Palladium Catalyzed Carbon-carbon Bond Formation at Carbon-hydrogen Bonds PDF Download

Author: Louis-Charles Campeau
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Languages : en
Pages : 0

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Book Description
The biaryl core has been identified by medicinal chemists as a privileged structure in pharmaceutical compounds as it is found in 4.3% of all drugs. For over a century, synthetic chemists have sought new methods for their preparation. Breakthroughs in synthetic catalytic methodology over the past thirty years gave rise to now routine reactions such as the Suzuki and Stille couplings. Unfortunately, the need for pre-activation of both coupling partners makes for wasteful installation and subsequent removal of activating agents. Direct arylation reactions are attractive alternatives to traditional cross-coupling methods, as one of the pre-activated partners is replaced with a simple arene. The organometallic coupling partner is typically replaced as it is the most difficult to prepare. Although the advantages of this approach have made it a popular research topic for more than twenty-five years, no general catalysts exist for this transformation, and in a lot of cases reactivity remains a challenge. This thesis will outline our work in this area of research. First, our efforts toward the development of a general catalyst for the intramolecular direct arylation of aryl halides with simple arenes will be presented. These studies led to the development of three new catalysts for this transformation, affording a process general for aryl chlorides, bromides and iodides. Additionally, mechanistic studies performed on this system have brought to the forefront the concerted metallation-deprotonation mechanistic model for direct arylation. Ultimately, these studies led to the first non-directed intermolecular direct arylation of a simple arene. In a second section, efforts toward the inclusion of pi-deficient heteocycles as a substrate class in direct arylation will be outlined. These studies led to the development of a novel cross-coupling reaction of azine N-oxides with aryl halides. Greater mechanistic understanding, made possible through the use of computational tools, was crucial in extending this methodology to azole N-oxides. Finally, the development of novel direct functionalization reactions with picoline derivatives is described. These substrates are among the first to be suitable for catalyst controlled site-selective functionalization of a sp2 or sp3 C-H bond.