Intramolecular asymmetric amidations of sulfonamides and sulfamates catalyzed by chiral dirhodium(II) complexes

Enantioselective intramolecular amidation of aliphatic sulfonamides was achieved for the first time by means of chiral carboxylatodirhodium(II) catalysts in conjunction with PhI(OAc)(2) and MgO in high yields and with enantioselectivities of up to 66% (Scheme 3, Table 1). The best results were obtained with [Rh-2{(S)-nttl)(4)] and [Rh-2{(R)-ntv)(4)] as catalysts ((S)-nttl=(alphaS)-alpha-(tert-butyl)-1,3-dioxo-2H-benz[de]isoquinoline-2-acetato, (R)-nto=(alphaR)-alpha-isopropyl-1,3-dioxo-2H-benz[de] isoquinoline-2-acetato). In addition, these carboxylatodirhodium(II) catalysts were also efficient in intramolecular amidations of aliphatic sulfamates esters, although the enantioselectivity of these latter reactions was significantly lower (Scheme 4, Table 3).