The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Robert H Grubbs - One of the best experts on this subject based on the ideXlab platform.
-
tandem olefin metathesis Oxidative Cyclization synthesis of tetrahydrofuran diols from simple olefins
Journal of the American Chemical Society, 2016Co-Authors: Peter K Dornan, Robert H GrubbsAbstract:A tandem olefin metathesis/Oxidative Cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific Oxidative Cyclization.
-
Tandem Olefin Metathesis/Oxidative Cyclization: Synthesis of Tetrahydrofuran Diols from Simple Olefins
Journal of the American Chemical Society, 2016Co-Authors: Peter K Dornan, Daniel Lee, Robert H GrubbsAbstract:A tandem olefin metathesis/Oxidative Cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific Oxidative Cyclization.
-
Tandem metathesis- dihydroxylation and metathesis- Oxidative Cyclization reactions
2016Co-Authors: Peter K Dornan, Zachary K. Wickens, Carl M. Blumenfeld, Robert H GrubbsAbstract:Tandem catalysis provides an opportunity to assemble significant mol. complexity via mechanistically distinct reactions with a single catalyst. We have developed a tandem Z- selective cross metathesis - dihydroxylation, and have explored the substrate specificity of the catalytic system. We have also developed a tandem metathesis - Oxidative Cyclization to assemble THF diol motifs. Due to the stereospecificity of the oxidn. step, the product stereochem. is detd. in part by the olefin geometry. The stereochem. of the olefin in turn is detd. by the type of metathesis performed and choice of catalyst. The reaction scope and applications of the Oxidative Cyclization will be explored. Mechanistic comparisons between dihydroxylation and Oxidative Cyclization will also be discussed, specifically with regards to the nature of the ruthenate ester hydrolysis step.
Peter K Dornan - One of the best experts on this subject based on the ideXlab platform.
-
tandem olefin metathesis Oxidative Cyclization synthesis of tetrahydrofuran diols from simple olefins
Journal of the American Chemical Society, 2016Co-Authors: Peter K Dornan, Robert H GrubbsAbstract:A tandem olefin metathesis/Oxidative Cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific Oxidative Cyclization.
-
Tandem Olefin Metathesis/Oxidative Cyclization: Synthesis of Tetrahydrofuran Diols from Simple Olefins
Journal of the American Chemical Society, 2016Co-Authors: Peter K Dornan, Daniel Lee, Robert H GrubbsAbstract:A tandem olefin metathesis/Oxidative Cyclization has been developed to synthesize 2,5-disubstituted tetrahydrofuran (THF) diols in a stereocontrolled fashion from simple olefin precursors. The ruthenium metathesis catalyst is converted into an oxidation catalyst in the second step and is thus responsible for both catalytic steps. The stereochemistry of the 1,5-diene intermediate can be controlled through the choice of catalyst and the type of metathesis conducted. This olefin stereochemistry then controls the THF diol stereochemistry through a highly stereospecific Oxidative Cyclization.
-
Tandem metathesis- dihydroxylation and metathesis- Oxidative Cyclization reactions
2016Co-Authors: Peter K Dornan, Zachary K. Wickens, Carl M. Blumenfeld, Robert H GrubbsAbstract:Tandem catalysis provides an opportunity to assemble significant mol. complexity via mechanistically distinct reactions with a single catalyst. We have developed a tandem Z- selective cross metathesis - dihydroxylation, and have explored the substrate specificity of the catalytic system. We have also developed a tandem metathesis - Oxidative Cyclization to assemble THF diol motifs. Due to the stereospecificity of the oxidn. step, the product stereochem. is detd. in part by the olefin geometry. The stereochem. of the olefin in turn is detd. by the type of metathesis performed and choice of catalyst. The reaction scope and applications of the Oxidative Cyclization will be explored. Mechanistic comparisons between dihydroxylation and Oxidative Cyclization will also be discussed, specifically with regards to the nature of the ruthenate ester hydrolysis step.
Ken S Feldman - One of the best experts on this subject based on the ideXlab platform.
-
Extending Pummerer reaction chemistry. Synthesis of (+/-)-dibromophakellstatin by Oxidative Cyclization of an imidazole derivative.
Organic letters, 2005Co-Authors: Ken S Feldman, Amanda P SkoumbourdisAbstract:The diastereoselective Oxidative Cyclization of a dihydrooroidin derivative is reported. The thioimidate product formed by application of a new variant of the Pummerer reaction serves as a precurso...
-
extending pummerer reaction chemistry synthesis of dibromophakellstatin by Oxidative Cyclization of an imidazole derivative
Organic Letters, 2005Co-Authors: Ken S Feldman, Amanda P SkoumbourdisAbstract:The diastereoselective Oxidative Cyclization of a dihydrooroidin derivative is reported. The thioimidate product formed by application of a new variant of the Pummerer reaction serves as a precurso...
-
Extending Pummerer reaction chemistry. Application to the Oxidative Cyclization of tryptophan derivatives.
Organic letters, 2004Co-Authors: Ken S Feldman, Andrew G KaratjasAbstract:The diastereoselective Oxidative Cyclization of a beta-oxygenated tryptophan derivative is reported. This process, which utilizes a new variant of the Pummerer reaction, may have application in TMC-95A synthesis.
Amanda P Skoumbourdis - One of the best experts on this subject based on the ideXlab platform.
-
Extending Pummerer reaction chemistry. Synthesis of (+/-)-dibromophakellstatin by Oxidative Cyclization of an imidazole derivative.
Organic letters, 2005Co-Authors: Ken S Feldman, Amanda P SkoumbourdisAbstract:The diastereoselective Oxidative Cyclization of a dihydrooroidin derivative is reported. The thioimidate product formed by application of a new variant of the Pummerer reaction serves as a precurso...
-
extending pummerer reaction chemistry synthesis of dibromophakellstatin by Oxidative Cyclization of an imidazole derivative
Organic Letters, 2005Co-Authors: Ken S Feldman, Amanda P SkoumbourdisAbstract:The diastereoselective Oxidative Cyclization of a dihydrooroidin derivative is reported. The thioimidate product formed by application of a new variant of the Pummerer reaction serves as a precurso...
Timothy J. Donohoe - One of the best experts on this subject based on the ideXlab platform.
-
Osmium-Catalyzed Oxidative Cyclization of Dienes and Their Derivatives
The Journal of organic chemistry, 2013Co-Authors: Ben S. Pilgrim, Timothy J. DonohoeAbstract:The development and application of novel methods for accomplishing the synthesis of heterocycles via osmium-catalyzed Oxidative Cyclization onto an alkene is described in this Perspective. Beginning with a fortuitous discovery, an extensive examination of the possible mechanism of Cyclization has been carried out, and the method was continuously developed until it had been transformed into an extremely efficient and powerful new catalytic reaction for the formation of tetrahydrofurans and pyrrolidines with complete control over all aspects of relative and absolute stereochemistry. By working with Os(VI) rather than the more familiar Os(VIII), a highly potent yet mild set of reaction conditions were developed. In addition to the method development studies, this work also sets out some synthetic challenges against which the methodology was tested. Pleasingly, the catalytic Oxidative Cyclization has proved itself to be an efficient and functional group tolerant process that was pivotal to the completion of s...
-
A Novel Oxidative Cyclization onto Vinyl Silanes.
ChemInform, 2011Co-Authors: Timothy J. Donohoe, Paul C. M. Winship, Ben S. Pilgrim, Daryl S. Walter, Cedric K. A. CallensAbstract:A variety of tetrahydrofurans bearing a silyl group at the ring junction is prepared in good yields stereoselectively via a osmium-catalyzed Oxidative Cyclization of appropriate terminal vinyl silanes.
-
New Modes for the Osmium-Catalyzed Oxidative Cyclization
Organic letters, 2010Co-Authors: Timothy J. Donohoe, Jeremy S. Parker, Peter J. Lindsay-scott, Cedric K. A. CallensAbstract:The osmium-catalyzed Oxidative Cyclization of amino alcohol initiators formally derived from 1,4-dienes is an effective method for the construction of pyrrolidines, utilizing a novel reoxidant (4-nitropyridine N-oxide = NPNO). The Cyclization of enantiopure syn- and anti-amino alcohols gives rise to enantiopure cis- and trans-2,5-disubstituted pyrrolidines, respectively. Moreover, the Cyclization of bis-homoallylic amines bearing an exocyclic chelating group is shown to be a complementary method for trans-pyrrolidine formation.
-
A Lewis acid promoted Oxidative Cyclization.
The Journal of organic chemistry, 2009Co-Authors: Timothy J. Donohoe, Paul C. M. Winship, Daryl S. WalterAbstract:Replacing trifluoroacetic acid with a catalytic amount of Lewis acid in the osmium mediated Oxidative Cyclization results in higher yielding reactions that can proceed nearly an order of magnitude faster. The osmium loading can also be reduced to as little as 0.2 mol %. Furthermore, these mildly acidic conditions are capable of tolerating a wide range of acid sensitive protecting groups that are incompatible with previous Cyclization conditions.
-
Pyridine-N-oxide as a mild reoxidant which transforms osmium-catalyzed Oxidative Cyclization.
Angewandte Chemie (International ed. in English), 2008Co-Authors: Timothy J. Donohoe, Katherine M. P. Wheelhouse, Peter J. Lindsay-scott, Paul Alan Glossop, Nash Ian Alun, Jeremy S. ParkerAbstract:(Chemical Equation Presented) The PNOman can: The use of pyridine-N-oxide (PNO) transforms the catalytic Oxidative Cyclization to include the formation of pyrrolidines from N-Z-protected amino alcohols and amino acids (see scheme; Z = PhCH2OCO). This new method expands the scope of the Oxidative Cyclization as illustrated with the synthesis of a range of di- and trisubstituted pyrrolidines with complete control of stereochemistry. © 2008 Wiley-VCH Verlag GmbH and Co. KGaA
