First synthesis and crystal structures of chiral 1,3-dienylborates

We report on the synthesis of bicyclic 1,3-dienylborates (1a/1b and 2a/2b), wherein the boron and nitrogen atoms are chiral. The absolute configuratio n of these molecules was established by single X-Ray diffraction studies an d qualitative homonuclear NOE difference spectroscopy. The conformational s tability of these molecules is low at ambient or subambient temperature. Th e diastereomeric berates (2a/2b) were found to be very reactive toward dien ophiles in the Diels-Alder reaction.