Synthesis and Desymmetrization of meso Tricyclic Systems Derived from Benzene Oxide.

Ozonolysis of the Diels-Alder adducts derived from benzene oxides and N-alkylmaleimides resulted in fully substituted, meso bicyclic systems bearing six contiguous stereocenters, isolated as diols upon reductive workup with NaBH4. Variation in the workup allowed for isolation of two different diastereoisomers, through double epimerization of the imide stereocenters. Desymmetrization of the resulting meso diols via asymmetric nucleophilic epoxide opening and acylation reactions provided access to highly substituted, enantioenriched fused rings.

Lewis acid activation of carbodicarbene catalysts for Rh-catalyzed hydroarylation of dienes.

The activation of carbodicarbene (CDC)-Rh(I) pincer complexes by secondary binding of metal salts is reported for the catalytic site-selective hydro-heteroarylation of dienes (up to 98% yield and >98:2 γ:α). Reactions are promoted by 5 mol % of a readily available tridentate (CDC)-Rh complex in the presence of an inexpensive lithium salt. The reaction is compatible with a variety of terminal and internal dienes and tolerant of ester, alkyl halide, and boronate ester functional groups. X-ray data and mechanistic experiments provide support for the role of the metal salts on catalyst activation and shed light on the reaction mechanism. The increased efficiency (120 to 22 °C) made available by catalytic amounts of metal salts to catalysts containing C(0) donors is a significant aspect of the disclosed studies.