Lithiated Dithiane Ring Opening of N-Protected Aziridines

Significance

Reported is the ring opening of aziridines with lithiated 1,3-dithiane and its derivatives to afford 1,3-dithiane-protected β-amino ­carbonyl products. In the case of 1,3-dithiane-2-carboxylic acid, the products proved too polar to isolate and therefore were cyclized to give 3-protected pyrrolidine-2,3-diones. Enantiopurity was retained where aziridines with a defined stereocenter were used. One example of removal of each protecting group was shown. In the case of the N-Bus product, the 1,3-dithiane required removal prior to deprotection due to its instability ­towards triflic acid. The N-SES product was converted into the corresponding N-carbamate as it is known that N-acylation facilitates SES removal.