Controlling factors for C-H functionalization versus cyclopropanation of dihydronaphthalenes.

Rhodium(II)-catalyzed reactions of vinyldiazoacetates with dihydronaphthalenes were systematically studied. These substrates underwent cyclopropanantion and/or the combined C-H activation/Cope rearrangement in good overall yield and with good diastereo- and enantiocontrol. The selectivity of these reactions was profoundly influenced by the nature of the chiral catalyst, the vinyldiazoacetate, and the dihydronaphthalene.

Enantioselective synthesis of substituted indanones from silyloxyallenes.

A new approach for the synthesis of enantioenriched indanones by asymmetric carbonyl-ene/intramolecular Heck cyclization from racemic silyloxyallenes has been developed. The modular procedure affords highly substituted indenes and indanones with excellent chirality transfer from the optically active carbinols. Full transfer of stereochemical information is achieved in the presence of 1,2,2,6,6-pentamethylpiperidine and PdCl(2)(PPh(3))(2) (1 mol %) in DMF under microwave heating.

Divergence of carbonyl ylide reactions as a function of diazocarbonyl compound and aldehyde substituent: dioxolanes, dioxolenes, and epoxides.

The products from dirhodium(II) acetate-catalyzed reactions between diazocarbonyl compounds and a series of benzaldehydes demonstrate the extent of competition between intramolecular and intermolecular trapping of carbonyl ylide intermediates and the electronic effects that govern these transformations. With dimethyl diazomalonate, competition exists between dioxolane and epoxide formation so that with p-anisaldehyde only epoxide formation is observed and with p-nitrobenzaldehyde only 1,3-dioxolane products are formed. With methyl diazoacetoacetate, intramolecular trapping of the intermediate carbonyl ylide results in the sole production of dioxolenes.