Ruthenium-catalyzed redox- and cycloisomerizations : atom economic syntheses of carbo- and heterocycles
Abstract/Contents
- Abstract
- A facile and 100% regioselective cycloisomerization--6-pi-cyclization method for obtaining pyridines is described. The unsaturated ketones and aldehydes derived from the cycloisomerization of primary and secondary propargyl diynols in the presence of CpRu(MeCN)3PF6 are converted to 1-azatrienes which in turn undergo a subsequent electrocyclization--dehydration to provide pyridines with excellent regiocontrol. The ruthenium-catalyzed cycloisomerization is a mild, atom-economical method for obtaining the requisite dienone and dienal substrates. The cycloisomerization--6-pi-cyclization sequence may be carried out in one pot or in two independent steps. Additionally, the azatriene cyclization may be carried out in 1-3 hours under microwave irradiation or, for more sensitive substrates, at lower temperatures for longer periods of time (6--24 hours at 90 °C). An atom-economical method for the convenient synthesis of tetrahydropyrans and tetrahydrofurans is also described. Enones and enals derived from the [IndRu(PPh3)2Cl]-catalyzed redox-isomerization of primary and secondary propargyl alcohols undergo a subsequent intramolecular conjugate addition to provide cyclic ethers in excellent yields. Lastly, we have developed complementary methods for the transition metal-catalyzed enyne cycloisomerizations of cyclic olefins. By using distinct ruthenium and palladium catalysts, decalins and 7,6-bicycles can be obtained with dichotomous stereochemical outcomes. The change in mechanism that accompanies the change in metal affords trans-fused 1,4-dienes with ruthenium and their cis-fused diastereomers under palladium catalysis. In the reactions under ruthenium catalysis, a coordinating group is required, and acts to direct the metal to the same side of the carbocycle, resulting in the observed trans diastereoselectivity. Subtle changes in the carbocyclic substrate led to the discovery of a heretofore-unobserved mechanistic pathway, providing bicyclic cycloisomerization products under palladium catalysis, tricyclic products under ruthenium catalysis in DMA, and a 1:1 mixture of the two under ruthenium catalysis in acetone. The different coordination requirements of the two paths allow for the reaction to be shuttled through the metallacycle pathway (generating tricyclic products) when DMA is used as a solvent. This method of obtaining these cyclobutene products complements the existing methods for catalyzing the [2+2] cycloaddition of alkynes. While other methods have been demonstrated for larger ring sizes with palladium, and for specific alkyne termini with platinum and gold, this method is unique in its substrate scope. To the best of our knowledge, this is the first example of a [2+2] cycloaddition catalyzed by CpRu(MeCN)3PF6.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Gutierrez, Alicia Carolina | |
|---|---|---|
| Associated with | Stanford University, Department of Chemistry | |
| Primary advisor | Trost, Barry M | |
| Thesis advisor | Trost, Barry M | |
| Thesis advisor | Waymouth, Robert M | |
| Thesis advisor | Wender, Paul A | |
| Advisor | Waymouth, Robert M | |
| Advisor | Wender, Paul A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Alicia Carolina Gutierrez. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Thesis (Ph. D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Alicia Carolina Gutierrez
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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