Resumen de Stereoselective metal-catalyzed transformations for carbon-boron bond formation and carbon-nitrogen bond cleavage
In the first chapter we have made a brief introduction about asymmetric catalysis explaining some of the existing strategies to synthetize chiral product.
In the second chapter, we have developed an enantioselective copper-catalyzed desymmetrization of meso-cyclobutenes for the synthesis of enantiomerically enriched cyclobutylboronates. This was the first catalytic enantioselective synthesis of this family of compounds. Through this methodology we have prepared a broad scope of cyclobutanes with high levels of diastereo- and enantioselectivity with up to four stereogenic centers. We have also developed some strategies to synthetize useful synthetic intermediates from the cyclobutylboronates.
The third chapter of this Doctoral Thesis is divided into two parts. First, we have developed a stereospecific copper-catalyzed substitution reaction of propargylic ammonium salts with aryl Grignard reagents. The reaction was completely -regioselective and stereospecific. Also, the functional group tolerance of the reaction is exceptional. In addition, no added ligand was needed, and we simply used an inexpensive copper salt. In the second part of this chapter, we developed a strategy for the synthesis of enantiomerically enriched allenes using alkyl Grignard reagents instead of aryl Grignard reagents. With this strategy we bypassed the problem of the allene racemization when alkyl magnesium halides are used.
In the last chapter of this thesis, we have developed a new methodology for the allyl-allyl cross-coupling reaction between allylic carbonates or ammonium salts and allyl boronates. The reaction was completely regioselective and stereospecific and we have observed complete inversion in the configuration of the chiral center. We have also developed strategies for the selective functionalization of the different double bonds.
