Infoscience

Thesis

"Palladium-Catalyzed Diamination of Alkynes in Synthesis of Tetracycles" and "Copper-Catalyzed Cyanoalkylation of Unactivated Alkenes"

The thesis deals with the development of transition metal-catalyzed difunctionalization of alkenes and alkynes, which can be categorized into two major topics: (1) palladium-catalyzed diamination of alkynes for the synthesis of tetracycles; (2) copper-catalyzed cyanoalkylation-initiated double functionalization of alkenes. The first part of this thesis describes the synthesis of free NH tetracyclic indoles by palladium-catalyzed diamination of triple bonds. In the presence of palladium catalyst, 1,2-diarylethynes bearing an N-methyl-N-[2-(methoxy-carbonyl)ethyl]amino and an aminocarbonyl/aminosulfonyl group at the ortho positions of the two aromatic rings underwent double cyclization in a highly ordered fashion to afford N-2-(methoxycarbonyl)ethylaed indolo[3,2-c]isoquinolinone or indolobenzothiazine S,S-dioxide with complete chemoselectivity. Subsequently, the N-[2-(methoxycarbonyl)ethyl] group is readily removed under basic conditions (DBU, DMF, 120 °C) to afford tetracycles with indolyl nitrogen unprotected. We subsequently developed a transition metal-free diamination process to access the tetracyclic quindolinones. In the presence of acetic acid and a hydride donor (Hantsch¿s ester) under oxygen atmosphere, double cyclization of 1,3-diarylprop-2-yn-1-ones bearing an N,N-dialkylated amino and an N-monoalkylated amino groups at ortho positions of aromatic rings occurred smoothly to provide tetracyclic quindolinones. In the second part of thesis, copper-catalyzed cyanoalkylative difunctionalization of alkenes with alkylnitriles as alkylative reagents was addressed. We developed catalytic conditions (copper salt, ligand, peroxide, base) that allowed us to convert unactivated alkenes to 1,2-difunctionalized alkanes or its cyclic variants. The domino process proceeded through following key elementary steps: a) generation of cyanolakyl radicals; b) addition of cyanoalkyl radical to unactivated double bond; c) interception of this adduct radical by a suitable reagent, or more frequently, oxidation of adduct radical to carbenium; d) trapping of the carbocation by an internal/or external nucleophile. By applying this strategy, a series of value-added molecules such as dihydroisobenzofurans, gamma-lactones, aziridines and gamma-azidobutyronitriles, were readily synthesized from simple alkenes.

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