The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
Hans-joachim Knölker - One of the best experts on this subject based on the ideXlab platform.
-
Cycloadditions of Allylsilanes - Part22.¹ Stereoselective Synthesisof Cyclopentanes and Cyclobutanes by Lewis Acid Promoted [3+2] and [2+2] Cycloadditionsof Allylsilanes
Synlett, 2010Co-Authors: Arndt W. Schmidt, Hans-joachim KnölkerAbstract:The development of Lewis acid promoted [3+2] and [2+2] cycloadditions as a novel methodology for the stereoselective construction of cyclopentanes and cyclobutanes is described. Elegant applications of this methodology to the total synthesis of biologically active terpenoid natural products are presented. 1 Introduction 2 [3+2] Cycloadditions of Allylsilanes 2.1 Synthesis of Silylbicyclo[n.3.0]alkanes 2.2 Synthesis of Silylcyclopentanes 2.3 Domino [3+2] Cycloadditions with Alkynones 2.4 [3+2] Cycloadditions with Cycloalkenones 2.5 Synthesis of Silylspirocyclopentanes 2.6 Asymmetric [3+2] Cycloadditions with Chiral Allylsilanes 3 Transformations of the Silylcyclopentanes 3.1 Conversion of the Silylbicyclo[n.3.0]alkanes into Symmetrical Olefins 3.2 Development of a Modified Fleming-Tamao Oxidation 4 Domino Double [3+2] Cycloaddition/Wagner-Meerwein Rearrangement/Friedel-Crafts Alkylation/Elimination 5 [2+2] Cycloadditions of Allylsilanes 5.1 Mechanism 5.2 Synthesis of (Silylmethyl)cyclobutanes 5.3 Rearrangement of (Silylmethyl)cyclobutanes to Silylcyclopentanes 5.4 Domino [2+2] Cycloadditions with Alkynoic Esters 5.5 Stereospecific [2+2] Cycloadditions 5.6 Modified Fleming-Tamao Oxidation of the (Silylmethyl)cyclobutanes 6 Applications to Natural Product Synthesis 6.1 Angular Triquinanes 6.1.1 (±)-Cameroonanol 6.1.2 (±)-Isocomene and (±)-β-Isocomene 6.2 Cyclobutane Natural Products 6.2.1 (±)-Fragranol 6.2.2 The Oleander Scale Pheromone 7 Conclusion
-
Cycloaddition of allylsilanes. Part 20: Organosilicon-mediated total synthesis of (±)-cameroonanol
Tetrahedron, 2009Co-Authors: Arndt W. Schmidt, Thomas Olpp, Sören Schmid, Anne Jäger, Hans-joachim KnölkerAbstract:Abstract We describe a seven-step total synthesis of the triquinane sesquiterpene (±)-cameroonanol using a Lewis acid-promoted [3+2] cycloaddition of an allylsilane and a modified Fleming–Tamao Oxidation as key reactions.
-
Stereoselective total synthesis of the sesquiterpene (±)-β-isocomene
Synlett, 2007Co-Authors: Arndt W. Schmidt, Thomas Olpp, Elke Baum, Tina Stiffel, Hans-joachim KnölkerAbstract:Application of the Lewis acid mediated [3+2] cycloaddition of allyl- TERT-butyldiphenylsilane combined with a modified Fleming-Tamao Oxidation provides a stereoselective route to the triquinane sesquiterpene (±)-β-isocomene.
-
Stereoselective Total Synthesis of the Sesquiterpene (±)-Cameroonanol
Synlett, 2007Co-Authors: Arndt W. Schmidt, Thomas Olpp, Sören Schmid, Sigrid Goutal, Anne Jäger, Hans-joachim KnölkerAbstract:We describe a stereoselective synthesis of the triquinane (±)-cameroonanol using the Lewis acid mediated [3+2] cyclo-addition of an allylsilane and a modified Fleming-Tamao Oxidation as key steps.
Arndt W. Schmidt - One of the best experts on this subject based on the ideXlab platform.
-
Cycloadditions of Allylsilanes - Part22.¹ Stereoselective Synthesisof Cyclopentanes and Cyclobutanes by Lewis Acid Promoted [3+2] and [2+2] Cycloadditionsof Allylsilanes
Synlett, 2010Co-Authors: Arndt W. Schmidt, Hans-joachim KnölkerAbstract:The development of Lewis acid promoted [3+2] and [2+2] cycloadditions as a novel methodology for the stereoselective construction of cyclopentanes and cyclobutanes is described. Elegant applications of this methodology to the total synthesis of biologically active terpenoid natural products are presented. 1 Introduction 2 [3+2] Cycloadditions of Allylsilanes 2.1 Synthesis of Silylbicyclo[n.3.0]alkanes 2.2 Synthesis of Silylcyclopentanes 2.3 Domino [3+2] Cycloadditions with Alkynones 2.4 [3+2] Cycloadditions with Cycloalkenones 2.5 Synthesis of Silylspirocyclopentanes 2.6 Asymmetric [3+2] Cycloadditions with Chiral Allylsilanes 3 Transformations of the Silylcyclopentanes 3.1 Conversion of the Silylbicyclo[n.3.0]alkanes into Symmetrical Olefins 3.2 Development of a Modified Fleming-Tamao Oxidation 4 Domino Double [3+2] Cycloaddition/Wagner-Meerwein Rearrangement/Friedel-Crafts Alkylation/Elimination 5 [2+2] Cycloadditions of Allylsilanes 5.1 Mechanism 5.2 Synthesis of (Silylmethyl)cyclobutanes 5.3 Rearrangement of (Silylmethyl)cyclobutanes to Silylcyclopentanes 5.4 Domino [2+2] Cycloadditions with Alkynoic Esters 5.5 Stereospecific [2+2] Cycloadditions 5.6 Modified Fleming-Tamao Oxidation of the (Silylmethyl)cyclobutanes 6 Applications to Natural Product Synthesis 6.1 Angular Triquinanes 6.1.1 (±)-Cameroonanol 6.1.2 (±)-Isocomene and (±)-β-Isocomene 6.2 Cyclobutane Natural Products 6.2.1 (±)-Fragranol 6.2.2 The Oleander Scale Pheromone 7 Conclusion
-
Cycloaddition of allylsilanes. Part 20: Organosilicon-mediated total synthesis of (±)-cameroonanol
Tetrahedron, 2009Co-Authors: Arndt W. Schmidt, Thomas Olpp, Sören Schmid, Anne Jäger, Hans-joachim KnölkerAbstract:Abstract We describe a seven-step total synthesis of the triquinane sesquiterpene (±)-cameroonanol using a Lewis acid-promoted [3+2] cycloaddition of an allylsilane and a modified Fleming–Tamao Oxidation as key reactions.
-
Stereoselective total synthesis of the sesquiterpene (±)-β-isocomene
Synlett, 2007Co-Authors: Arndt W. Schmidt, Thomas Olpp, Elke Baum, Tina Stiffel, Hans-joachim KnölkerAbstract:Application of the Lewis acid mediated [3+2] cycloaddition of allyl- TERT-butyldiphenylsilane combined with a modified Fleming-Tamao Oxidation provides a stereoselective route to the triquinane sesquiterpene (±)-β-isocomene.
-
Stereoselective Total Synthesis of the Sesquiterpene (±)-Cameroonanol
Synlett, 2007Co-Authors: Arndt W. Schmidt, Thomas Olpp, Sören Schmid, Sigrid Goutal, Anne Jäger, Hans-joachim KnölkerAbstract:We describe a stereoselective synthesis of the triquinane (±)-cameroonanol using the Lewis acid mediated [3+2] cyclo-addition of an allylsilane and a modified Fleming-Tamao Oxidation as key steps.
Stéphane P. Vincent - One of the best experts on this subject based on the ideXlab platform.
-
Multigram-scale synthesis of l,d-heptoside using a Fleming-Tamao Oxidation promoted by mercuric trifluoroacetate.
Carbohydrate Research, 2016Co-Authors: Tianlei Li, Abdellatif Tikad, Maxime Durka, Stéphane P. VincentAbstract:Abstract An efficient multigram-scale synthesis of methyl 2,3,4,6-tetra-O-benzyl- l -glycero-α- d -manno-heptopyranoside from methyl 2,3,4-tri-O-benzyl-α- d -mannopyranoside is reported. It involves a sequence of Swern Oxidation, Grignard addition and Fleming-Tamao reactions. The resulting scaffold was used as a precursor to design a small library of clickable l -heptosides. This study shows that the use of mercuric bistrifluoroacetate is required both to accelerate and to cleanly perform the Fleming-Tamao Oxidation, without side-reactions.
David J. Williams - One of the best experts on this subject based on the ideXlab platform.
-
Fleming−Tamao Oxidation and Masked Hydroxyl Functionality: Total Synthesis of (+)-Pramanicin and Structural Elucidation of the Antifungal Natural Product (−)-Pramanicin
Journal of Organic Chemistry, 1999Co-Authors: Anthony G. M. Barrett, John Head, Marie L. Smith, Nicholas S. Stock, Andrew J. P. White, David J. WilliamsAbstract:The total synthesis of (+)-pramanicin (41b) is reported, thereby establishing the relative and absolute stereochemistry of the naturally occurring antifungal agent. The key steps involve (i) conjugate addition of the diethyl((diethylamino)diphenylsilyl)zincate to a suitably protected γ-lactam 3 and quenching of the resultant enolate with the α,β-unsaturated γ,δ-epoxy aldehyde 2 (X = H), (ii) Ni(acac)2-catalyzed hydroxylation of a β-dicarbonyl array, and (iii) Fleming−Tamao Oxidation to reveal the masked C-3 hydroxyl group.
William R. Roush - One of the best experts on this subject based on the ideXlab platform.
-
Enantio- and diastereoselective synthesis of N-acetyl dihydrotetrafibricin methyl ester.
Journal of the American Chemical Society, 2013Co-Authors: Philippe Nuhant, William R. RoushAbstract:A highly diastereoselective synthesis of N-acetyl dihydrotetrafibricin methyl ester (34) is described. The synthesis features three enantioselective double allylboration reactions and an intramolecular hydrosilylation/Fleming–Tamao Oxidation sequence to establish seven of the hydroxy-bearing stereocenters of 34. Especially noteworthy is the fragment-assembly double allyboration reaction of 2 and 7 using reagent 3, which provides the advanced intermediate 6 with >20:1 diastereoselectivity.
-
Siloxacyclopentenes as Dienophile-Linked Directing Groups in Intramolecular Diels−Alder Reactions
Organic Letters, 2008Co-Authors: Geoff T. Halvorsen, William R. RoushAbstract:The synthesis and intramolecular Diels−Alder reactions of trienes 5 and 6 with a siloxacyclopentene-constrained dienophile are described. These reactions provide the primary cycloadducts 7 and 8 with high diastereoselectivity. These cycloadducts possess trans-relationships between the ring fusion proton and the adjacent C(1) alkoxy group and can be further elaborated to alcohols 9 and 11 (via protiodesilylation) or to 10 and 12 (via Fleming−Tamao Oxidation) depending on the substitutent R.
-
4,5-Diisopropyl-B-[(E)-[(3‘-menthofuryl)dimethylsilyl]allyl]-1,3,2- dioxaborolane, an Improved Chiral Reagent for the Anti α-Hydroxyallylation of Aldehydes: Application to the Enantioselective Synthesis of (−)-Swainsonine
Journal of Organic Chemistry, 1997Co-Authors: J. A. Hunt And, William R. RoushAbstract:Diisopropyl tartrate-modified (E)-[γ-(furyldimethylsilyl)allyl]boronates 10 and 11 were designed for the enantioselective synthesis of substituted anti-3,4-dihydroxy-1-butenes 9 via the anti-α-hydroxyallylation of aldehydes. The reactions of aldehydes with 10 and 11 provided furyldimethylsilyl-substituted anti-1,2-silanols 12 and 13 with good enantioselectivity (74−82% ee), and the silanols were oxidized to the corresponding anti-1,2-diols 9 by a modified Fleming−Tamao Oxidation protocol. The high reactivity of the (menthofuryl)silane unit toward electrophilic substitution allowed complete protodesilylation of menthofuryl-substituted silanols 13 and subsequent Oxidation to diols 9 in a one-pot operation without competing protodesilylation of the allylsilane unit. However, a two-step protocol was required for the protodesilylation−Oxidation of the less reactive 2-(5-methyl)furyl-substituted silanols 12. Reagents 10 and 11 exhibited similar diastereoselectivity in double asymmetric reactions with three chir...