Sulfinamide
{{Short description|1=Molecules of the form >N–S(=O)–}}
{{distinguish|sulfonamide|sulfamide|sulfinylamine}}
File:Sulfinamide_structure.png
In organosulfur chemistry, sulfinamide is a functional group with the structure {{chem2|R\sS(O)\sNR2}} (where R = alkyl or aryl).{{cite book|author=J. G. Tillett|chapter=Sulphinamides|year=1981|editor=Saul Patai|title=Sulphinic Acids, Esters and Derivatives|doi=10.1002/9780470772270.ch7|publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups|pages=185–215 |isbn=978-0-471-91918-6 }} This functionality is composed of a sulfur-carbon ({{chem2|S\sC}}) single bond, a sulfur-nitrogen ({{chem2|S\sN}}) single bond, and a sulfur-oxygen (S-O) bond (see Sulfoxide for the nature of this bond).{{Cite journal |last=Brecher |first=Jonathan |date=2008-01-01 |title=Graphical representation standards for chemical structure diagrams (IUPAC Recommendations 2008) |url=https://www.degruyter.com/document/doi/10.1351/pac200880020277/html |journal=Pure and Applied Chemistry |language=en |volume=80 |issue=2 |pages=277–410 |doi=10.1351/pac200880020277 |issn=1365-3075}} As a non-bonding electron pair is present on the sulfur, the sulfur atom is a stable stereogenic centre, and so these compounds are chiral. They are sometimes referred to as S-chiral sulfinamides. Sulfinamides are amides of sulfinic acid ({{chem2|R\sS(O)OH}}).
Structure
Sulfinamides do not undergo inversion. They can therefore be synthesised and/or isolated in enantiopure forms. This has led to their use as chiral ammonia equivalents. Chiral sulfinamides such as tert-butanesulfinamide, p-toluenesulfinamide{{cite journal |doi= 10.15227/orgsyn.077.0050|title= Sulfimines (Thiooximine S-Oxides): Asymmetric Synthesis of Methyl (R)-(+)-β-Phenylalanate from (S)-(+)-N-(Benzylidine)-p-Toluenesulfimade|journal= Organic Syntheses|date= 2000|volume= 77|page= 50|author=Dean L. Fanelli, Joanna M. Szewczyk, Yulian Zhang, G. Venkat Reddy, David M. Burns, Franklin A. Davis}}{{cite journal |doi= 10.15227/orgsyn.084.0129|title= Preparation of N-p-Tolylsulfonyl-(E)-1-Phenylethyleideneimine|journal= Organic Syntheses|date= 2007|volume= 84|page= 129|author=José Luis García Ruano, José Alemán, Alejandro Parra, M. Belén Cid}} and 2,4,6-trimethylbenzenesulfinamide{{cite journal |doi= 10.15227/orgsyn.083.0131|title= (S)-(+)-2,4,6-Trimethylbenzenesulfinamide|journal= Organic Syntheses|date= 2006|volume= 83|page= 131}} are all chiral auxiliaries.
Synthesis
Sulfinamides are traditionally produced by the reaction of sulfinyl chlorides with primary or secondary amines. They also arise by the addition of Grignard reagents to sulfinylamines, followed by protonation:
:RMgX + R'N=S=O → RS(O)(NR'MgX)
:RS(O)(NR'MgX) + H2O → RS(O)(NR'H) + "MgX(OH)"
Yet another route entails peracid-oxidation of sulfenylphthalimides, which gives sulfinylphthalimides.
Examples
A common sulfinamide is tert-butanesulfinamide (Ellman's sulfinamide), p-toluenesulfinamide (Davis' sulfinamide), and mesityl
Sulfinamides arise in nature by the addition of nitroxyl (HNO) to thiols:{{Cite journal|last1=Keceli|first1=Gizem|last2=Toscano|first2=John P.|date=2014-06-10|title=Reactivity of C-Terminal Cysteines with HNO|url=https://pubs.acs.org/doi/10.1021/bi500360x|journal=Biochemistry|language=en|volume=53|issue=22|pages=3689–3698|doi=10.1021/bi500360x|pmid=24869490|issn=0006-2960|url-access=subscription}}
:RSH + HNO → RS(O)NH2