Inverted regioselectivity of C-H amination: Unexpected oxidation at beta- rather than gamma-C-H.

A rare example of beta- over gamma-C-H selectivity during Rh-catalysed sulfamate ester cyclisation is presented; from derivatives of 1,6-anhydro-beta-d-mannopyranose, five-membered sulfamidates were formed in preference to the typical six-membered oxathiazinane intramolecular insertion products. A 3D structure of sulfamate 1 helps to rationalise this unusual selectivity and analyses suggest that n-->sigma*(CH) interactions may be a key controlling factor.