Highly Selective Nucleophilic 4-Aryl-2,3-allenylation of Malonates

of main observation and conclusion Allenes are a class of very important compounds and the development of straightforward,efficient,and highly enantioselective synthetic strategies for allenes have attracted extensive interests.Along this line,it is well known that aryl-substituted allenes may be readily racemized,thus,difficult to prepare in high ee.Herein,an efficient palladium-catalyzed nucleophilic allenylation of malonates w ith racemic 4-aryl-2,3-butadienyl carbonates has been developed.The selectivity issue of mono-vs.bis-allenylation with 2-non-substituted malonates has been addressed.By utilizing(R)-(-)-DTBM-SEGPHOS(5,5'-bisldi(3,5,-di-t-butyl-A-methoxyphenyOphosphino)-4,4'-bi-l,3-benzodioxole)as a chiral ligand,various aryl-substituted allenes and bisallenes have been prepared with good to excellent yields with high chemoselectivity and enantioselectivity under mild reaction conditions.Au-catalyzed cycloisomerization and APK(allenic Pauson-Khand)reactions affording optically active mono-and bicyclic products have been demonstrated.