Oxatriquinane and Oxatriquinacene: Extraordinary Oxonium Ions

摘要

The term "oxonium ion" is freighted with significance and evokes images of fleeting intermediates or highly reactive chemical reagents. Indeed, in terms of isolable oxonium species, trialky-loxonium salts with inert counterions (such as BF_4~- or PF_6~- ) are the most powerful alkylating agents one is likely to encounter in the laboratory. In general, they are prepared either by the reaction of an epoxide with an ether in the presence of a Lewis acid, from orthoformates and ethers via dialkoxy-carbenium salts, by the reaction of diazoalkanes with ethers in the presence of an acid with a non-nucleophilic counterion, or by simple alkylation of ethers with alkyl halides in the presence of Lewis acids or silver salts. Herein, we report the synthesis of oxatriquinane (1) and oxatriquinacene (2), the rigid, tricyclic frameworks of which impart to them properties unheard of in alkyl oxonium ion chemistry.