“…Further ligand screening which includes 2,2′-bipyridine ( L20 ), 1,10-phenanthroline ( L21 ), l -prolines ( L22 and L23 ), picolinic acid ( L24 ), N -oxide ( L25 ), and oxalic diamides ( L26 and L27 ) demonstrated that L15 is the optimal ligand to our target reaction (entry 11 and Table S2). − Then, cyclohexenyl triflate ( 10b ) was subjected to the reaction under the aforementioned conditions (Table S2). In this case, the Cu systems displayed a reversal reactivity toward the ring size of cyclic vinyl triflate, leading to only 41% yield of cyclohexenyl hydrazine 11b in spite of the same reaction conditions described in Table , entry 6.…”