Selective Ring-Opening of Nonactivated Amino Aziridines by Thiols and Unusual Nucleophilic Substitution of a Dibenzylamino Group

Abstract

The reaction of chiral 2-(1-aminoalkyl)aziridines with different thiols, in the presence of BF3‚Et2O, is reported. The obtained products were dependent on the structure of the starting aminoaziridines. Thus, enantiopure (2S,3S)-2-(alkylthio)alkane-1,3-diamines were obtained fromaziridines with C-2 substituents with lower steric congestion and partially racemized (2S,3S)-2,3-bis(alkylthio)alkan-1-amines3(ee)56-66%) from aziridines with larger C-2 subtituents. In both cases, the opening of the nonactivated aziridine ring at C-2 took place with retention of configuration and proceeded with regio- and stereoselectivity at C-2. In the synthesis of 3, 2 equiv of thiol reacts with and the opening of aziridine ring at C-2 was followed by an unusual displacement of the dibenzyl amino group by a second equivalent of thiol. The regio-chemistry and relative configuration of compounds was established by single-crystal X-ray analysis. A mechanism is proposed to explain the results obtained