New Palladium-Catalysed Intramolecular Coupling Reactions PDF Download

Author: Francesco Mariani
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Languages : en
Pages : 200

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Book Description
Although sygma-aryl and sygma-vinylpalladium(II) complexes are commonly used as electrophiles in C--C bond forming reactions, recent research has demonstrated that the same palladium intermediates can also react with carbon-heteroatom multiple bonds in a nucleophilic manner. Continuing with the interest of our group on the palladium-catalysed intramolecular coupling of aryl halides whit carbonyl compounds, we have expanded our previous findings to substrates containing other carbon-heteroatom multiple bonds. In this context, the first objective of the PhD Thesis has been the study of the dual nature of the sygma-arylpalladium(II) species in aldehyde containing compounds. Thus, after some preliminary studies on the ambiphilic character of the sygma-arylpalladium(II) intermediates involved in the palladium-catalysed intramolecular reactions of (2-iodoanilino)-aldehydes, we have described an efficient new methodology for the synthesis of dibenzo[b, e]azepin-11-ones based on the intramolecular acylation of aryl iodides with aldehydes. Continuing whit our interest in these nucleophilic addition processes, we have developed an efficient methodology for the preparation of a small library of tetrahydroisoquinolin-4-ols based on the palladium-catalysed intramolecular nucleophilic addition of a-(2-iodobenzylamino)- aldehydes. Finally, we have expanded the influence of the heteroatom (nitrogen, oxygen, and sulphur) on the course of the palladium-catalysed intramolecular reactions of aryl iodides and aldehydes having heteroatom--containing tethers. Through an extensive experimental-computational (DFT) study we have concluded that the nature of the heteroatom in the tether is not decisive for the outcome of these reactions. Continuing our research for methodologies that help us to increase the synthetic potential of organopalladium chemistry, we decide to investigate the feasibility of the palladium-catalysed intramolecular coupling of aryl halides and diazoderivatives as a methodology for the synthesis of nitrogen heterocycles. So, the second objective was the study of the Pd-catalysed intramolecular coupling of aryl halides with N-tosylhydrazones and sygma-diazoesters in nitrogen containing substrates. We have found that palladium can be used to catalyse the C(sp3)-H insertion of metal carbenoids derived from sygma-diazoesters to form pyrrolidines through intramolecular assembly of C(sp3)-C(sp3) bonds. This reaction is the first example of palladium-catalyzed C(sp3)-C(sp3) bond assembly starting from diazocarbonyl compounds. The coupling reaction can be catalyzed by both Pd(0) and Pd(II), is regioselective, and shows a broad functional group tolerance.