Browsing by Author "Masood Parvez"

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    Generation of Benzyne Species from Diphenylphosphoryl Derivatives: Simultaneous Exchange of Three Functional Groups
    (European Chemical Societies Publishing, 2016-05-16) Evgueni Gorobets; Masood Parvez; Darren J. Derksen; Brian A. Keay
    Interaction of (2‐diphenylphosphoryl‐3‐iodo‐4‐methoxy‐phenyl) methanol with NaH in DMF at ambient temperature results in the generation of benzyne intermediates that can be trapped by furan or DMF. Trapping with DMF forms 3‐(dimethylaminomethyl)‐2‐hydroxy‐6‐methoxybenzaldehyde demonstrating the simultaneous exchange of three functionalities in a single step. The presence of the alkoxy substituent adjacent to iodine is critical for high regioselectivity addition of DMF. The corresponding bromide or triflate can be used in place of the iodide with equal efficiency. This methodology was used to synthesize the reported structure of gigasol and leading to a structural reassignment of this biscoumarin natural product.
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    Synthesis of the Marine Alkaloid Cylindricine C and Serendipitous Synthesis of Its 2,13-Di-epi Stereoisomer
    (American Chemical Society, 2023-09-18) Arnaud Pastor; Rohen Prinsloo; Kristen N. Burford; Andrew R. Macdonald; Masood Parvez; Chris Gendy; Thomas G. Back
    A new approach to the marine alkaloid cylindricine C afforded its previously unreported (±)-2,13-di-epi stereoisomer as the major product along with a minor amount of the racemic parent alkaloid. Key steps included a stereoselective dianion alkylation of a monoester of 1,2-cyclohexanedicarboxylic acid and an annulation based on the tandem conjugate addition of a primary amine to an acetylenic sulfone, followed by intramolecular acylation of the resulting sulfone-stabilized carbanion. The cis-azadecalin moiety thus formed, comprising the cyclohexane A-ring and enaminone B-ring of the products, was further elaborated by the selenenyl chloride-induced cyclofunctionalization of a pendant butenyl substituent with the enaminone moiety, followed by a seleno-Pummerer reaction. Desulfonylation and enaminone reduction afforded the final products. Molecular modeling and X-ray crystallography provided further insight into these processes.