Stereoselective One‐Pot Synthesis of 1‐Aminoindanes and 5,6‐Fused Azacycles Using a Gold‐Catalyzed Redox‐Pinacol‐Mannich‐Michael Cascade

Yeom, Hankil; Lee, Youngun; Jeong, Jee–Heon; So, Eunsoo; Hwang, Soojin; Lee, Jieun; Lee, Shim Sung; Shin, Seunghoon

doi:10.1002/anie.200906346

Cited by 152 publications

(21 citation statements)

References 58 publications

(4 reference statements)

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“…23 Later studies by Davies, 29,30 Shin, 24,25,39 and Liu 17,40 using different tethered oxidants lent further support for the validity of this intramolecular strategy and led to the development of a plethora of useful synthetic methods.…”

Section: Intramolecular Alkyne Oxidationmentioning

confidence: 96%

“…In this Account, I will discuss our results based both on intramolecular alkyne oxidation and on intermolecular oxidation, with the latter being the focus. I am, however, obligated to point out here that many other researchers including Liu, 17−22 Toste, 23 Shin, 24,25 Zhang, 26−28 Davies, 29−31 Gagosz, 32 Hashmi, 33,34 Li, 35 and Liu 36 have also made outstanding contributions in this field, which will not be discussed due to the nature of this Account.…”

Section: Introductionmentioning

confidence: 99%

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A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

2014

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For the past dozen years, homogeneous gold catalysis has evolved from a little known topic in organic synthesis to a fully blown research field of significant importance to synthetic practitioners, due to its novel reactivities and reaction modes. Cationic gold(I) complexes are powerful soft Lewis acids that can activate alkynes and allenes toward efficient attack by nucleophiles, leading to the generation of alkenyl gold intermediates. Some of the most versatile aspects of gold catalysis involve the generation of gold carbene intermediates, which occurs through the approach of an electrophile to the distal end of the alkenyl gold moiety, and their diverse transformations thereafter. On the other hand, α-oxo metal carbene/carbenoids are highly versatile intermediates in organic synthesis and can undergo various synthetically challenging yet highly valuable transformations such as C–H insertion, ylide formation, and cyclopropanation reactions. Metal-catalyzed dediazotizations of diazo carbonyl compounds are the principle and most reliable strategy to access them. Unfortunately, the substrates contain a highly energetic diazo moiety and are potentially explosive. Moreover, chemists need to use energetic reagents to prepare them, putting further constrains on operational safety.In this Account, we show that the unique access to the gold carbene species in homogeneous gold catalysis offers an opportunity to generate α-oxo gold carbenes if both nucleophile and electrophile are oxygen. Hence, this approach would enable readily available and safer alkynes to replace hazardous α-diazo carbonyl compounds as precursors in the realm of gold carbene chemistry.For the past several years, we have demonstrated that alkynes can indeed effectively serve as precursors to versatile α-oxo gold carbenes. In our initial study, we showed that a tethered sulfoxide can be a suitable oxidant, which in some cases leads to the formation of α-oxo gold carbene intermediates. The intermolecular approach offers excellent synthetic flexibility because no tethering of the oxidant is required, and its reduced form is not tangled with the product. We were the first research group to develop this strategy, through the use of pyridine/quinolone N-oxides as the external oxidants. In this manner, we can effectively make a C–C triple bond a surrogate of an α-diazo carbonyl moiety in various gold catalyses. With terminal alkynes, we demonstrated that we can efficiently trap exclusively formed terminal carbene centers by internal nucleophiles en route to the formation of cyclic products, including strained oxetan-3-ones and azetidin-3-ones, and by external nucleophiles when a P,N-bidentate ligand is coordinated to gold. With internal alkynes, we generated synthetically useful regioselectivities in the generation of the α-oxo gold carbene moiety, which enables expedient formation of versatile enone products. Other research groups have also applied this strategy en route to versatile synthetic methods. The α-oxo gold carbenes appear to be more electrophilic...

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Section: Intramolecular Alkyne Oxidationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

2014

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“…1 A particularly important class of nucleophiles is oxidant that possesses a nucleophilic oxygen and can formally deliver the oxygen atom during the reaction, and this type of gold-catalyzed alkyne oxidation has been proposed to generate a reactive α-oxo gold carbene intermediate, which would undergo an array of versatile transformations (Equation 1). 2 Early studies in this area use tethered oxidants such as sulfoxide, 3 nitrone, 4 epoxide, 5 nitro, 6 and amine N -oxide, 7 and recently one of us has used pyridine/quinoline N -oxides as external oxidants to achieved intermolecular alkyne oxidation. 8 While α-oxo gold carbenes have been invoked as reactive intermediates in many of these studies, studies using external arylsulfoxides 9 argue against such intermediacy.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Gold(I)-Catalyzed Rearrangements of Acetylenic Amine-N-Oxides: Computational Investigations Lead to a New Mechanism Confirmed by Experiment

et al. 2011

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Quantum mechanical studies of the mechanism of gold-catalyzed rearrangements of acetylenic amine-N-oxides to piperidinones or azepanones have revealed a new mechanism involving a concerted hetero-retroene reaction, formally a 1, 5 hydrogen shift from the N-alkyl groups to the vinyl position of a gold-coordinated methyleneisoxazolidinium or methyleneoxazinanium. Density functional calculations (B3LYP, B3LYP-D3) on the hetero-retroene mechanism reproduce experimental regioselectivities and provide an explanation as to why the hydrogen is transferred from the smaller amine substituent. In support of the proposed mechanism, new experimental investigations show that the hydrogen shift is concerted and that gold carbenes are not involved as reaction intermediates.

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“…Many researchers including us have subsequently applied this intramolecular strategy to other oxygen-delivering oxidants including nitrone, 6 N -oxides, 7 epoxide 8 and nitro 9 successfully, under the assumption 10 that α-oxo gold carbenes were generated.…”

Section: Introductionmentioning

confidence: 99%

[3,3]-Sigmatropic Rearrangement versus Carbene Formation in Gold-Catalyzed Transformations of Alkynyl Aryl Sulfoxides: Mechanistic Studies and Expanded Reaction Scope

Wang

et al. 2013

J. Am. Chem. Soc.

137

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Gold-catalyzed intramolecular oxidation of terminal alkynes with an arenesulfinyl group as the tethered oxidant is a reaction in gold chemistry of high impact, as it introduced to the field the highly-valued concept of gold carbene generation via alkyne oxidation. The proposed intermediacy of α-oxo gold carbenes in these reactions, however, has never been substantiated. Detailed experimental studies suggest that the involvement of such reactive intermediates in the formation of dihydrobenzothiepinones is highly unlikely. Instead, a [3,3]-sigmatropic rearrangement of the initial cyclization intermediate offers a reaction path that can readily explain the high reaction efficiency and the lack of sulfonium formation. With internal alkyne substrates, however, the generation of a gold carbene species becomes competitive with the [3,3]-sigmatropic rearrangement. This reactive intermediate, nevertheless, does not proceed to afford the Friedel-Crafts type cyclization product. Extensive Density Functional Theory studies support the mechanistic conclusion that the cyclized product is formed via an intramolecular [3,3]-sigmatropic rearrangement instead of the previously proposed Friedel-Crafts type cyclization. With the new mechanistic insight, the product scope of this versatile formation of mid-sized sulfur-containing cycloalkenones has been expanded readily to various dihydrobenzothiocinones, a tetrahydrobenzocyclononenone, and even those without the entanglement of a fused benzene ring. Besides gold, Hg(OTf)2 can be an effective catalyst, thereby offering a cheap alternative for this intramolecular redox reaction.

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Stereoselective One‐Pot Synthesis of 1‐Aminoindanes and 5,6‐Fused Azacycles Using a Gold‐Catalyzed Redox‐Pinacol‐Mannich‐Michael Cascade

Cited by 152 publications

References 58 publications

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

A Non-Diazo Approach to α-Oxo Gold Carbenes via Gold-Catalyzed Alkyne Oxidation

Mechanism of Gold(I)-Catalyzed Rearrangements of Acetylenic Amine-N-Oxides: Computational Investigations Lead to a New Mechanism Confirmed by Experiment

[3,3]-Sigmatropic Rearrangement versus Carbene Formation in Gold-Catalyzed Transformations of Alkynyl Aryl Sulfoxides: Mechanistic Studies and Expanded Reaction Scope

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