REGIOSELECTIVE ROBINSON ANNULATION REALIZED BY THE COMBINED USE OF LITHIUM ENOLATES AND ALUMINUM TRIS(2,6-DIPHENYLPHENOXIDE) (ATPH)

Michael addition of lithium enolates derived from ketones to a variety of alpha, beta-unsaturated ketones was realized in the presence of al uminum tris(2,6-diphenylphenoxide) (ATPH). In this reaction, ATPH can be used as a carbonyl protector of alpha, beta-unsaturated carbonyl su bstrates upon complexation, which facilitates the regioselective 1,4-a ddition of lithium enolates to Michael accepters. Similarly, dianions of beta-dicarbonyl compounds undergo Michael addition smoothly using A TPH as an effective promoter of the reaction. Subsequent regioselectiv e, intramolecular aldol condensation was also demonstrated, leading to bicyclic carbon ring systems. Such systems are difficult to obtain by the Robinson annulation usually performed in protic media.