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Abstract:The relationship between catalyst structure and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins by a series of chiral Mn (sa1en) complexes (1 -10) was examined. The Xray structures of 5-coordinate complexes 5, 8, of 6-coordinate 9 ([6,6 = -fBu; 4,4 = -tBu]+CIO;), and 10 (6,6 = -fBu; 4.4 = -Br ) were determined. Catalysts 1 -9 were derived from (R,R)-1 ,tdiaminocyclohexane and catalyst 10 from (S,S)-1,2-diphenylethyIenediamine. Catalysts 1-9 differ in the stereoelectronic substitution of the orfho (6,6) and para (4,4) positions of the salicylidene moiety. A comparison between structures 5, 8, and 9 reveals that the ligand geometry around the metal center and the chiral diimine backbone remains remarkably constant in both five-and six-coordinate cyclohexanediamine-derived complexes; in contrast, the salicylidene regions of the complexes display a wide range of conformations. The asymmetric epoxidation of indene and 6-cyano-2,2-dimethylchromene with NaOCl catalyzed by complexes 1 -10 was effected. Systematically increasing the steric bulk on the ortho and vtynordp asymmetric eponidations Cstalysis * manganese complexes * structure elucidation