Biomimetic polyene cyclizations. Participation of the phenylacetylenic group as a terminator and the formation of C/D cis steroidal products

Johnson, William S.; Hughes, Laura E.; Kloek, James A.; Niem, T.; Shenvi, Ashok B.

doi:10.1021/ja00499a040

Cited by 25 publications

(7 citation statements)

References 2 publications

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“…Over the past decades, Brønsted acids exhibited their unique privilege and becamem ore and more commonly used for the carbon-carbon bond-forming reaction. [2] Inspired by biomimetic cationic cyclizations of polyenyne derivatives developed some decades ago and the recent work developed by Yamamoto, [3] we reasoned that the concept of using Brønsted acids could be applied to the cyclization of enynest os ynthesize important cyclicc ompounds,w hich are beyondt raditional electrophilic p-activation catalyzed by metals.W ea ssumed that the carbonyl of alkynee none derivatives can be activated selectively by Brønsted acids to give allylic carbocation I-A.N ext, the alkyne group would attack this carbocation to generate alkenyl cation intermediate I-B, [4] which subsequently could be intercepted by nucleophiles to furnish the desired cyclic compounds (Scheme 1b). Herein, we report an unprecedented and attractive triflic acid-catalyzed method, which is beyond the traditional electrophilic p-activation protocol, to synthesize cyclic compounds.Due to the importance of cyclic 1,5-diketones, [5] which are synthesized from enynes using ar uthenium catalyst,a ss ynthetic synthons, [6] we selectedt his skeleton as our target.…”

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confidence: 99%

Triflic Acid‐Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π‐Activation

Liu

Zhang

2016

Chemistry A European J

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The cyclization of enynes, catalyzed by a transition metal, represents a powerful tool to construct an array of cyclic compounds through electrophilic π-activation. In this paper, we disclose a new and efficient strategy for enynes cyclization catalyzed by triflic acid. The salient features of this transformation includes a broad substrate scope, metal free synthesis, open flask and mild conditions, good yields, ease of operation, low catalyst loading, and easy scale-up to gram scale. A preliminary mechanism study demonstrated that the activation model of the reaction was σ-activation, which is different from the transition-metal-catalyzed enynes cyclization. Our strategy affords a complementary method to the traditional strategies, which use transition-metal catalysts.

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confidence: 99%

Triflic Acid‐Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π‐Activation

Liu

Zhang

2016

Chemistry A European J

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“…Fort he development of this new reaction, we found inspiration in some excellent works on biomimetic cationic cyclizations of polyenyne derivatives developed some decades ago. [5] These works showed that alkynes could serve as the terminating group of polycyclization processes.W e reasoned that this concept could be exploited in am uch simpler way for the development of am ethod for the synthesis of cyclic alkenyl triflates.T hus,w ea ssumed that enyne derivatives such as 3 should react with triflic acid (TfOH) to give the cation 4 (Scheme 1b). This cation could be intercepted by the alkyne to furnish the alkenyl cation 5.…”

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Synthesis of Cyclic Alkenyl Triflates by a Cationic Cyclization Reaction and its Application in Biomimetic Polycyclizations and Synthesis of Terpenes

et al. 2015

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Cyclic alkenyl triflates are useful intermediates in organic synthesis usually synthesized from ketones through a reaction involving enolization and trapping with a triflating agent. This sequence suffers from some stereochemical drawbacks owing to the basic conditions required. Herein, we describe a new acid-mediated cationic cyclization reaction of enyne derivatives (or alkynols) to access cyclic alkenyl triflates. This new atom-economical process is high yielding, scalable, technically very simple, proceeds without the need of any metallic reagent or catalyst, and more importantly, it complements and challenges conventional methodologies. We have also developed new biomimetic cationic cyclization reactions to yield interesting polycyclic compounds. As a demonstration of the potential of this method in the context of total synthesis, we have synthesized two terpenes: austrodoral and pallescensin A. Using the cationic cyclization in the key step of the synthetic routes allowed the synthesis of these natural products in a very simple, concise, scalable, and efficient way.

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“…[5] These works showed that alkynes could serve as the terminating group of polycyclization processes.W e reasoned that this concept could be exploited in am uch simpler way for the development of am ethod for the synthesis of cyclic alkenyl triflates.T hus,w ea ssumed that enyne derivatives such as 3 should react with triflic acid (TfOH) to give the cation 4 (Scheme 1b). [5] These works showed that alkynes could serve as the terminating group of polycyclization processes.W e reasoned that this concept could be exploited in am uch simpler way for the development of am ethod for the synthesis of cyclic alkenyl triflates.T hus,w ea ssumed that enyne derivatives such as 3 should react with triflic acid (TfOH) to give the cation 4 (Scheme 1b).…”

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confidence: 99%

Synthesis of Cyclic Alkenyl Triflates by a Cationic Cyclization Reaction and its Application in Biomimetic Polycyclizations and Synthesis of Terpenes

et al. 2015

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Cyclic alkenyl triflates are useful intermediates in organic synthesis usually synthesized from ketones through ar eaction involving enolization and trapping with at riflating agent. This sequence suffers from some stereochemical drawbacks owing to the basic conditions required. Herein, we describe an ew acid-mediated cationic cyclization reaction of enyne derivatives (or alkynols)toaccess cyclic alkenyl triflates. This new atom-economical process is high yielding,s calable, technically very simple,p roceeds without the need of any metallic reagent or catalyst, and more importantly,i tc omplements and challenges conventional methodologies.W eh ave also developed new biomimetic cationic cyclization reactions to yield interesting polycyclic compounds.Asademonstration of the potential of this method in the context of total synthesis, we have synthesized two terpenes:a ustrodoral and pallescensin A. Using the cationic cyclization in the key step of the synthetic routes allowed the synthesis of these natural products in av ery simple,concise,scalable,and efficient way.

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Biomimetic polyene cyclizations. Participation of the phenylacetylenic group as a terminator and the formation of C/D cis steroidal products

Cited by 25 publications

References 2 publications

Triflic Acid‐Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π‐Activation

Triflic Acid‐Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π‐Activation

Synthesis of Cyclic Alkenyl Triflates by a Cationic Cyclization Reaction and its Application in Biomimetic Polycyclizations and Synthesis of Terpenes

Synthesis of Cyclic Alkenyl Triflates by a Cationic Cyclization Reaction and its Application in Biomimetic Polycyclizations and Synthesis of Terpenes

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