The Syntheses Of Chiral-at-Metal Rh(?) Complex And Its Application In Asymmetric Conjugate Addition Of Unactivated Alkenes

In this dissertation,a new method of chiral-at-metal Rh(?)complex catalyzed asymmetric conjugate addition of unactivated alkenes with ?,?-unsaturated 2-acyl imidazoles has been developed.Furthermore,the synthesis route of chiral-at-metal Rh(?)complex has also been designed and developed.The asymmetric Michael addition reaction of alkenyl nucleophiles to the Michael acceptors is a forceful synthetic protocol that allows for construction of enantiomerically enriched the chiral centers adjacent to an alkenyl moiety.Despite the great synthetic value of this sort of double bond,the catalytic asymmetric addition of alkenyl nucleophiles remains insufficiently explored.Typical protocols to install a vinyl group onto ?,?-unsaturated carbonyl compounds require stoichiometric vinyl organometallic reagents,such as alkenyl boronic acids or boronates,alkenylaluminums,alkenylsilanes,alkenylzirconiums,alkenylstannanes and alkenyl Grignard reagents.Unactivated alkenes have rarely been utilized in asymmetric conjugate addition reactions due to the low nucleophilicity and uncontrolled side reactions.Chiral-at-metal Rh(?)complex directly catalyzed asymmetric conjugate addition of unactivated alkenes with ?,?-unsaturated 2-acyl imidazoles has never been reported before,so we carried out the exploration of this field.Based on the research on rhodium catalyst in our group,we envisioned combining simple alkenes and chiral-at-metal rhodium complex in asymmetric conjugate addition reaction.By investigation of the catalysts,solvents and temperature,the corresponding adducts were obtained with excellent enantioselectivities(up to 92%ee).With the optimized reaction conditions in hand,a prepared chiral-at-metal Rh(?)complex catalyzed highly efficient asymmetric conjugate addition of para-vinylanilines with?,?-unsaturated 2-acyl imidazoles is developed,affording the corresponding adducts in 67-95%yields with 86-95%ee.Remarkably,employing as low as 0.05 mol%of Rh(?)complex as catalyst,a gram scale reaction still afford the desired product in 81%yield with 92%enantioselectivity.The synthesis route of chiral-at-metal Rh(?)complexes has been exploxed.By investigation of the bases,solvents,temperature and accillary ligands,a straightforward,various and flexible synthetic method has been developed.