F. Grepioni et al., Asymmetric synthesis of 1,2-diamino-4,5-dimethylcyclohexanes by zirconium-catalyzed and -promoted reductive cyclization reactions, J ORG CHEM, 64(10), 1999, pp. 3679-3683
The asymmetric synthesis of 1,2-diamino-4,5-dimethylcyclohexanes was achiev
ed by the zirconium-catalyzed and -promoted reductive cyclization of N,N'-d
i[(S)-1-phenylethyl]-4(R),5(R)-diamino-1,7-octadiene. The reaction of the d
iene with 5 equiv of butylmagnesium chloride and 0.1 mol % of bis(cyclopent
adienyl)zirconium dichloride in diethyl ether at 0-20 degrees C gave mainly
the 1(R),2(R)-diamino-4(S),5(S)-dimethylcyclohexane derivative having Ct s
ymmetry, but the reaction with 4 equiv of dibutylzirconocene in tetrahydrof
uran at -78 to -50 degrees C gave prevalently the diastereomer with the 4(R
),5(S) configuration. By reductive cleavage of the auxiliary, followed by s
ulfonylation reaction, 1(R),2(R)-di(4-toluenesulfonyl)amino)-4(S),5(S)-dime
thylcyclohexane was prepared.