Gold-catalyzed intermolecular formal (3+2) cycloaddition of stabilized vinyldiazo derivatives and electronically unbiased allenes.

The reaction of electronically unbiased allenes with alkenyldiazo compounds in the presence of gold catalysts provided alkylidenecyclopentene derivatives resulting from a formal intermolecular (3+2) carbocyclization. A stepwise mechanism involving initial activation of the diazo component and subsequent formation of an allyl cation intermediate has been proposed. This process represents the first intermolecular gold-catalyzed cycloaddition involving non-activated allenes.

Copper(I)-catalyzed [3+1] cycloaddition of alkenyldiazoacetates and iminoiodinanes: easy access to substituted 2-azetines.

The copper(I)-catalyzed reaction of alkenyldiazoacetates and iminoiodinanes affords functionalized azetine derivatives. This process is consistent with the formation of an aziridinyldiazoacetate intermediate, which gives rise to the four-membered heterocycles by metal-catalyzed ring expansion. The resulting azetine structure is a direct precursor of azeditine-2-carboxylic acid derivatives (EWG = electron-withdrawing group).

Direct access to ß-oxodiazo compounds by copper(II)-catalyzed oxidative rearrangement of stabilized vinyl diazo derivatives.

The copper(II)-catalyzed reaction of alkenyldiazo compounds with iodosylbenzene leading to ß-oxodiazo derivatives is reported. This process occurs via an unprecedented 1,2-shift of the diazoacetate function. A selection of the synthetic applications of a representative member of this new class of functionalized diazo derivatives in the regioselective synthesis of substituted 1,4-dicarbonyl compounds is also reported.

Pyridine activation via copper(I)-catalyzed annulation toward indolizines.

The copper(I)-catalyzed regioselective [3 + 2] cyclization of pyridines toward alkenyldiazoacetates leading to functionalized indolizine derivatives is reported. A broad range of pyridine derivatives (including quinoline and isoquinoline) is compatible with this cyclization reaction. The process represents the first successful example of metal-catalyzed cyclization of a π-deficient heterocyclic system with alkenyldiazo compounds.