{2,2-[1,1,2,2-Tetramethyl-1,2-ethanediylbis(nitrilomethylidyne)]}bis([phenolato]) nitrido manganese, Mn(saltmen)N

[174092-29-6]  · C20H22MnN3O2  · (MW 391.35)

(reagent used, following activation, as nitrogen atom transfer reagent to alkenes1)

Physical Data: mp >260 °C.

Solubility: slightly soluble in alcohols; soluble in dichloromethane, and most organic solvents.

Preparative Methods: prepared in one pot by mixing saltmen ligand with manganese(II) acetate in methanol followed by addition of aqueous ammonia and subsequent oxidation with Clorox bleach.2

Purification: chromatography over basic alumina and recrystallization from EtOH/hexane.

Handling, Storage, and Precautions: stable to both air and H2O at room temperature. No known toxicity.

The ligand in the nitrido manganese complex is amenable to variation in structure and electronics. The parent Mn(salen)N (1) complex shows poor solubility in most organic solvents (CH2Cl2, EtOAc, MeCN, Et2O).2 When 2,3-diamino-2,3-dimethylbutane is used as the diamine building block [Mn(saltmen)N], solubility in most organic solvents is good. Lau, Komatsu, and Jørgensen reported optically active salen-derivatives possessing C2-symmetry [e.g. (2)].3-6

When the manganese nitride complex is activated, e.g. by trifluoroacetic anhydride or p-toluenesulfonic anhydride, an intermediate metal-bound acylnitrenoid has been proposed.7-14 This putative species is then transferred to alkenes furnishing the corresponding MnIII (saltmen) OTf.

Amination of Enol Ethers

When the manganese nitride complex is activated by TFAA, it reacts with trimethylsilylenol ethers to afford the corresponding a-amido-ketones (1).2 The trifluoroacetyl protecting group can be cleaved under mild conditions.15 Using the chiral complex 2, a-amido-ketones can be prepared enantioselectively (2).5

Glycals derived from pyranoses and furanoses can be transformed in one step diastereoselectively to 2-amido-2-deoxy-sugars (eqs 3 and 4) with the glycals as the limiting reagents.16 The amination reactions display broad tolerance of a wide range of protecting groups including silyl ethers and acetals. This procedure was successfully employed in the synthesis of D-fucosamine.17

Starting from the protected glucal (3), oxazoline (4) can be isolated and subsequently opened in the presence of BF3·OEt2 leading to disaccharides (5).18

Aziridination of Unfunctionalized Alkenes

When the manganese nitride complex is activated by Ts2O in the presence of pyridine, styrenes are converted to N-tosyl-protected aziridines in up to 78% yield and 94% ee (6).3 Addition of pyridine-N-oxide improves yields and enantioselectivities.

The aziridination of conjugated dienes leads selectively to vinylaziridines (7).19 Bisaziridinated products or [1,4]-addition to pyrrolines are not observed.

Ho et al. reported the aziridination of styrenes with manganese nitride complexes activated by TFA or BF3·OEt2 forming unprotected aziridines (8).4 When a chiral manganese nitride complex (5) is employed, the enantioselectivities are very good, although the yields tend to be low (9).

1. Modern Amination Methods; Ricci A., Ed.; Wiley: New York, 2000.
2. Du Bois, J.; Hong, J.; Carreira, E. M.; Day, M. W., J. Am. Chem. Soc. 1996, 118, 915.
3. Minakata, S.; Ando, T.; Nishimura, M.; Ryu, I.; Komatsu, M., Angew. Chem. 1998, 110, 3596; Angew. Chem., Int. Ed. 1988, 30, 364.
4. Ho, C.-M.; Lau, T.-C.; Kwong, H.-L.; Wong, W.-T., J. Chem. Soc., Dalton Trans. 1999, 2411.
5. Svenstrup, N.; Bøgevig, A.; Hazell, R. G.; Jørgensen, K. A., J. Chem. Soc., Perkin Trans. 1 1999, 1559.
6. Jepsen, A. S.; Robertson, M.; Hazell, R. G.; Jørgensen, K. A., Chem. Commun. 1998, 1599.
7. Du Bois, J.; Tomooka, C. S.; Hong, J.; Carreira, E. M., Acc. Chem. Res. 1997, 30, 364.
8. Arshankow, S. I.; Poznjak, A. L., Z. Anorg. Allg. Chem. 1981, 481, 201.
9. Groves, J. T.; Takahashi, T., J. Am. Chem. Soc. 1983, 105, 2073.
10. Bottomley, L. A.; Neely, F., J. Am. Chem. Soc. 1988, 110, 6748.
11. Neely, F.; Bottomley, L. A., Inorganica Chimica Acta 1992, 192, 147.
12. Chang, C. J.; Low, D. W.; Gray, H. B., Inorg. Chem. 1997, 36, 270.
13. Chang, C. J.; Connick, W. B.; Low, D. W.; Day, M. W.; Gray, H. B., Inorg. Chem. 1998, 37, 3107.
14. Doménech, A.; Formentin, P.; García, H.; Sabater, M. J., Eur. J. Inorg. Chem. 2000, 1339.
15. Green, T. W.; Wuts, P. G. M., Protective Groups in Organic Synthesis; Wiley: New York, 1999, p 556.
16. Du Bois, J.; Tomooka, C. S.; Hong, J.; Carreira, E. M., J. Am. Chem. Soc. 1997, 119, 3179.
17. Carreira, E. M.; Hong, J.; Du Bois, J.; Tomooka, C. S., Pure Appl. Chem. 1998, 70, 1097.
18. Czekelius, C.; Carreira, E. M., unpublished results.
19. Nishimura, M.; Minakata, S.; Thongchant, S.; Ryu, I.; Komatsu, M., Tetrahedron Lett. 2000, 41, 7089.

Constantin Czekelius & Erick M. Carreira

Eidgenössische Technische Hochschule Zürich, Zürich Switzerland

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