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]
Methyl-phenylsulfoximine, a sulfur(VI) compound (left), and S,S-diphenylsulfilimine, a sulfur(IV) compound (right)
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.
In general, aliphatic sulfilimines, unsubstituted at N, are not stable above −30°C (−22°F).[5]
KMnO4 can oxidize sulfilimines to sulfoximines, but the latter are more generally produced from addition of azides to sulfoxides.[5]
Sulfilimine bonds in proteins
Sulfilimine bonds stabilize collagen IV strands found in the extracellular matrix[6] and arose at least 500 mya.[7] 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.
↑ Gilchrist, Thomas L.; Moody, Christopher J. (1977). "The chemistry of sulfilimines". Chemical Reviews. 77 (3): 409–435. doi:10.1021/cr60307a005.
1 2 Roesky, H.W. (1971). "The Sulfur–Nitrogen Bond". In Senning, Alexander (ed.). Sulfur in Organic and Inorganic Chemistry. Vol.1. New York: Marcel Dekker. pp.27–28, 30–31. ISBN0-8247-1615-9. LCCN70-154612– via the Internet Archive.
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