Sulfimidation of thioether groups - a versatile method for modifying and linking thia/oxa crowns

Reaction of the mixed thioether/ether crowns [9]aneO(2)S 1, [12]aneO(3)S 2 and [18]aneO(4)S(2) 3 with one mol. equivalent of the aminating agent MSH (o-mesitylsulfonylhydroxylamine) in Et2O results in the formation of the mono-sulfimidated systems {[9]aneO(2)(S=NH2)}(+) 1a, {[12]aneO(3)(S=NH2)}(+) 2a and {[18]aneO(4)S(S=NH2)}(+) 3a, while using two mol. equivalents of MSH with 3 gives the disulfimidium cation {[18]aneO(4)(S=NH2)(2)}(2+) 3b. All of these species have been isolated in good yields as the [mesSO(3)](-) (mes = 2,4,6- Me3C6H2) salts and can be readily converted to the [BPh4](-) salts by metathesis with Na[BPh4]. Treatment of 1a or 2a with lithium diisopropylamide (LDA) and N-bromosuccinimide (NBS) at -78 degrees C, followed by addition of a further equivalent of the parent thia/oxa crown, gives monocationic N-bridged sulfi mide bicyclic compounds (4 and 5 respectively), in which the crowns are linked by the sul. midic nitrogen. Reaction of 3a with LDA and NBS leads to formation of the {([18]aneO(4)S(2))N}(+) cation 6 which exhibits an intramolecular S-N-S bridge. Crystallographic studies on representative examples of each compound type are described, together with their spectroscopic properties.