title: β-amino esters from the reductive ring opening of aziridine-2-carboxylates.
abstract: A general study is undertaken to examine the scope of the reductive ring opening of aziridine-2-carboxylates with samarium diiodide. The competition between C-C and C-N bond cleavage is examined as a function of the nature of the N-substituent of the aziridine, the nature of the substituent in the 3-position of the aziridine, and whether the substituent in the 3-position is in a cis or trans relationship with the carboxylate in the 2-position. The desired C-N bond cleavage leads to β-amino esters that are the predominant products for most aziridines with an N-activating group. However, C-C cleavage products are observed with an aryl group in the 3-position; this can be particularly pronounced with cis-aziridines where a nearly equal mixture of the two is observed. Exclusive formation of the C-N cleavage product is observed for all aziridines with the strongly N-activating p-toluene sulfonate group. Similarly high selectivity is observed for the 2-trimethylsilylethyl sulfonate group (SES), which is easier to remove. The utility of these methods is illustrated in the synthesis of protected forms of (R)-β(3)-DOPA and L-DOPA from the same aziridine, the former by SmI2-mediated reductive opening at C-2 and the latter by palladium-mediated reductive opening at C-3.
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zhao
authors.forename: Zhenjie
authors.initials: Z
authors.lastname: Lu
authors.forename: William D
authors.initials: WD
authors.lastname: Wulff
mesh_terms: D001388:Aziridines / Q000737:chemistry*; D001557:Benzenesulfonates / Q000737:chemistry; D004952:Esters; D010165:Palladium / Q000737:chemistry; D013237:Stereoisomerism; D014297:Trimethylsilyl Compounds / Q000737:chemistry
chemical_list: C000596034:2-trimethylsilylethyl sulfonate; D001388:Aziridines; D001557:Benzenesulfonates; D004952:Esters; D014297:Trimethylsilyl Compounds; C073440:aziridine-2-carboxylic acid; D010165:Palladium; C029501:4-toluenesulfonic acid