sulfilimine
{{Short description|1=Class of chemical compounds containing an S=N bond}}
File:Diphenylsulfimide-from-xtal-2002-3D-balls.png of the diphenylsulfimide molecule, {{chem2|Ph2S\dNH}}{{cite journal | doi = 10.1039/b103502a| title = 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| date = 2002| last1 = Elsegood| first1 = Mark R. J.| last2 = Holmes| first2 = Kathryn E.| last3 = Kelly| first3 = Paul F.| last4 = Parr| first4 = Jonathan| last5 = Stonehouse| first5 = Julia M.| journal = New Journal of Chemistry| volume = 26| issue = 2| pages = 202–206}}]]
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 ({{chem2|S\dN}}). 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 {{chem2|H2S\dNH}}, which is mainly of theoretical interest.
Examples include S,S-diphenylsulfilimine{{cite web | url = https://www.sigmaaldrich.com/catalog/product/aldrich/232173 | title = S,S-Diphenylsulfilimine | publisher = Sigma-Aldrich }} and sulfoximines {{bracket|Category}} such as methylphenylsulfoximine:{{cite web | url = https://www.sigmaaldrich.com/catalog/product/aldrich/68916 | title = (R)-(−)-S-Methyl-S-phenylsulfoximine | publisher = Sigma-Aldrich }} File:Sulfilimines.svg
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:{{cite journal | doi = 10.1021/cr60307a005| title = The chemistry of sulfilimines| date = 1977| last1 = Gilchrist| first1 = Thomas L.| last2 = Moody| first2 = Christopher J.| journal = Chemical Reviews| volume = 77| issue = 3| pages = 409–435}}
:{{chem2 | R2S + ClNHTs → R2S\dNTs + HCl }}
An alternative route involves reactions of electrophilic sulfur compounds with amines. The imidosulfonium reagents provide a source of "{{chem2|Me2S(2+)}}", which are attacked by amines.
In general, aliphatic sulfilimines are not stable above {{cvt|-30|C}}.{{cite book|title=Sulfur in Organic and Inorganic Chemistry|volume=1|editor-first=Alexander|editor-last=Senning|year=1971|publisher=Marcel Dekker|location=New York|lccn=70-154612|isbn=0-8247-1615-9|first=H. W.|last=Roesky|chapter=The Sulfur–Nitrogen Bond|pages=27-28,30-31}}
KMnO4 can oxidize sulfilimines to sulfoximines, but the latter are more generally produced from addition of azides to sulfoxides.
Sulfilimine bonds in proteins
Sulfilimine bonds stabilize collagen IV strands found in the extracellular matrix{{cite journal| journal=Science |title=A sulfilimine bond identified in collagen IV. |volume=325 |issue=5945 |pages=1230–1234 |date=September 4, 2009 |vauthors=Vanacore R, Ham AL, Voehler M, Sanders CR, Conrads TP, Veenstra TD, Sharpless KB, Dawson PE, Hudson BG |pmid=19729652| pmc=2876822 |url=|doi=10.1126/science.1176811|bibcode= 2009Sci...325.1230V}} and arose at least 500 mya.{{cite journal | doi = 10.1073/pnas.1318499111 | title = A unique covalent bond in basement membrane is a primordial innovation for tissue evolution | date = 2014 | last1 = Fidler | first1 = Aaron L. | last2 = Vanacore | first2 = Roberto M. | last3 = Chetyrkin | first3 = Sergei V. | last4 = Pedchenko | first4 = Vadim K. | last5 = Bhave | first5 = Gautam | last6 = Yin | first6 = Viravuth P. | last7 = Stothers | first7 = Cody L. | last8 = Rose | first8 = Kristie Lindsey | last9 = McDonald | first9 = W. Hayes | last10 = Clark | first10 = Travis A. | last11 = Borza | first11 = Dorin-Bogdan | last12 = Steele | first12 = Robert E. | last13 = Ivy | first13 = Michael T. | last14 = Hudson | first14 = Julie K. | last15 = Hudson | first15 = Billy G. | last16 = Hudson | first16 = Billy G. | journal = Proceedings of the National Academy of Sciences | volume = 111 | issue = 1 | pages = 331–336 | doi-access = free | pmid = 24344311 | pmc = 3890831 | bibcode = 2014PNAS..111..331F }} These bonds covalently connect hydroxylysine and methionine residues of adjacent polypeptide strands to form a larger collagen trimer.