Asymmetric catalytic aziridination of dihydronaphthalenes for the preparation of substituted 2-aminotetralins

Abstract

An enantioselective synthesis of substituted 2-aminotetralins from dihydronaphthalenes in four steps is described. The key step is the Jacobsen's (diimine)copper–catalyzed asymmetric aziridination of dihydronaphthalenes to the respective aziridines in 33 – 82% yields and 60 – 87% enantiomeric excess. The enantioselectivity and the yield were dependent on the properties of the nitrene precursor. pTsN=IPh appeared in general to give better results than pNsN=IPh. Aziridines were ring-opened in the benzylic position by catalytic hydrogenolysis in quantitative yields, and deprotected in two steps to the respective 2-aminotetralins in 66 – 85% yields. The synthesis of ( S)-2-aminotetralin (>98% ee) and ( S)-2-amino-7-methoxytetralin (56% ee) were accomplished in 30 and 52% overall yields, respectively.