The surprising photochemistry of sultams related to saccharin

Abstract

The known light induced reactions of sulfonamides and sultams are in most (but not all) cases initiated by S–N homolysis. Sulfur dioxide release may be a consequence of this primary process. In the author's laboratory three hitherto unexplored photoreactions of saccharin-derived sultams have been investigated: (i) a novel formal oxygen shift from sulfur to nitrogen generating upto now unknown cyclic N-hydroxysulfinamides; (ii) a condensative dimerization of 2,3-dihydro-1,2- benzoisothiazole 1,1-dioxide generating a new cleft molecule, and (iii) a facile allylic skeletal rearrangement of a pyrrolo-anellated dihydro- 1,2-benzoisothiazole. At least in the latter two cases an initial S–N-homolysis seems to be vital for the processes observed, whereas in the first case some ambiguity remains with respect to the first step. Scope and limitations are discussed and rationales for the conversions observed are presented, with special emphasis on structure proof by X-ray crystal structure determinations. All reactions discussed have to be treated within the wider context of current sulfonamide and sultam photochemistry.

Toward Radiation-Resistant Ionic Liquids. Radiation Stability of Sulfonyl Imide Anions

“…A photoisomerization for saccharin-related sultams and their N-alkyl and N-aryl derivatives that involves the transfer of the oxygen from sulfur to nitrogen, as shown in Scheme 3S, reaction b, in the Supporting Information has also been reported. 32 In the gas phase, this rearrangement (for saccharin, >NH) is endoergic by 1.23 eV, so it can proceed from an excited state; however, our DFT calculations indicate that the corresponding species for the parent anion (>N − ) is not bound, so this isomerization channel is very unlikely. Given the occurrence of SO 2 loss, giving the dimer anion in the mass spectra of irradiated P 666,14 o-benzenedisulfonimide (but not P 666,14 saccharinate, see section 3.5), it seems that a reaction analogous to that shown in Scheme 3S(a) (Supporting Information) may occur in the former IL.…”

“…The resulting diradical can further undergo SO 2 loss. There is a report in the literature, 32 suggesting the occurrence of such SO 2 loss and the subsequent termination of the diradical for N-alkyl saccharin photolyzed in alcohol and benzene (Scheme 3S, reaction a, Supporting Information). A photoisomerization for saccharin-related sultams and their N-alkyl and N-aryl derivatives that involves the transfer of the oxygen from sulfur to nitrogen, as shown in Scheme 3S, reaction b, in the Supporting Information has also been reported.…”

Regioselective Photocycloaddition of Saccharin Anion to π-Systems: Continuous-Flow Synthesis of Benzosultams

“…5, 139.6, 138.5, 136.6, 131.9, 130.8, 129.9, 128.3, 127.0, 126.7, 124.3, 57.6, 47.4, 23.8 6,137.4,134.6,132.6,131.6,129.13,129.05,128.8,128.2,126.3,57.6,45.5. IR (neat, 8, 141.5, 136.8, 135.0, 132.4, 131.7, 129.2, 129.1, 128.8, 128.2, 126.1, 64.1, 53.1, 21. 4,158.5,137.8,134.6,134.1,130.6,129.1,127.4,125.0,120.7,113.8,55.2,52.6,17.8. IR (neat, 8,138.6,137.9,136.4,132.9,132.5,130.9,129.0,128.8,128.1,125.8,68.0,48.5.…”

“…With N-alkylsaccharins, for example, a homolytic N−S bond cleavage with extrusion of SO 2 can be observed. 4 Additionally, the photoaddition of saccharin to α-silylamine by single-electron transfer (SET) pathways was observed. 5 The intramolecular photoreaction of N-[(trimethylsilyl)alkyl]saccharins shows a competitive silyl group transfer, homolysis of the S−N bond, and H-abstraction processes.…”

Exploring the Photophysical and Photochemical Properties of N-(Thioalkyl)-saccharins as an Alternative Route to the Synthesis of Tricyclic Sultams

“…For the case of 3,3-disubstituted 2,3-dihydro-1,2-benzisothiazole 1,1-dioxides, a formal oxygen shift from S to N, generating cyclic N-hydroxysulfinamides, was also observed. 15 Additionally, the intermolecular photoreaction of saccharin with αsilylamine has demonstrated that photoproducts are generated via SET pathways in addition to the homolytic N-S bond cleavage process. 16 More recently, the intramolecular photoreaction of N-[(trimethylsilyl)alkyl]saccharins in solution was studied, showing a competitive silyl group transfer, homolysis of the S−N bond and Habstraction processes, whose relative contribution depends on the reaction conditions.…”