Resumen de 6-hydroxy-2h-pyran-3 (6h)-one derivatives as versatile reagents in organocatalytic and enantioselective reactions
The work compiled in this manuscript focuses on the use of versatile 6 hydroxy-2H-pyran-3(6H)-one derivatives as useful polifunctionalized reagents in the development of different organocatalytic enantioselective reactions with ¿¿¿-unsaturated aldehydes, in the presence of chiral secondary amine catalysts. In this sense, 5-oxo-5,6-dihydro-2H-pyran-2-yl carboxylates have been employed as suitable substrates to perform a formal [4+2]/elimination process with a wide range of enals, by exploiting the potential of the dienamine activation manifold, through a dynamic kinetic resolution. Additionally, 6-hydroxy-2H-pyran-3(6H)-one was used as an oxygen-pronucleophile that undergoes an oxa-Michael/Michael cascade process with enals, through iminium/enamine activation, also in a dynamic kinetic resolution. Besides, 1-acetoxyisochroman-4-ones have been employed as oxidopyrylium ylide precursors in order to carry out a [5+2] cycloaddition with enals. The reaction occurred in the presence of a chiral pyrrolidine/squaramide bifunctional catalyst and under dienamine activation of the enal, affording oxabicyclo[3.2.1]octanes in excellent results. Finally, and as part of a short stay carried out in the laboratories of Prof. K. A. Scheidt in Northwestern University, I participated in a project directed to the use of a dual activation strategy involving N-heterocyclic carbene catalysis and a second Lewis base to perform an enantioselective [4+3] cycloaddition reaction between enals and in situ generated o-quinone methides.
