Biologically active compounds are known to exhibit radically different activities based on their differences in chirality. These activities can readily be exploited by the pharmaceutical industry to develop drugs that cure diseases and promote wellness. The ability to obtain the desired stereocenters within a molecule would naturally be a drug designer’s delight, and of great importance to the pharmaceutical industry [[i]]. Enantiomerically pure epoxides are one of the building blocks for designing complex molecules exhibiting a specific chirality. Asymmetric catalysts, especially Jacobsen's catalysts can be used for efficient enantioselective epoxidation of alkenes [[ii], [iii]]. For example, Jacobsen's catalyst was used to synthesize phenylisoserine, a side chain to the famous anti-cancer drug Taxol [[iv]].
N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III)
chloride, a coordination compound of manganese and a salen-type ligand, is
commonly called as Jacobsen’s catalyst. This compound has two enantiomers, the
(R,R) (Figure 1) - & the (S,S) (Figure 2) enantiomers, which give the
appropriate epoxide product from the starting compound (alkene).
The ligand structure of Jacobsen’s complex can be easily modified for synthesizing catalysts for a wide range of reactions, including epoxide-ring openings, Diels-Alder reactions, and conjugate additions [[vii],[viii]].
For example
1) Aluminium salen complex has been used for the carbonylation of epoxides to obtain beta-lactones [[ix]]
2) Cobalt salen complexes (Figure 3, and 4) have been used in hydrolytic kinetic resolutions (HKR), for example, in resolving racemic epichlorohydrin to R- or S- epichlorohydrin (Figure 5).
Synthesis with Catalysts Pvt. Ltd. (SWC) is the largest manufacturer in India of chiral Jacobsen’s complexes as well cobalt containing Jacobsen’s type complexes in their highest possible purities. SWC has the capabilities to manufacture custom designed metal salen complexes as per user requirement. SWC can also provide consultancy services to help the user in all their process or catalyst requirements. Please get in touch with SWC by visiting www.syntheiswithcatalysts.com or by writing to info@synthesiswithcatalysts.com
References:
[i]) Dalton Transactions. 41 (41):
1563–1602
[ii]) Journal of the American Chemical
Society. 112 (7): 2801–2803
[iii]) Journal of the American Chemical Society. 113 (18): 7063.
[iv]) J. Org. Chem.
57 (15): 4320–4323
[v]) Chem. Rev. 105 (5): 1563–1602
[vi]) Org. Lett. 3 (5): 663–666
[vii]) Acc. Chem.
Res. 33 (6): 421–431
[viii]) Science. 299 (5613): 1691–1693
[ix]) J. Am. Chem.
Soc. 124 (7): 1174–1175
