Sulfinamide

Sulfinamide is a functional group in organosulfur chemistry with the structural formula RS(O)NR'2 (where R and R' are organic substituents). This functionality is composed of a sulfur-carbon (S-C) and sulfur-nitrogen (S-N) single bonds, as well as a sulfur-oxygen double bond (S=O), resulting in a tetravalent sulfur centre (in equilibrium with its trivalent zwitterionic form). As a non-bonding electron pair is also present on the sulfur, these compounds are also chiral, and are referred to as S-chiral sulfinamides. Sulfinamides are amides of sulfinic acid (RS(O)OH).

Structure of Davis' sulfinamide (p-tolylsulfinamide), highlighting the pyramidal nature of the S center[1]
Not to be confused with sulfonamide.
General structure of sulfinamides, showing both resonance forms

As sulfinamides do not undergo inversion, their chirality remains conserved and 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. The most commonly sulfinamides for these synthetic applications are tert-butanesulfinamide (Ellman's sulfinamide), p-toluenesulfinamide (Davis' sulfinamide), and 2,4,6-trimethylbenzenesulfinamide.[2][3][4]

Sulfinamides arise in nature by the addition of nitroxyl (HNO) to thiols:[5]

RSH + HNO → RS(O)NH2

References
  1. 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: 7571–7575. doi:10.1039/C3CE40932E.
  2. 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.CS1 maint: multiple names: authors list (link); Collective Volume, 10, p. 47
  3. Ruano, J. L.; Alemán, J.; Parra, A.; Cid, M. B. (2007). "PREPARATION OF N-p-TOLYLSULFONYL-(E)-1-PHENYLETHYLIDENEIMINE". Organic Syntheses. 84: 129.CS1 maint: multiple names: authors list (link)
  4. Ramachandar, T.; Wu, Y.; Zhang, J.; Franklin A. Davis (2006). "(S)-(+)-2,4,6-TRIMETHYLBENZENESULFINAMIDE". Organic Syntheses. 83: 131.CS1 maint: multiple names: authors list (link)
  5. 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.


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