Generation of an NB Ladder-type Structure by Regioselective Hydroboration of an Alkenyl-Functionalized Quaterpyridine

摘要

An unusual reactivity of 2-(1-alkenyl)-pyridines towards hydroboration with 9H-borabicyclo[3.3.1]nonane (9H-BBN) has been employed to selectively introduce two borane groups into a conjugated quaterpyridine. Quantitative conversion of the substrate was observed with exclusive regioselectivity. A molecular structure that allows intramolecular NB coordination was generated. The effect of the ladder formation on the molecular structure and the electronic properties of the conjugated system have been investigated. The synthetic strategy demonstrated herein offers a facile access to NB ladder-type structures from readily available substrates, and allows to simultaneously introduce several boron centers under mild conditions.