Palladium-catalyzed approaches to carbo- and heterocyclic compounds

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2001-01-01
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Gagnier, Steve
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Richard C. Larock
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Chemistry

The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

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The Department of Chemistry was founded in 1880.

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The palladium-catalyzed annulation of alkenes, 1,3-dienes, and alkynes has been further extended to include the synthesis of alpha-alkylidene-gamma-butyrolactones, indanones, 2-cyclopentenones, and quinolines. In addition, the scope and limitations of a palladium(II)-catalyzed process are presented in which alpha,beta-unsaturated ketones are formed from the corresponding enol silyl ethers.;Chapter 1 is a publication that describes the synthesis of alpha-alkylidene-gamma-butyrolactones via the palladium-catalyzed heteroannulation of acyclic and cyclic 1,3-dienes by alpha-iodo and alpha-bromo acrylic acids. This process has proven to be highly regio- and stereoselective. Annulation predominately occurs on the less hindered end of the diene, and with acyclic dienes the E-isomer is the major product. The success of this process is dependent upon the use of the sterically hindered, electron-rich phosphine ligand D tBPF.;Chapter 2 presents the synthesis of indanones and 2-cyclopentenones by the palladium-catalyzed carbonylative cyclization of unsaturated aryl iodides and dienyl triflates, iodides, and bromides. This cyclization is particularly effective on substrates that contain a terminal olefin. It is likely that this palladium transformation is forming an indenone intermediate, which is coordinated to a palladium hydride species. This palladium hydride can add back across the carbon-carbon double bond to form a palladium enolate, which is protonated by H2O.;Chapter 3 examines the synthesis of quinolines through a palladium-catalyzed iminoannulation of internal alkynes. In order to achieve quinoline product, this annulation process needs to proceed through a 6-endo ring closure. However, this process is in competition with the more favorable 5-exo ring closure, which leads to an isoindole system. While the yields and generality for the synthesis of quinolines are only moderate, the optimization results have proven to be interesting from a mechanistic point of view.;Chapter 4 concerns the synthesis of alpha,beta-unsaturated ketones from the corresponding enol silyl ethers using a catalytic palladium(II) strategy. This palladium(II) procedure is performed using catalytic amounts of Pd(OAc) 2 in DMSO at room temperature and uses O2 as an efficient reoxidant.

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Mon Jan 01 00:00:00 UTC 2001