Syntheses via vinyl sulfones. 28. Seven-ring annulation. A linch-pin approach to a tetracyclic precursor of the lathrane diterpenes

Braish, T. F.; Saddler, J. C.; Fuchs, P. L.

doi:10.1021/jo00251a001

Cited by 45 publications

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“…Grignard and lithium additions failed, but the corresponding cerium vinyl reagent worked excellently. 47 In our attempts to functionalize the resulting tertiary allylic alcohol as a xanthate, acetate or a mesylate is where we ran into a major unprecedented obstacle. Regardless of base or conditions we employed (large, small, strong or weak base using low or high temperatures in a range of solvents) an unwanted facile fragmentation took place.…”

Section: Resultsmentioning

confidence: 99%

Evolution of an oxidative dearomatization enabled total synthesis of vinigrol

et al. 2014

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The evolution of the synthetic strategy resulting in a total synthesis of vinigrol is presented. Oxidative dearomatization/intramolecular Diels-Alder cycloaddition has served as the successful cornerstone for all of the approaches. Extensive radical cyclization efforts to form the tetracyclic core resulted in interesting and surprising reaction outcomes, none of which could be advanced to vinigrol. These cyclization obstacles were successfully overcome by using Heck instead of radical cyclizations. The total synthesis features a trifluoroethyl ether protecting group being used for the first time in organic synthesis. The logic of its selection and the group’s importance beyond protecting the C8a hydroxyl group is presented along with a discussion of strategies for its removal. Because of the compact tetracyclic cage the route is built around many unusual reaction observations and solutions have emerged. For example, a first of its kind Grob fragmentation reaction featuring a trifluoroethyl leaving group has been uncovered, interesting interrupted selenium dioxide allylic oxidations have been observed as well as intriguing catalyst and counterion dependent directed hydrogenations.

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Section: Resultsmentioning

confidence: 99%

Evolution of an oxidative dearomatization enabled total synthesis of vinigrol

et al. 2014

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“…32,33 The initially formed alkylthiosulfonium ion easily dissociates to produce a thionium ion and methyl disulfide. 34,35 We reasoned that by converting the hydroxyl group present in the lactone and lactam derived aldol products to the corresponding acetates, it should be possible to promote cyclization of the lactone/lactam carbonyl group onto the resulting thionium ion formed from the DMTSF-induced reaction. Once the dihydrofuran ring has been forged, elimination of acetic acid should proceed readily to furnish the desired cyclic alkoxy and/or amido substituted furans.…”

Section: Resultsmentioning

confidence: 99%

A New Method for the Preparation of 2-Thio Substituted Furans by Methylsulfanylation of γ-Dithiane Carbonyl Compounds

et al. 2002

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Several related methods for the preparation of differentially substituted 2-thiofurans are described. The general procedure involves the formation of a thionium ion from a gamma-dithianyl substituted carbonyl compound followed by cyclization of this reactive intermediate onto the tethered carbonyl group. Two methods for thionium ion generation were explored. One of these involved an acid-catalyzed reaction of beta-ketenedithioacetals, prepared from the condensation of 2,2-bis(methylsulfanyl)acetaldehyde with a variety of ketones. Cyclization followed by loss of methane thiol gave 2-thiofurans 17, 18 and 23, 24 in 70-90% yield. Attempts to prepare 5-heteroatom substituted 2-thiofurans from the corresponding beta-ketenedithioacetal amides or esters were unsuccessful, leading to 1,2-thio rearranged products. A more successful route involved the reaction of beta-acetoxy-gamma-thianyl carbonyl compounds with dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF). Treatment of the dithiane with this reagent resulted in the smooth generation of a thionium ion. Cyclization followed by loss of acetic acid afforded thiofurans 17, 18, 23, 47-49, 51, and 61-64 in 40-100% yield. The N-butenyl substituted thioamido furan furnished a rearranged hexahydropyrroloquinolin-2-one in high yield when heated at 110 degrees C.

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“…The biotransformation products were identified by gas chromatography - mass spectrometry by the use of the MS library Wiley 275 and NIST or by comparisons of their retention times and mass spectra with those of the synthesized reference substances [ 24 , 25 , 26 , 27 , 28 ,29,30]. The relative quantitative yield of each product (in %) was determined as the GC-MS integration area of that product divided by the GC-MS integration area of all products.…”

Section: Methodsmentioning

confidence: 99%

Biotransformation of (1S)-2-Carene and (1S)-3-Carene by Picea abies Suspension Culture

et al. 2011

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Biotransformation of (1S)-2-carene and (1S)-3-carene by Picea abies suspension culture led to the formation of oxygenated products. (1S)-2-Carene was transformed slowly and the final product was identified as (1S)-2-caren-4-one. On the other hand, the transformation of (1S)-3-carene was rapid and finally led to the formation of (1S)-3-caren-5-one and (1S)-2-caren-4-one as equally abundant major products. The time-course of the reaction indicates that some products abundant at the beginning of the reaction (e.g. (1S,3S,4R)-3,4-epoxycarane and (1R)-p-mentha-1(7),2-dien-8-ol) were consumed by a subsequent transformations. Thus, a precise selection of the biotransformation time may be used for a production of specific compounds.

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Syntheses via vinyl sulfones. 28. Seven-ring annulation. A linch-pin approach to a tetracyclic precursor of the lathrane diterpenes

Cited by 45 publications

References 0 publications

Evolution of an oxidative dearomatization enabled total synthesis of vinigrol

Evolution of an oxidative dearomatization enabled total synthesis of vinigrol

A New Method for the Preparation of 2-Thio Substituted Furans by Methylsulfanylation of γ-Dithiane Carbonyl Compounds

Biotransformation of (1S)-2-Carene and (1S)-3-Carene by Picea abies Suspension Culture

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