An enantioselective central-axial-central chiral element transfer process leading to a concise synthesis of (+)-sterpurene: intramolecular Diels-Alder reactions of vinylallene sulfoxides

Gibbs, Richard A.; Bartels, Karin; Lee, Robert W. K.; Okamura, William H.

doi:10.1021/ja00192a033

Cited by 86 publications

(15 citation statements)

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“…Alkynylzinc reagents—prepared by deprotonation of the corresponding terminal alkyne and subsequent transmetalation with ZnCl 2 —underwent rapid cross‐coupling reactions with a variety of allylcyclobutene iodides 17 to obtain conjugated cyclobutenyl acetylenes 22 a – f and 23 a – d in good yields (50–96 %; Scheme ), which showed the potential of this methodology to diversify the pool of previously described CBs. The Sonogashira‐type cross‐coupling of a cyclobutene iodide was previously described by Okamura et al . The resulting cyclobutenyl acetylene was applied to a concise synthesis of (+)‐sterpurene.…”

Section: Resultsmentioning

confidence: 99%

Unsaturated Four‐Membered Rings: Efficient Strategies for the Construction of Cyclobutenes and Alkylidenecyclobutanes

Eisold

Baumann

Kiefl

et al. 2016

Chemistry A European J

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Our recent studies of the diastereo- and enantioselective formation of strained alkylidenecycloalkanes drove us to more-thoroughly investigate the formation of four-membered rings for which only few efficient methods are described. We first developed a strategy to diversify the saturated part of the four-membered ring and applied it to a highly diastereoselective synthesis of more-elaborate alkylidenecyclobutanes, which completed our precedent studies. In parallel, cyclobutene structures were built employing simple organometallic methods and further functionalized to give a diverse range of new substitution patterns, which consequently enriched the pool of cyclobutene-based building blocks.

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Section: Resultsmentioning

confidence: 99%

Unsaturated Four‐Membered Rings: Efficient Strategies for the Construction of Cyclobutenes and Alkylidenecyclobutanes

Eisold

Baumann

Kiefl

et al. 2016

Chemistry A European J

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“…One of the main advantages of the Diels-Alder cycloaddition is the overall understanding of its reactivity, selectivity, and methods for chiral induction. Using vinylallene sulfoxides in the synthesis of sterpurene [49,50], chiral alcohol 99 was coupled to cyclobutenyl iodide 98, then transformed into intermediate 101 through the action of 1 has also been transformed into the core of shiartane type 1 nortriterpenoids (see Scheme 16) [43]. Utilizing the known transformation to 80, sodium hydride and bromide 93 were used to generate scaffold 94.…”

Section: Cyclization Strategies To Hydrindane Coresmentioning

confidence: 99%

“…One of the main advantages of the Diels-Alder cycloaddition is the overall understanding of its reactivity, selectivity, and methods for chiral induction. Using vinylallene sulfoxides in the synthesis of sterpurene [49,50], chiral alcohol 99 was coupled to cyclobutenyl iodide 98, then transformed into intermediate 101 through the action of The work done with 1 has provided a great benefit to total synthesis, but is not without its limitations. As shown, the trans-hydridane, trans-6, is complicated by the open β-face of 5, giving a more facile reduction to lead to the cis-isomer.…”

Section: Cyclization Strategies To Hydrindane Coresmentioning

confidence: 99%

“…One of the main advantages of the Diels-Alder cycloaddition is the overall understanding of its reactivity, selectivity, and methods for chiral induction. Using vinylallene sulfoxides in the synthesis of sterpurene [49,50], chiral alcohol 99 was coupled to cyclobutenyl iodide 98, then transformed into intermediate 101 through the action of PhSCl (see Scheme 17). This intermediate underwent a facile cyclization to afford the desired core, and after treatment with MeMgBr/Ni(dppp)Cl and Na/NH 3 , sterpurene (103) was isolated.…”

Section: Cyclization Strategies To Hydrindane Coresmentioning

confidence: 99%

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Methodology for the Construction of the Bicyclo[4.3.0]nonane Core

Eddy

Ichalkaranje

2016

Molecules

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Abstract:The bicyclo[4.3.0]nonane scaffold, commonly known as a hydrindane, is a common structural motif found in many terpenoid structures and one that remains a challenge for synthetic chemists to elaborate with appropriate regio-and stereo-selectivity. Over the course of the study of terpene natural products, the elaboration of the hydrindane structure has seen progress on the utilization of both old and newer methods to achieve the desired outcomes. This review seeks to serve as a general overview of these methods, and detail specific examples.

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“…Presumably, an intramolecular DielsAlder reaction of diene-allene (AE)-14 accounts for the observed result, thereby shutting down both the [3,3]-sigmatropic (and subsequent Nazarov-type cyclization) and the 4p electrocyclization pathways in favor of a [4 + 2] reaction www.chemeurj.org mode. [16] X-ray diffraction studies (Scheme 4 A and the Supporting Information) allowed the unambiguous structural assignment of tetrahydroindene (AE)-15, [10] which was obtained as a mixture of diastereoisomers ((AE)-15 a and (AE)-15 b). Putatively, the co-existence of the two diastereoisomeric forms (AE)-15 a and (AE)-15 b at room temperature is a result of hindered rotation about the butadiene axis (cf.…”

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confidence: 99%

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

Reisinger

Rivera‐Fuentes

Lampart

et al. 2011

Chemistry A European J

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Cascade reactions are valuable tools for building complex molecular architectures with high efficiency, selectivity, and atom economy. These processes have a proven record in the preparation of natural products and biologically relevant molecules.[1] In a similar manner, cascade transformations would greatly benefit the field of advanced materials science, where they offer opportunities for rapid and divergent synthetic elaboration, thereby expanding the chemical space for functional materials.Allenes are particularly interesting candidates for the development of cascade reactions, given the diversity and specificity of their reaction modes.[2] Our interest in alleno-acetylenic scaffolding prompted us to introduce allenes as building blocks in the construction of three-dimensional chiral carbon-rich structures. To be able to prepare stable alleno-acetylenic chromophores, the 1,3-di-tert-butyl-1,3-diethynylallene (DEA) moiety was developed.[3] The introduction of tert-butyl substituents provides steric hindrance to the allene core, reducing its reactivity considerably. Taking advantage of the kinetic stability of these alleno-acetylenic scaffolds, we were able to resolve their enantiomers, [4] and use them to build enantiopure chiral push-pull chromophores, [4,5] macrocycles, [6] and helical foldamers. [7] Here, we explore the potential of the allene core of DEAs to participate in cascade pericyclic reactions, which lead to highly substituted complex carbon skeletons in a one-pot fashion, with excellent chemo-, regio-, and stereoselectivities. [8] We first investigated the reaction between racemic DEA (AE)-1 and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and 1,1,2,2-tetracyanoethene (TCNE), to give butadienes (AE)-2 a and (AE)-2 b, respectively, by a formal [2 + 2] cycloaddition, followed by cycloreversion (CA/CR).[9] While the reaction with TCNE proceeded cleanly at room temperature, [4] we noticed that when the reaction with TCNQ was carried out at 40 8C, a significant amount of a by-product was formed. Isolation and characterization of this compound showed that adduct (AE)-2 a undergoes a 4p electrocyclization (EC) between the allene core and the proximal dicyanovinyl moiety, to give cyclobutene 3 a (Scheme 1). In a similar way, butadiene (AE)-2 b could be transformed into cyclobutene 3 b, in which water was eliminated from the acetonide protecting group. The molecular structures of cyclobutenes 3 a and 3 b were unambiguously assigned by X-ray diffraction studies (Scheme 1; for details, see the Supporting Information).[10]The triple CA/CR/EC cascade also produced dicyanocyclobutenes 18 and 19 (see Scheme SI1 in the Supporting Information) in high yield (82-87 %) with the acetonide protecting group replaced by an iPr 3 Si substituent. We found that addition of 10 equivalents of trifluoroacetic acid (TFA) accelerates the reaction and increases the yields significantly. It can be inferred that TFA protonates the aniline nitrogen, quenching the intramolecular charge-transfer interaction, and in turn making the dic...

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An enantioselective central-axial-central chiral element transfer process leading to a concise synthesis of (+)-sterpurene: intramolecular Diels-Alder reactions of vinylallene sulfoxides

Cited by 86 publications

References 0 publications

Unsaturated Four‐Membered Rings: Efficient Strategies for the Construction of Cyclobutenes and Alkylidenecyclobutanes

Unsaturated Four‐Membered Rings: Efficient Strategies for the Construction of Cyclobutenes and Alkylidenecyclobutanes

Methodology for the Construction of the Bicyclo[4.3.0]nonane Core

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

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