Pedro O. Miranda

A new catalytic Prins cyclization leading to oxa- and azacycles.

A new Prins cyclization process that builds up one carbon-carbon bond, one heteroatom-carbon bond, and one halogen-carbon bond, (in an oxa- and azacycle) relies on an iron catalyst system formed from Fe(acac)3 and trimethylsilyl halide. The method displays a broad substrate scope and is economical, environmentally friendly, and experimentally simple. This catalytic method permits the construction of chloro, bromo and iodo heterocycles, by the suitable combination of iron(III) source, the corresponding trimethylsilyl halide and the solvent, in high yields.

Prins-Type Synthesis and SAR Study of Cytotoxic Alkyl Chloro Dihydropyrans

A series of functionalized tetrahydropyran and dihydropyran derivatives was synthesized by means of a Prins‐type cyclization between unsaturated alcohols and several aldehydes. An unprecedented dimer bearing two 4‐chloro‐5,6‐dihydro‐2H‐pyran scaffolds was obtained in high yield. A panel of three representative human solid tumor cells from diverse origin was used to assess the cytotoxicity of the compounds. Overall, the results show the relevance of the chlorovinyl group in the biological activity, and 2‐alkyl‐4‐chloro‐5,6‐dihydro‐2H‐pyrans represent interesting leads for further chemical modifications and biological studies.

Factors Controlling the Alkyne Prins Cyclization : The Stability of Dihydropyranyl Cations

The relative stability of the intermediates involved in the alkyne Prins cyclization and the competitive 2-oxonia-[3,3]-sigmatropic rearrangement was studied. This rearrangement was shown to occur slowly under typical alkyne Prins cyclization conditions when the allenyl oxocarbenium ion that results from the rearrangement is similar to or higher in energy than the starting alkynyl oxocarbenium ion. The formal 2-oxonia-[3,3]-sigmatropic rearrangement may be disfavored by destabilizing the resultant allenyl oxocarbenium ion or by stabilizing an intermediate dihydropyranyl cation. The trimethylsilyl group as a substituent at the alkyne and electron-withdrawing groups (CH2Cl and CH2CN) located at the alpha-position to the carbinol center are shown to be effective. DFT calculations suggest that these substituents stabilize the dihydropyranyl cations, thus leading to a more uniform reorganization of the electronic density in the ring, and do not have a direct effect on the formally positively charged carbon atom.

β′-Hydroxy-α,β-unsaturated ketones: A new pharmacophore for the design of anticancer drugs. Part 2.†

Novel antiproliferative β′‐acyloxy‐α,β‐unsaturated ketones were obtained by means of an iron(III)‐catalyzed multicomponent domino process (ABB′ 3CR). The most active derivatives displayed GI50 values in the range of 0.5–3.9 μM against a panel of representative human solid tumor cell lines: A2780, SW1573, HBL‐100, T‐47D and WiDr. Analysis of cells following 24 h exposure to these drugs showed cell cycle arrest in the S and G2/M phase, in a dose‐dependent manner. Our data indicate that the β′‐acyloxy‐α,β‐unsaturated ketones cause permanent damage to the cells and induce apoptosis.