Jf. Quinn et al., ASYMMETRIC CONSTRUCTION OF 4H-CARBAZOL-4-ONE INTERMEDIATES VIA THE CYCLOHEXADIENONE ANNULATION OF CHIRAL CARBENE COMPLEXES, Organometallics, 16(23), 1997, pp. 4945-4947
The quaternary carbon in a 4H-carbazol-4-one can be introduced with hi
gh stereoprecision. in the cyclohexadienone annulation of a 2-indolyl
chromium carbene complex bearing an imidazolidinone chiral auxiliary.
The chiral complex 12 teas found to exist as atropisomers that were re
adily separated, and each was found to react with the same alkyne to g
ive opposite configurations at the quaternary carbon in the H-4-carbaz
ol-4-one product.