Synthesis of 3‐Arylindole‐2‐carboxylates <i>via</i> Copper‐Catalyzed Hydroarylation of <i>o</i>‐Nitrophenyl‐Substituted Alkynoates and Subsequent Cadogan Cyclization

Yamamoto, Yoshihiko; Yamada, Satoshi; Nishiyama, Hisao

doi:10.1002/adsc.201000858

Cited by 23 publications

(7 citation statements)

References 44 publications

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“…Cadogan cyclization is known to be a powerful method for transforming nitroaromatic compounds into various types of nitrogen heterocycles. 43 44 The first step was the copper-catalyzed conjugate arylation of 94, which proceeded in MeOH at 28 1C to furnish 95 in 65-79% yields. The second Cadogan cyclization was performed using a molybdenum-catalyzed protocol to give generally high yields of 96.…”

Section: Heterocycle Synthesis Via Palladiumcatalyzed Reductive Heck ...mentioning

confidence: 99%

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes

Yamamoto

2014

Chem. Soc. Rev.

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339

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Transition-metal (TM)-catalyzed hydroarylation reactions of alkynes have received much attention, because they enable the net insertion of alkyne C-C triple bonds into C-H bonds of aromatic precursors, resulting in regio- and stereo-selective formation of synthetically useful arylalkenes. Taking advantage of this feature, TM-catalyzed alkyne hydroarylations have been successfully used for the synthesis of heterocycles. TM-catalyzed alkyne hydroarylations can be classified into three major categories depending on the type of reaction and precursors involved: (1) palladium-catalyzed reductive Heck reactions of alkynes with aryl halides, (2) TM-catalyzed conjugate arylation reactions of activated alkynes with arylboronic acids, and (3) TM-catalyzed aromatic C-H alkenylations with alkynes. This review surveys heterocycle synthesis via TM-catalyzed hydroarylation of alkynes according to the above classification, with an emphasis on the scope and limitations, as well as the underlying mechanisms.

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Section: Heterocycle Synthesis Via Palladiumcatalyzed Reductive Heck ...mentioning

confidence: 99%

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes

Yamamoto

2014

Chem. Soc. Rev.

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339

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“…Although these two methods produce mutually opposite stereoisomers, subsequent Cadogan cyclization is expected to afford the desired indole products irrespective of the stereochemistry of the precursors. Type I route seemed to be promising because we previously reported that the Cu‐catalyzed hydroarylation of 3‐( o ‐nitrophenyl)propiolates with arylboronic acids and subsequent Cadogan cyclization of the resultant 3,3‐diarylacrylate products afforded 3‐arylindole‐2‐carboxylates . However, the synthetic method for ( o ‐nitrophenyl)(trifluoromethyl)alkyne is strictly limited, even though various efficient methods have been developed for the synthesis of (trifluoromethyl)alkynes .…”

Section: Methodsmentioning

confidence: 99%

“…Moreover, the development of a Mo‐catalyzed method enabled to perform the Cadogan cyclization at a lower reaction temperature . We previously synthesized 3‐arylindole‐2‐carboxylates under modified Cadogan conditions using P( n Bu) 3 or the molybdenum catalyst with PPh 3 ; the latter conditions gave better yields . Therefore, the Mo‐catalyzed Cadogan cyclization was applied to the trifluoromethyl‐substituted hydroarylation products.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of 3‐Aryl‐2‐(trifluoromethyl)indoles via Copper‐Catalyzed Hydroarylation and Subsequent Cadogan Cyclization

2017

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The copper-catalyzed hydroarylation of (trifluoromethyl)alkynes with (o-nitrophenyl)boronic acids selectively afforded trisubstituted (trifluoromethyl)alkenes bearing an o-nitrophenyl group. The obtained hydroarylation products were converted into 3-aryl-2-(trifluoromethyl)indoles in high yields via molybdenum-catalyzed Cadogan cyclization. Similarly, the hydroarylation product prepared from (o-nitrophenyl)(trifluoromethyl)alkyne and (p-anisyl)boronic acid also underwent Cadogan cyclization, albeit with a longer reaction time, affording the desired indole product in a high yield.

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“…This could then be oxidized to its fully aromatic counterpart, namely carbazole 31 (88%), upon exposure to 10% Pd on C in diphenyl ether at 210 °C (various attempts to effect the conversion 29 → 31 in a direct manner, or at least in a onepot-process, have been unsuccessful to date). Upon exposure of compound 31 to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) it was oxidized, in 66% yield, to the natural product clauszoline K (32). On the other hand, treatment of compound 31 with BBr 3 effected cleavage of the associated ether residue and, thereby, the formation of the anticipated phenolic product 33 (84%).…”

Section: Carbazolesmentioning

confidence: 99%

“…Since this last compound has previously been converted into kopsihainanine A, the illustrated synthetic sequence constitutes a formal total synthesis of the racemic modification of this alkaloid. While the majority of the title cross-coupling reactions we have studied to date are of the general form shown in Scheme 17, their utility is considerable because of the differing modes of reductive cyclization 12,31,32 that can be applied to the products 85. Thus, as demonstrated in the multitude of settings presented above, when such products incorporate a nitro group, cyclizations using dihydrogen in the presence of various catalysts provide a range of indoles of the general form 86.…”

Section: Formal Total Synthesis Of the Cage-like Alkaloid Kopsihainan...mentioning

confidence: 99%

The Palladium-Catalyzed Ullmann Cross-Coupling Reaction: A Modern Variant on a Time-Honored Process

et al. 2018

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Cross-coupling reactions, especially those that are catalyzed by palladium, have revolutionized the way in which carbon-carbon bonds can be formed. The most commonly deployed variants of such processes are the Suzuki-Miyaura, Mizoroki-Heck, Stille, and Negishi cross-coupling reactions, and these normally involve the linking of an organohalide or pseudohalide (such as a triflate or nonaflate) with an organo-metallic or -metalloid such as an organo-boron, -magnesium, -tin, or -zinc species. Since the latter type of coupling partner is often prepared from the corresponding halide, methods that allow for the direct cross-coupling of two distinct halogen-containing compounds would provide valuable and more atom-economical capacities for the formation of carbon-carbon bonds. While the venerable Ullmann reaction can in principle achieve this, it has a number of drawbacks, the most significant of which is that homocoupling of the reaction partners is a competitive, if not the dominant, process. Furthermore, such reactions normally occur only under forcing conditions (viz., often at temperatures in excess of 250 °C). As such, the Ullmann reaction has seen only limited application in this regard, especially as a mid- to late-stage feature of complex natural product synthesis. This Account details the development of the palladium-catalyzed Ullmann cross-coupling reaction as a useful method for the assembly of a range of heterocyclic systems relevant to medicinal and/or natural products chemistry. These couplings normally proceed under relatively mild conditions (<100 °C) over short periods of time and, usually, to the exclusion of (unwanted) homocoupling events. The keys to success are the appropriate choice of coupling partners, the form of the copper metal employed, and the choice of reaction solvent. At the present time, the cross-coupling partners capable of engaging in the title reaction are confined to halogenated and otherwise electron-deficient arenes and, as complementary reactants, α- or β-halogenated, α,β-unsaturated aldehydes, ketones, esters, lactones, lactams, and cycloimides. Nitro-substituted (and halogenated) arenes, in particular, serve as effective participants in these reactions, and the products of their coupling with the above-mentioned carbonyl-containing systems can be manipulated in a number of different ways. Depending on the positional relationship between the nitro and carbonyl groups in the cross-coupling product, the reduction of the former group, which can be achieved under a range of different conditions, provides, through intramolecular nucleophilic addition reactions, including Schiff base condensations, access to a diverse range of heterocyclic systems. These include indoles, quinolines, quinolones, isoquinolines, carbazoles, and carbolines. Tandem variants of such cyclization processes, in which Raney cobalt is used as a catalyst for the chemoselective reduction (by dihydrogen) of nitro and nitrile groups (but not olefins), allow for the assembly of a range of structurally challenging nat...

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Synthesis of 3‐Arylindole‐2‐carboxylates via Copper‐Catalyzed Hydroarylation of o‐Nitrophenyl‐Substituted Alkynoates and Subsequent Cadogan Cyclization

Cited by 23 publications

References 44 publications

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes

Synthesis of heterocycles via transition-metal-catalyzed hydroarylation of alkynes

Synthesis of 3‐Aryl‐2‐(trifluoromethyl)indoles via Copper‐Catalyzed Hydroarylation and Subsequent Cadogan Cyclization

The Palladium-Catalyzed Ullmann Cross-Coupling Reaction: A Modern Variant on a Time-Honored Process

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