Diversity in Gold- and Silver-Catalyzed Cycloisomerization of Epoxide−Alkyne Functionalities

Lin, Guorong; Li, Chia‐Wen; Hung, Siao-Hua; Liu, Rai‐Shung

doi:10.1021/ol802047g

Cited by 122 publications

(50 citation statements)

References 33 publications

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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%

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%

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

2014

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“…However, no desired product 3a was observed (Table 1, entry 1). When using a combination of 5 mol % of ( t- Bu) 2 ( o -diphenyl)PAuCl and AgOTf as catalyst, the corresponding product 3a was obtained in 25% yield (Table 1, entry 2) (a small amount of silver salt may have remained in the reaction system when the mol ratio of silver salt to gold complex was 1:1, see [45]). Upon further increase of the AgOTf loading to 10 mol %, the corresponding product 3a was formed in 58% yield with a diastereomeric ratio of 5.4:1 (Table 1, entry 3) [46].…”

Section: Resultsmentioning

confidence: 99%

Efficient gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation of unactivated alkenes with α-ketones

Xiao

Liu

Che

2011

Beilstein J. Org. Chem.

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SummaryThe gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation reaction offers a simple and efficient method for the synthesis of pyrrolidine derivatives in moderate to excellent product yields and with moderate to good diastereoselectivities. The reaction conditions and the substrate scope of this reaction are examined, and a possible mechanism involving AgClO4 catalyzed intermolecular N-Michael addition and the subsequent gold(I)-catalyzed hydroalkylation is proposed.

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“…Liu and co-workers independently reported a very similar gold-catalyzed cyclization of 2-alkynyl aryl epoxide 21 to acylindene 22 (Scheme 18) [53]. A deuterium isotopic experiment was conducted to support the intramolecular oxygen transfer mechanism.…”

Section: Reviewmentioning

confidence: 99%

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

Liu¹,

Xu²,

Hammond³

2011

Beilstein J. Org. Chem.

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SummaryDuring the last decade, gold-catalyzed reactions have become a tour de force in organic synthesis. Recently, the gold-, Brønsted acid- or Lewis acid-catalyzed oxygen transfer from carbonyl to carbon–carbon triple bond, the so-called alkyne–carbonyl metathesis, has attracted much attention because this atom economical transformation generates α,β-unsaturated carbonyl derivatives which are of great interest in synthetic organic chemistry. This mini-review focuses on the most recent achievements on gold-catalyzed oxygen transfer reactions of tethered alkynones, diynes or alkynyl epoxides to cyclic enones. The corresponding mechanisms for the transformations are also discussed.

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Diversity in Gold- and Silver-Catalyzed Cycloisomerization of Epoxide−Alkyne Functionalities

Cited by 122 publications

References 33 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

Efficient gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation of unactivated alkenes with α-ketones

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

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