Asymmetric borylation of α,β-unsaturated esters catalyzed by novel ring expanded N-heterocyclic carbenes based on chiral 3,4-dihydro-quinazolinium compoundsElectronic supplementary information (ESI) available: NMR spectra of compounds 5 and intermediates. Spectra of enantiomeric excess measurement. See DOI: 10.1039/c4ob01101e

A series of chiral 6-membered ring N-heterocyclic carbene (NHC) precursors based on 3,4-dihydro-quinazoline were synthesized with overall yields of 54-62%. NHCs generated from these precursors show excellent asymmetric catalytic properties for borylation of α,β-unsaturated esters with enantioselectivity of up to 93% with a catalyst content of only 1 mol%. A series of novel ring expanded N-heterocyclic carbene (NHC) precursors were synthesized, which showed excellent enantioselectivities for borylation of α,β-unsaturated esters.