Click chemistry in CuI-zeolites: the Huisgen [3 + 2]-cycloaddition.

[reaction: see text] CuI-exchanged solids based on zeolite materials were investigated for the first time as catalysts in organic synthesis. The catalytic potential of these materials was evaluated in the Huisgen [3 + 2]-cycloaddition. Five CuI-exchanged zeolites were examined and CuI-USY proved to be a novel and efficient heterogeneous ligand-free catalyst for this "click chemistry"-type transformation.

Neopentane and solid acids: direct hydron exchange before cracking.

The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed the C-H bond has appeared favorably involved in the activation of neopentane compared to the less accessible C-C bond. The transition state allowing hydron exchange is most likely a carbonium species (pentacoordinated carbon) as in the case of the H/D exchange between methane and solid acid. The activation energies of the H/D exchange between neopentane and zeolites are the same for all zeolites indicating a common carbonium ion type transition state. On the basis of previous results in the case of the exchange between methane and liquid superacids, the deuterium exchange rates in neopentane were tentatively related to the acidity of the solids. However the order of activity MOR > MFI > BEA > FAU seems to be related to the size of the pores, which may suggest the involvement of a confinement effect in the zeolites cavities. Moreover we found that H/D exchange takes also place between neopentane and deuterated sulfated zirconia (SZ) emphasizing its strong acidity.

Concise synthesis and voltammetric studies of dielsiquinone, a cytotoxic azaanthraquinone.

We have developed a concise synthesis of dielsiquinone 1, a potent cytotoxic agent related to anthraquinones. Electrochemical studies have shown that dielsiquinone is reduced to a semiquinone radical that does not react with O2 to generate toxic reactive oxygen species. These results strongly suggest that 1 should be less cardiotoxic than anthracyclines used in clinic and may therefore provide the basis for the development of safer anticancer drugs.