Total synthesis of (±)-bruguierol A via an intramolecular [3+2] cycloaddition of cyclopropane 1,1-diester

Hu, Bao; Xing, Siyang; Ren, Jing; Wang, Zhongwen

doi:10.1016/j.tet.2010.05.057

Cited by 44 publications

(18 citation statements)

References 20 publications

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“…Subsequent oxidation of the C–Si bond41 in the presence of NaHCO 3 , based on a procedure developed by Krohn and Khanbabaee,42 affords diol 20 in 84 % overall yield. Catalytic oxidative conversion to lactone 21 (79 % yield),43 followed by methyl addition/Lewis acid‐catalyzed cyclization generates tricyclic 22 (65 % overall yield for the two steps), conversion of which to the natural product has been previously reported 44…”

Section: Resultsmentioning

confidence: 86%

Exceptionally E‐ and β‐Selective NHC–Cu‐Catalyzed Proto‐Silyl Additions to Terminal Alkynes and Site‐ and Enantioselective Proto‐Boryl Additions to the Resulting Vinylsilanes: Synthesis of Enantiomerically Enriched Vicinal and Geminal Borosilanes

Meng

Jang

Hoveyda

2013

Chemistry A European J

144

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An exceptionally site- and E-selective catalytic method for preparation of Si-containing alkenes through protosilylation of terminal alkynes is presented. Furthermore, the vinylsilanes obtained are used as substrates to generate vicinal or geminal borosilanes by another catalytic process; such products are derived from enantioselective protoborations of the Si-substituted alkenes. All transformations are catalyzed by N-heterocyclic carbene (NHC) copper complexes. Specifically, a commercially available imidazolinium salt, cheap CuCl (1.0 mol%) and Me(2)PhSi-B(pin), readily and inexpensively prepared in one vessel, are used to convert terminal alkynes to (E)-β-vinylsilanes efficiently (79-98% yield) and in >98% E and >98% β-selectivity. Vinylsilanes are converted to borosilanes with 5.0 mol% of a chiral NHC-Cu complex in 33-94% yield and up to 98.5:1.5 enantiomeric ratio (e.r.). Alkyl-substituted substrates afford vicinal borosilanes exclusively; aryl- and heteroaryl-substituted alkenes deliver the geminal isomers preferentially. Different classes of chiral NHCs give rise to high enantioselectivities in the two sets of transformations: C(1)-symmetric monodentate Cu complexes are most suitable for reactions of alkyl-containing vinylsilanes and bidentate sulfonate-bridged variants furnish the highest e.r. for substrates with an aryl substituent. Working models that account for the observed trends in selectivity are provided. Utility is demonstrated through application towards a formal enantioselective total synthesis of naturally occurring antibacterial agent bruguierol A.

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Section: Resultsmentioning

confidence: 86%

Exceptionally E‐ and β‐Selective NHC–Cu‐Catalyzed Proto‐Silyl Additions to Terminal Alkynes and Site‐ and Enantioselective Proto‐Boryl Additions to the Resulting Vinylsilanes: Synthesis of Enantiomerically Enriched Vicinal and Geminal Borosilanes

Meng

Jang

Hoveyda

2013

Chemistry A European J

144

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“…Adaptation of the method allowed for construction of the acetal-[n.2.1] skeleton (Scheme 33). 42 124 readily underwent a TESOTf-catalyzed intramolecular [3+2] cycloaddition in nitromethane to generate either acetal products 125 or 4-hydroxycyclohexanones 126 depending on the length of the linker. For linkers with n = 1 and 2, acetals 124 were generated in 28-94% yield.…”

Section: Acetal[n21] Skeletonsmentioning

confidence: 99%

Intramolecular donor–acceptor cyclopropane ring-opening cyclizations

2014

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Cyclization reactions of donor-acceptor (D-A) cyclopropanes are recognized as versatile methods for construction of carbocyclic and heterocyclic scaffolds. In the literature, many examples of these polarized cyclopropanes' reactivity with nucleophiles, electrophiles, and radicals are prevalent. Although intermolecular reactivity of donor-acceptor cyclopropanes is widely reported, reviews that center on their intramolecular chemistry are rare. Thereupon, this tutorial review focalizes on new intramolecular transformations of donor-acceptor cyclopropanes for cycloisomerizations, formal cycloadditions, umpolung reactions, rearrangements and ring-opening lactonizations/lactamizations from 2009 to 2013. Furthermore, the role of D-A acceptor cyclopropanes as reactive subunits in natural product synthesis is underscored.

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“…[2][3][4][5] As important substructures that are prevalent in natural products, cis-2,5-disubstituted tetrahydrofuran/ pyrrolidine and cis-2,6-disubstituted tetrahydropyran/piperidine may also be obtained by CÀC bond cleavage (Scheme 2). [11,12] We also described a novel intramolecular cross-cycloaddition reaction (IMCC) on two types of functionalized cyclopropanes, which were used as all-carbon 1,3-dipoles. Although various cycloaddition and domino reactions have been developed for construction of such bridged skeletons, [6,7] most of them focus on the synthesis of one type or one subclass of the big and structurally diverse family of [n.2.1] and [n.3.1] skeletons, and development of a more general, efficient, and conceptually new strategy still remains important and challenging.…”

mentioning

confidence: 99%

“…[8] Subsequently Zhang and co-workers developed a gold-catalyzed intermolecular [4+2] cycloaddition of ACP ketones with alkenes, carbonyl compounds, and imines. [11,12] We also described a novel intramolecular cross-cycloaddition reaction (IMCC) on two types of functionalized cyclopropanes, which were used as all-carbon 1,3-dipoles. [10] We have recently developed a general strategy for construction of bridged oxa-and aza- [n.2.1] skeletons and have successfully applied it to the total synthesis of platensimycin and bruguierol.…”

mentioning

confidence: 99%

Lewis Acid Catalyzed Intramolecular [4+2] and [3+2] Cross‐Cycloaddition of Alkynylcyclopropane Ketones with Carbonyl Compounds and Imines

et al. 2012

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The structurally diverse and complex family of compounds that have bridged oxa/aza-[n.2.1] and oxa/aza-[n.3.1] skeletons (n = 2, 3, 4) widely occurs in nature and exhibits a broad range of biological activities (Scheme 1). Additionally, such bridged skeletons can also be used as key intermediates in organic synthesis because of their inherent stereochemistry and multiple functionalizable sites. [1] A general strategy for the construction of medium-sized carbocycles may be provided by CÀO or CÀN bond cleavage in bridged skeletons (Scheme 2). [2][3][4][5] As important substructures that are prevalent in natural products, cis-2,5-disubstituted tetrahydrofuran/ pyrrolidine and cis-2,6-disubstituted tetrahydropyran/piperidine may also be obtained by CÀC bond cleavage (Scheme 2). The development of a general strategy to construct such differently bridged skeletons is important for both the synthesis of natural products and the construction of structurally diverse molecular libraries for chemical biology and the discovery of pharmaceutical and agrochemical leads.Cycloaddition and domino reactions belong to the most efficient and direct transformations of cyclic skeletons. Although various cycloaddition and domino reactions have been developed for construction of such bridged skeletons, [6,7] most of them focus on the synthesis of one type or one subclass of the big and structurally diverse family of [n.2.1] and [n.3.1] skeletons, and development of a more general, efficient, and conceptually new strategy still remains important and challenging.Alkynylcyclopropane (ACP) ketone has recently been introduced as a useful all-carbon 1,4-dipole. Zhang and Schmalz reported a Lewis acid (LA) catalyzed domino cycloisomerization/nucleophilic ring-opening process of ACP ketones. [8] Subsequently Zhang and co-workers developed a gold-catalyzed intermolecular [4+2] cycloaddition of ACP ketones with alkenes, carbonyl compounds, and imines. [9a] Some other types of cycloadditions have also been successfully developed by Zhang and co-workers, and by our research group. [10] We have recently developed a general strategy for construction of bridged oxa-and aza-[n.2.1] skeletons and have successfully applied it to the total synthesis of platensimycin and bruguierol. [11,12] We also described a novel intramolecular cross-cycloaddition reaction (IMCC) on two types of functionalized cyclopropanes, which were used as all-carbon 1,3-dipoles. We hoped to apply this IMCC on ACP ketone to develop a [4+2] IMCC as a general strategy for construction of oxa-and aza-[n.3.1] skeletons (Scheme 3). Moreover, the difference between p-electrophilic (p-LAs) and s-electrophilic (s-LAs) LAs was consid-Scheme 1. Representative natural products containing oxa-/aza-[n.2.1] or oxa-/aza-[n.3.1] skeletons. Scheme 2. Oxa-/aza-[n.2.1] or oxa-/aza-[n.3.1] skeletons used as key intermediates in organic synthesis. FG = functional group.

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Total synthesis of (±)-bruguierol A via an intramolecular [3+2] cycloaddition of cyclopropane 1,1-diester

Cited by 44 publications

References 20 publications

Exceptionally E‐ and β‐Selective NHC–Cu‐Catalyzed Proto‐Silyl Additions to Terminal Alkynes and Site‐ and Enantioselective Proto‐Boryl Additions to the Resulting Vinylsilanes: Synthesis of Enantiomerically Enriched Vicinal and Geminal Borosilanes

Exceptionally E‐ and β‐Selective NHC–Cu‐Catalyzed Proto‐Silyl Additions to Terminal Alkynes and Site‐ and Enantioselective Proto‐Boryl Additions to the Resulting Vinylsilanes: Synthesis of Enantiomerically Enriched Vicinal and Geminal Borosilanes

Intramolecular donor–acceptor cyclopropane ring-opening cyclizations

Lewis Acid Catalyzed Intramolecular [4+2] and [3+2] Cross‐Cycloaddition of Alkynylcyclopropane Ketones with Carbonyl Compounds and Imines

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