Angel Suárez-Sobrino

A Simple Metal-Promoted Three-Step Access to n/5/m Angular Carbocyclic Systems

A simple three-step access to n/5/m angular tricyclic skeleta from terminal cycloalkenylacetylenes, Cr(CO)(6), and propargylmalonate esters is described. The process involves a cyclopentannulation of propargylmalonates and enynyl Fischer carbenes, followed by a metal-promoted Cope-type fragmentation of the propargyl unit. The resulting 4-allenyl-carbonyl derivatives can undergo either a 5-exo annulation via a tin enolate or an unprecedented gold catalyzed 6-endo cyclization.

Nucleophilic addition/double cyclization cascade processes between enynyl Fischer carbene complexes and alkynyl malonates.

Two new selective cascade processes for enynyl Fischer carbene complexes 1 are described in their reaction with alkynyl malonates. When carbene complexes 1 react with the sodium enolate of homopropargyl malonates 3 a consecutive Michael-type addition/cyclopentannulation/6-exo cyclization takes place leading, in a regio- and stereoselective way, to n/5/6 angular tricyclic compounds 5. Furthermore, when propargylic malonates are used, a delayed protonation of the reaction mixture allows intermediate 1,4-addition adduct Ia to evolve through a 5-exo cyclization, consisting of an intramolecular nucleophilic attack from the central carbon of the allenylmetallate over the triple C-C bond. Further spontaneous cyclopentannulation of the resulting metallatriene gives rise to bicyclic and linear polycyclic compounds 6 and 7, some of them bearing a polyquinane framework.

Chiral 2-alkoxy-1,3-butadienes: synthesis and face-selectivity in Diels–Alder reactions

Chiral 2-alkoxy-1,3-butadienes are prepared from chiral alcohols, prop-2-ynyltriphenylphosphonium bromide and aldehydes; they undergo [4 + 2] cycloadditions to carbo- and hetero-dienophiles with moderate to high face-selectivity.