Sulfinamide

Not to be confused with sulfonamide or sulfamide.
General structure of sulfinamides, showing both correct zwitterionic and "expanded octet" simplified convention

In organosulfur chemistry, sulfinamide is a functional group with the structure R−S(O)−NR2 (where R = alkyl or aryl).[1] This functionality is composed of a sulfur-carbon (S−C) single bond, a sulfur-nitrogen (S−N) single bond, and a sulfur-oxygen (S-O) bond (see Sulfoxide for the nature of this bond)[2]. 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 (R−S(O)OH).

Structure

Structure of Davis' sulfinamide (p-tolylsulfinamide), highlighting the pyramidal nature of the S center[3]

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 and more broadly as chiral auxiliaries.

Synthesis

Sulfinamides are traditionally produced by the reaction of sulfinyl chlorides with primary or secondary amines.[1] 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 mesitylsulfinamide.[4][5][6]

Sulfinamides arise in nature by the addition of nitroxyl (HNO) to thiols:[7]

RSH + HNO → RS(O)NH2

References

  1. ^ a b J. G. Tillett (1981). "Sulphinamides". In Saul Patai (ed.). Sulphinic Acids, Esters and Derivatives. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. pp. 185–215. doi:10.1002/9780470772270.ch7. ISBN 978-0-471-91918-6.
  2. ^ Brecher, Jonathan (2008-01-01). "Graphical representation standards for chemical structure diagrams (IUPAC Recommendations 2008)". Pure and Applied Chemistry. 80 (2): 277–410. doi:10.1351/pac200880020277. ISSN 1365-3075.
  3. ^ Eccles, K. S.; Morrison, R. E.; Daly, C. A.; O'Mahony, G. E.; Maguire, A. R.; Lawrence, S. E. (2013). "Co-crystallisation Through Halogen Bonding with Racemic or Enantiopure Sulfinamides". CrystEngComm. 15 (37): 7571–7575. doi:10.1039/C3CE40932E.
  4. ^ Fanelli, D. L.; Szewczyk, J. M.; Zhang, Y.; Reddy, G. V.; Burns, D. M.; Davis, F. A. (2000). "SULFINIMINES (THIOOXIMINE S-OXIDES): ASYMMETRIC SYNTHESIS OF METHYL (R)-(+)-β-PHENYLALANATE FROM (S)-(+)-N-(BENZYLIDENE)-p-TOLUENESULFINAMIDE". Organic Syntheses. 77: 50{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 10, p. 47.
  5. ^ Ruano, J. L.; Alemán, J.; Parra, A.; Cid, M. B. (2007). "PREPARATION OF N-p-TOLYLSULFONYL-(E)-1-PHENYLETHYLIDENEIMINE". Organic Syntheses. 84: 129{{cite journal}}: CS1 maint: multiple names: authors list (link).
  6. ^ Ramachandar, T.; Wu, Y.; Zhang, J.; Franklin A. Davis (2006). "(S)-(+)-2,4,6-TRIMETHYLBENZENESULFINAMIDE". Organic Syntheses. 83: 131{{cite journal}}: CS1 maint: multiple names: authors list (link).
  7. ^ Keceli, Gizem; Toscano, John P. (2014-06-10). "Reactivity of C-Terminal Cysteines with HNO". Biochemistry. 53 (22): 3689–3698. doi:10.1021/bi500360x. ISSN 0006-2960. PMID 24869490.