Asymmetric Epoxidation Of Dihydronaphthalene With A Synthesized Jacobs

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Asymmetric Epoxidation of Dihydronaphthalene with a Synthesized Jacobsen's


Abstract. 1,2 diaminocyclohexane was reacted with L-(+)-tartaric acid to yield

(R,R)-1,2-diaminocyclohexane mono-(+)-tartrate salt. The tartrate salt was then

reacted with potassium carbonate and 3,5-di-tert-butylsalicylaldehyde to yield

(R,R)-N,N'-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine, which was

then reacted with Mn(OAc)2*4H2O and LiCl to form Jacobsen's catalyst. The

synthesized Jacobsen's catalyst was used to catalyze the epoxidation of

dihydronaphthalene. The products of this reaction were isolated, and it was

found that the product yielded 1,2-epoxydihydronaphthalene as well as



In 1990, professor E.N. Jacobsen reported that chiral manganese

complexes had the ability to catalyze the asymmetric epoxidation of

unfunctionalized alkenes, providing enantiomeric excesses that regularly

reaching 90% and sometimes exceeding 98% . The chiral manganese complex

Jacobsen utilized was [(R,R)-N,N'-Bis(3,5-di-tert-butylsalicylidene)-1,2-

cyclohexanediaminato-(2-)]-manganese (III) chloride (Jacobsen's Catalyst).

(R,R) Jacobsen's Catalyst Jacobsen's catalyst opens up short pathways to

enantiomerically pure pharmacological and industrial products via the

synthetically versatile epoxy function .

In this paper, a synthesis of Jacobsen's catalyst is performed (Scheme

1). The synthesized catalyst is then reacted with an unfunctional alkene

(dihydronaphthalene) to form an epoxide that is highly enantiomerically enriched,

as well as an oxidized byproduct.

Jacobsen's work is important because it presents both a reagent and a

method to selectively guide an enantiomeric catalytic reaction of industrial

and pharmacological importance. Very few reagents, let alone methods, are

known to be able to perform such a function, which indicates the truly

groundbreaking importance of Jacobsen's work.

Experimental Section

General Protocol. 99% L-(+)- Tartaric Acid, ethanol,

dihydronaphthalene and glacial acetic acid were obtained from the Aldrich

Chemical Company. 1,2 diaminocyclohexane (98% mix of cis/trans isomers) and

heptane were obtained from the Acros Chemical Company. Dichloromethane and

potassium carbonate were obtained from the EM Science division of EM Industries,

Inc. Manganese acetate was obtained from the Matheson, Coleman and Bell

Manufacturing Chemists. Lithium chloride was obtained form the JT Baker

Chemical Co. Refluxes were carried out using a 100 V heating mantle (Glas-Col

Apparatus Co. 100 mL, 90 V) and 130 V Variac (General Radio Company). Vacuum

filtrations were performed using a Cole Parmer Instrument Co. Model 7049-00

aspirator pump with a Büchner funnel. For Thin Layer Chromatography (TLC)

analysis, precoated Kodak chromatogram sheets (silica gel 13181 with

fluorescent indicator) were used in an ethyl acetate/hexane (1:4) eluent.

TLC's were visualized using a UVP Inc. Model UVG-11 Mineralight Lamp (Short-wave

UV-254 nm, 15 V, 60 Hz, 0.16 A). Masses were taken on a Mettler AE 100. Rotary

evaporations were performed on a Büchi Rotovapor-R. Melting points were

determined using a Mel-Temp (Laboratory Devices, USA) equipped with a Fluke 51

digital thermometer (John Fluke Manufacturing Company, Inc.). Optical rotations

([a]D) were measured on a Dr. Steeg and Renter 6mbH, Engel/VTG 10 polarimeter.

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