Di- - - 1,2S -2-phenyl-1-cyclohexyl Diazenedicarboxylate

Preparative Methods The title reagent is prepared by reaction of (IR, 2S)-2-phenyl-l-cyclohexanol with excess phosgene in the presence of quinoline to afford a chloroformate which is treated directly with hydrazine monohydrate (0.5 equiv) to afford di-(—)-(IR, 25)-2-phenyl- 1-cyclohexyl diazanedicarboxy-late. Oxidation of the diazanedicarboxylate to the diazenedicarboxylate is then readily effected using N-bromosuccinimide and pyridine (eq 1). 

Purification flash chromatography using hexane-ethyl acetate (9 1) as eluent. 

Handling, Storage, and Precautions store in closed vessels under an inert atmosphere in the refrigerator. Protect from light. 

Azo-ene reactions. The ene reaction provides a powerful method for C-C bond formation with concomitant activation of an allylic C-H bond. A variety of functionalized carbon skeletons can be constructed due to the range of enophiles which can be used. For example, carbonyl compounds give homoallylic alcohols and imino derivatives of aldehydes afford homoallylic amines. The azo-ene reaction offers a method for effecting allylic amination by treatment of an alkene with an azo-diester to afford a diacyl hydrazine which upon N-N cleavage furnishes a carbamate. Subsequent hydrolysis of the carbamate provides an allylic amine. Use of chiral diazenedicarboxylates provides a method for effecting stereoselective electrophilic amination. 

Lewis acid-mediated ene reaction of di- —)- / ,25)-2-phenyl-1-cyclohexyl diazenedicarboxylate with cyclohexene using tin(IV) chloride in dichloromethane at —60 °C for 5 min afforded the azo-ene adduct in 80% yield after purification by flash chromatography (eq 2). The H NMR spectrum of the azo-ene adduct recorded at 380 K in deuterated toluene established the presence of only one diastereomer. Further analysis of the ene adduct by HPLC on a Whatman Partisil 5 normal phase silica column using hexane-ethyl acetate (9 1) as eluent confirmed the presence of only one diastereomer. 

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