BINOL-Catalyzed Asymmetric Synthesis of Chiral Heterocycles; Experimental Mechanistic Study of Binol-Catalyzed Conjugate Addition of Vinylboronic Acids to Enones; Enantioselective Synthesis of Diarylalkane Compounds via Binol-Catalyzed Conjugate Addition

Abstract

A BINOL-catalyzed conjugate addition was shown in our laboratory to be compatible with unprotected indole substrates. This was considered to be an advantage over typical organometallic strategies since it allowed the use of mild boron-based nucleophiles. With this well established method, we investigated the synthesis of a variety of chiral heterocyclic compounds. A new method was developed showing great compatibility with different heteroaryl structures. Along with that, a new BINOL catalyst was introduced that exhibited superior catalytic activity to previously used catalysts. As proposed for previous studies, the rate determining step of the transformation was the carbon-carbon bond formation. In another project, we carried out a Hammet plot study to investigate the electronic effects of the aryl groups on the reaction rate. The results provided solid support for the proposal mentioned above. Work in our laboratory showed that heteroaryltrifluoroborates exhibited superior reactivity to boronic acids in the synthesis of chiral bis-heterocycles. Therefore, in the latest project, we made use of aryltrifluoroborates in BINOL catalysis to construct different chiral bis-aryl compounds, whose structures were present in a number of important molecules. As a result, a new strategy was successfully established allowing access to a variety of enantioenriched diarylalkanes.