Regiochemical control of the ring-opening of 1,2-epoxides by means of chelating processes. 3. Aminolysis and azidolysis of the cis- and trans-oxides derived from 4-(benzyloxy)cyclohexene
摘要:
The previously observed regiocontrol of the ring-opening of epoxides bearing a remote polar group such as the title compounds (1 and 2) can also be achieved by metal-assisted methods for the direct aminolysis and azidolysis of epoxides. The appropriate use of the metal-assisted chelating or nonchelating procedures in the ring-opening of cis-epoxide 1 effects practically complete regiocontrol of these reactions, thus leading to regioalternating processes for the aminolysis and the azidolysis of 1.
Lanthanide(III) trifluoromethanesulfonates (triflates), such as Yb(OTf)3, Nd(OTf)3 and Gd(OTf)3, catalyze in a extraordinarily efficient way the aminolysis of 1,2-epoxides, affording the corresponding β-amino alcohols, at room temperature and in a non-protic solvent (CH2Cl2 or toluene), in very good yields. The reactions are completely anti stereoselective and highly regioselective.