Intramolecular frustrated N/B lewis pairs by enamine hydroboration

A series of enamines undergoes anti-Markovnikov hydroboration with Piers' borane HB(C6F5)(2) to yield C-2-bridged frustrated N/B Lewis pairs, featuring weak N center dot center dot center dot B interaction. Some examples show typical frustrated Lewis pair reactions with dihydrogen or with 1-alkynes. One such N/B FLP serves as an active catalyst for the hydrogenation of enamines. Many of the new compounds were characterized by X-ray diffraction.