7] Initially, activation of the [Cp*RhCl 2 ] 2 species with the aid of a base forms the active [Cp*Rh(III)] species, [5][6][7] which subsequently undergoes insertion at the C(sp 2 )À H bond in aromatic oxime 1 a to generate the Cp*Rh III complex A. Coordination of the Cp*Rh III complex A with alkene 2 followed by insertion across the C=C bond to produce the seven-membered rhodacycle C. The intermediate C possibly undergoes reductive elimination to give the intermediate D [5a,7] and a Rh I species.…”