Enantioselective synthesis of(1S,2S)-l,2-di-tert-butyl and(lR,2R)-l,2-di-(l-adamantyl)ethylenediamines

摘要

An enantioselective synthesis of sterically congested 1,2-di-tert-buty and l,2-di-(l-adamantyl)ethylenediamines has been developed.Thus,diastereomerically pure trans-l-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones 6 and 7 were successfully prepared by optical resolution of((+-))-trans-4,5-dimethoxy-2-imidazolidinone using apocamphanecarbonyl chloride(MAC-Cl)followed by stereospecific and stepwise substitution of the dimethoxyl groups using tert-butyl or 1-adamantyl cuprates to provide(4S,5S)-4,5-di-tert-butyl and(4R,5R)-4,5-di-(l-adamantyl)-2-imidazolidinones 12 and 15,respectively.Furthermore,Af-acetyl 4,5-di-tert-butyl and 4,5-di-(l-adamantyl)-2-imidazolidinones 16a,b were enantioselectively deacetylated using a catalytic oxazaboro-lidine system to provide enantiopure l-p-tolylsulfonyl-4,5-di-tert-butyl-2-imidazolidinones 12 and 19 and l-p-tolylsulfonyl-4,5-di-(l-adamantyl)-2-imidazolidinones 18 and 20,respectively.Finally,N-p-tolylsulfonyl-2-imidazolidinones 12 and 15 were treated with 30 equiv of Ba(OH)_28H_2O to achieve ring cleavage and to provide(15,25)-l,2-di-tert-butylethylenediamine 3 and(lR,2R)-l,2-di-(l-adamantyl)ethylenediamine 4.