Oxidative Annulation of Acetanilides with Alkynes Catalyzed by Cyclopentadienyl Rhodium(III) Complexes with Pendant Amides

Abstract

It has been established that a cationic cyclopentadienyl (Cp) rhodium(III) complex with a pendant Nphenylcarbamoyl moiety (Cp A1 Rh III ) showed high catalytic activity towards the oxidative [3 + 2] annulation of acetanilides with internal alkynes to produce substituted indoles. Catalytic activity of the Cp A1 Rh III complex in the reactions of symmetric internal alkynes (diphenylacetylene and 6-dodecyne) was higher than that of the Cp*-rhodium(III) complex and comparable to that of a Cp-rhodium(III) complex with two ethoxycarbonyl groups (Cp E Rh III ). On the other hand, the Cp A1 Rh III complex showed significantly higher catalytic activity than the Cp E Rh III complex in the reactions of unsymmetric internal alkynes (1-phenyl-1-propyne and 1-phenyl-1-hexyne). Additionally, the catalytic activity of the Cp A1 Rh III complex in the oxidative tandem [2 + 2 + 2] annulation-lactamization of acetanilides with two unsymmetric electron-deficient internal alkynes (ethtyl 2-butynoate) was also comparable to that of the Cp E Rh III complex.

Formal Lossen Rearrangement/Alkenylation or Annulation Cascade of Heterole Carboxamides with Alkynes Catalyzed by CpRhIII Complexes with Pendant Amides

“…Screening of the leaving groups (4d-f,e ntries 9- Scheme4.Cp A1 Rh III complex-catalyzed reactions of N-(pivaloyloxy)thiophene-carboxamides with internala lkynes. 11)a nd bases (entries [12][13][14] revealed that the use of OPiv and NaOAc furtheri mproves the yield of 6cb (entry 14). The electron-deficient Cp E Rh III complex was also effective for the formation of 6cb (entry 15), but the yield did not exceed that using the Cp A7 Rh III complex (entry 14).…”

“…Subsequently, in 2017, we reported the synthesis of CpRh III complexes bearing a pendant amide moiety (Cp A Rh III ) via the rhodium(I)‐catalyzed [2+2+1] cycloaddition of 1,6‐diynes with cyclopropylideneacetamides, leading to substituted fulvenes, followed by their reductive complexation with RhCl 3 in ethanol . Some of these Cp A Rh III complexes also showed high catalytic activity in the oxidative [3+2] annulation of anilides with internal alkynes . Interestingly, the use of the Cp A Rh III complex in place of the Cp*Rh III complex changed the reaction pathways in the reactions of N ‐pivaloylbenzamides with internal alkynes.…”

“…[12] Some of these Cp A Rh III complexes also showed high catalytic activity in the oxidative [3+ +2] annulationo fa nilides with internal alkynes. [12][13][14] Interestingly,t he use of the Cp A Rh III complexi np lace of the Cp*Rh III complex changed the reaction pathways in the reactions of Npivaloylbenzamides with internal alkynes. The Cp A Rh III complex catalyzed not the previously reported [4+ +2] annulation, which is catalyzed by the Cp*Rh III complex( Scheme3a, right), [15] but the formal Lossen rearrangement/oxidative [ 3 + +2] annulation cascade( Scheme 3a,l eft).…”

Effect of Cp‐Ligand Methylation on Rhodium(III)‐Catalyzed Annulations of Aromatic Carboxylic Acids with Alkynes: Synthesis of Isocoumarins and PAHs for Organic Light‐Emitting Devices

“…[15] In the last decade, efficient catalytic systems with different selectivity based on other transition metal complexes have been also developed. [16,17] Herein we report on the use of the rhodium complexes [Cp*RhCl 2 ] 2 and [CpRhI 2 ] n for the synthesis of π-extended isocoumarins and PAHs using various polyaromatic carboxylic acids (e. g. 1-naphthoic acid, 1-pyrenecarboxylic acid, fluorene-1-carboxylic acid, etc.) as coupling partners.…”

Rhodium‐Catalyzed ortho‐Bromination of O‐Phenyl Carbamates Accelerated by a Secondary Amide‐Pendant Cyclopentadienyl Ligand

“…In our previous reports, electron‐deficient Cp E Rh III and amide‐pendant Cp A Rh III complexes showed high catalytic activity toward the ortho ‐C−H bond functionalization of electron‐rich anilides . We anticipated that these Rh III complexes would show high catalytic activity towards the ortho ‐C−H bond bromination of O‐phenyl carbamates due to their electron‐rich nature.…”