Class of chemical compounds containing an S=N bond
In
chemistry, a sulfilimine (or sulfimide) is a type of
chemical compound containing a
sulfur-to-
nitrogen bond which is often represented as a
double bond (S=N). In fact, a double bond violates the
octet rule, and the bond may be considered a
single bond with a
formal charge of +1 on the sulfur and a formal charge of −1 on the nitrogen. The
parent compound is sulfilimine H2S=NH, which is mainly of theoretical interest.
Examples include S,S-diphenylsulfilimine[2] and sulfoximines [
Category] such as methylphenylsulfoximine:[3] In the case of a sulfoximine, the bonds can be considered single bonds, with formal charges of −1 on both the oxygen and the nitrogen, and a formal charge of +2 on the sulfur.
Preparation
Most sulfilimines are N-substituted with electron-withdrawing groups. These compounds are typically prepared by oxidation of thioethers with electrophilic amine reagents, such as
chloramine-T in the presence of a base:[4]
R2S + ClNHTs → R2S=NTs + HCl
An alternative route involves reactions of electrophilic sulfur compounds with amines. The imidosulfonium reagents provide a source of "Me2S2+", which are attacked by amines.
Sulfilimine bonds in proteins
Sulfilimine bonds stabilize
collagen IV strands found in the
extracellular matrix[5] and arose at least 500 mya.[6] These bonds covalently connect
hydroxylysine and
methionine residues of adjacent polypeptide strands to form a larger collagen trimer.
References
^Elsegood, Mark R. J.; Holmes, Kathryn E.; Kelly, Paul F.; Parr, Jonathan; Stonehouse, Julia M. (2002). "The preparation and structure of novel sulfimide systems; X-ray crystal structures of 1,4-(PHS{NH})2C6H4 (And dihydrate), 1,2-(PHS{NH})(PHS)C6H4·H2O and of [Ph2SNH] and its hydrate". New Journal of Chemistry. 26 (2): 202–206.
doi:
10.1039/b103502a.