Structure and Reactivity of Boron-Ate Complexes Derived from Primary and Secondary Boronic Esters

Boron-ate complexes derived from primary and secondary boronic esters and aryllithiums have been isolated, and the kinetics of their reactions with carbenium joins studied. The second order rate Constants have been used to derive nucleophilicity parameters for the boron-ate complexes, revealing that nucleophilicity increased with (i) electron donating aromatics On boron, (ii) neopentyl glycol over pinacol boronic esters, and (iii) 12-crown-4 ether.