Diazoacetate, alkylative cyclization

AntiUa and Wulff used axially chiral boron Lewis acids containing 3,3 -diphenyl-2,2 -bi-l-naphthalol (VANOL) and 2,2 -diphenyl-(4-biphenanthrol) (VAPOL) for asymmetric alkylative cyclization between ethyl diazoacetate and A7-benzhydrylimines 169 to obtain aziridine 170 with high yield, excellent cis trans ratio, and enantiomeric excess (Scheme 40.33). ... 

Hubert and co-workers have reported that alkyl diazoacetates react with A -diisopropylcarbodiimide in the presence of transition metal salts to give 2-isopropylimino-3-isopropyl-5-alkoxy-4-oxazolines.115 For example, treatment of ethyl diazoacetate with rhodium(II) acetate in the presence of A,A -diisopropylcarbodiimide (215) produced 2-iso-propylimino-3-isopropyl-5-ethoxy-4-oxazoline (217) in good yield. The formation of oxazoline 217 was interpreted in terms of an addition of ethoxycarbonylcarbene onto one of the nitrogen atoms of the carbodi-imide to give the transient ylide 216 which then cyclized to produce the observed heterocycle. 

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