Rhodium‐Mediated Decarboxylative Conjugate Addition of Fluorinated Benzoic Acids: Stoichiometric and Catalytic Transformations

Methoxy-Directed Aryl-to-Aryl 1,3-Rhodium Migration

“…As described in Scheme 2, κ 2 -carboxylates 2a and 2b were prepared by reactions between [(cod)Rh(μ-OH)] 2 (cod: 1,4- cyclooctadiene), BIPHEP (2,2′-bis(diphenylphosphino)-1,1′-biphenyl), and 2,6-difluorobenzoic acid ( 1a ) or 2,6- dimethoxybenzoic acid ( 1b ) respectively. As we reported previously, 13a 2,6-difluorobenzoate 2a underwent stoichiometric decarboxylation at 120 °C with 1 equiv of added pyridine in toluene, giving the corresponding arylrhodium(I) complex 4a in quantitative conversion.…”

“…The in situ formed 3a underwent quantitative decarboxylation that was consistent with our previous observation. 13a In sharp contrast, thermolysis of in situ formed κ 1 -2,6- dimethoxybenzoate 3b at 120 °C in toluene did not generate the expected Rh(I) 2,6-dimethoxyphenyl complex by decarboxylation. 14 Instead, a novel “ 1,3-carboxylate migration ” appeared to occur, leading to the formation of κ 1 -2,4- dimethoxybenzoate 4b in 34% yield as the only detectable Rh(I) species by 31 P NMR analysis.…”

“…10 We have previously reported Rh(I)-catalyzed decarboxylative transformations of 2,6-difluorobenzoic acids including conjugate addition, oxidative olefination, 12a and protodecarboxylation. 13 As part of our efforts to gain mechanistic insights into Rh(I)-mediated decarboxylation, we have synthesized (bis)phosphine-ligated Rh(I) benzoate complexes for direct observation of stoichiometric decarboxylation. As described in Scheme 2, κ 2 -carboxylates 2a and 2b were prepared by reactions between [(cod)Rh(μ-OH)] 2 (cod: 1,4- cyclooctadiene), BIPHEP (2,2′-bis(diphenylphosphino)-1,1′-biphenyl), and 2,6-difluorobenzoic acid ( 1a ) or 2,6- dimethoxybenzoic acid ( 1b ) respectively.…”

Asymmetric total synthesis of (−)-lingzhiol via a Rh-catalysed [3+2] cycloaddition

“…The transformation of III to IV can be interpreted as a Conia-ene 57 -type reaction between the Rhodaenolate species and the allene. Finally, protonolysis [58][59][60] of complex IV with 7a would give product 7b, which contains a [3.3.0] bicyclic ring moiety, together with the regeneration of complex I, which would allow for the completion of the catalytic cycle.…”

Recent Progress in Pd-Catalyzed Decarboxylative Coupling Reactions of (Hetero)aromatic Carboxylic Acids

“…因此, 与传统偶联反应 [1,9] 发展的 Pd 催化脱羧 Heck 反应、Goossen 等 [13] 报道的 Pd/Cu 催化脱羧芳基化反应, 以及 Forgione 和 Bilodeau 等 [14] 实现的 Pd 催化杂环羧酸脱羧的芳基化反应, 引发 了过渡金属催化脱羧偶联反应的一轮发展高峰, 先后实 现了 Pd [3,8] , Cu [15] , Ag [16] , Rh [17] , Au [18] , Fe [19] , Ru [20] 等过 渡金属促进的脱羧偶联反应, 并初步展示了过渡金属促 进的脱羧偶联反应在有机合成等生产领域的强大应 用 [21] .…”