title: Asymmetric Synthesis of 1,2-Diamino-4,5-dimethylcyclohexanes by Zirconium-Catalyzed and -Promoted Reductive Cyclization Reactions.
abstract: The asymmetric synthesis of 1,2-diamino-4,5-dimethylcyclohexanes was achieved by the zirconium-catalyzed and -promoted reductive cyclization of N,N'-di[(S)-1-phenylethyl]-4(R),5(R)-diamino-1,7-octadiene. The reaction of the diene with 5 equiv of butylmagnesium chloride and 0.1 mol % of bis(cyclopentadienyl)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 C(2) symmetry, but the reaction with 4 equiv of dibutylzirconocene in tetrahydrofuran 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 sulfonylation reaction, 1(R),2(R)-di(4-toluenesulfonyl)amino)-4(S),5(S)-dimethylcyclohexane was prepared.
authors.affiliation: Dipartimento di Chimica, Università di Sassari, via Vienna 2, 07100 Sassari, Italy, and Dipartimento di Chimica "G. Ciamician", Università di Bologna, via Selmi 2, 40126 Bologna, Italy.
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Grepioni
authors.forename: Stefano
authors.initials: S
authors.lastname: Grilli
authors.forename: Gianluca
authors.initials: G
authors.lastname: Martelli
authors.forename: Diego
authors.initials: D
authors.lastname: Savoia