Synthesis Of Macroporous Organic Boron And Its Application In Small Molecule Activation

Frustrated Lewis pair (FLP) are sterically encumbered Lewis acid and Lewis base combinations, which can not form dative bond. Many examples of such frustrated Lewis pairs are able to react with H2, CO2, alkyne and a variety of other small molecules. In this thesis we synthesized a novel bulky organoborane compound. When combined with amines, the organoborane can form frustrated Lewis pairs and can activate H2and CO2. The following two parts are included in this thesis:1) We successfully synthesized ArF2BH (ArF=2,4,6-tris(trifluoromethyl)phenyl) and found that the deuteride substituted ArF2BD undergoes deuterium/hydrogen exchange under H2(4bar) at50℃. The frustrated Lewis pairs comprised of ArF2BH and NEt3or1,4-diazabicyclo[2.2.2]octane (DABCO) can activate H2at ambient temperature. Theoretical mechanism studies suggest that the Lewis base in FLP can have significant influence on the H2activation mechanism. For "more frustrated" ArF2BH/NEt3, H2is activated in a stepwise manner; and for "less frustrated" ArF2BH/DABCO, H2is activated in a concerted fashion.2) Reactions of secondary amine HNR2(R＝iPr, CH2Ph, Et)/ArF2BH with CO2have been studied. The mixture of ArF2BH and2equiv HNR2(R=’Pr, CH2Ph, Et) can activate CO2to give [H2NR2]’[R2NC(O)OBHArF2]+at ambient temperature. When heating to80℃, ArF2BH and HNR2can react with CO2to afford R2NC(O)OBArF2and liberate one molecule of H2. Furthermore,iPr2NC(O)OBArF2can function as an intramolecular frustrated Lewis pair to cleave H2heterolytically and give formic acid adducts.