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

Reaction of the mixed thioether/ether crowns [9]aneO2S 1, [12]aneO3S 2 and [18]aneO4S23 with one mol. equivalent of the aminating agent MSH (o-mesitylsulfonylhydroxylamine) in Et2O results in the formation of the mono-sulfimidated systems {[9]aneO2(S[double bond, length as m-dash]NH2)}+1a, {[12]aneO3(S[double bond, length as m-dash]NH2)}+2a and {[18]aneO4S(S[double bond, length as m-dash]NH2)}+3a, while using two mol. equivalents of MSH with 3 gives the disulfimidium cation {[18]aneO4(S[double bond, length as m-dash]NH2)2}2+3b. All of these species have been isolated in good yields as the [mesSO3]− (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 °C, followed by addition of a further equivalent of the parent thia/oxa crown, gives monocationic N-bridged sulfimide bicyclic compounds (4 and 5 respectively), in which the crowns are linked by the sulfimidic nitrogen. Reaction of 3a with LDA and NBS leads to formation of the {([18]aneO4S2)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.