Syn-1,2-carboboration of alkynes with borenium cations.

ABSTRACT: The reaction of 8-(trimethylsiloxy)quinoline (QOTMS) with BCl3 and (aryl)BCl2 forms QOBCl2 and QOBCl(aryl). The subsequent addition of stoichiometric AlCl3 follows one of two paths, dependent on the steric demands of the QO ligand and the electrophilicity of the resulting borenium cation. The phenyl- and 5-hexylthienylborenium cations, QOBPh(+) and QOBTh(+), are formed, whereas QOBCl(+) is not. Instead, AlCl3 preferentially binds with QOBCl2 at oxygen, forming QOBCl2 ⋅AlCl3, rather than abstracting chloride. A modest increase in the steric demands around oxygen, by installing a methyl group at the 7-position of the quinolato ligand, switches the reactivity with AlCl3 back to chloride abstraction, allowing formation of  Me 2QOBCl(+). All the prepared borenium cations are highly chlorophilic

SUBMITTER: Cade IA 

PROVIDER: S-EPMC4209141 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature