Synthesis and crystal structure of rac-2-(1,3-dioxoisoindolin-2-yl)ethyl 4-methyl-N-phenyl-N′-(triisopropylsilyl)benzenesulfondiimidoate: the first member of a new substance class

The synthesis and crystal structure of rac-2-[7-methyl-4-(4-methylphenyl)-4-(phenylimino)-6,6-bis(propan-2-yl)-3-oxa-4λ6-thia-5-aza-6-silaoct-4-en-1-yl]-2,3-dihydro-1H-isoindole-1,3-dione are reported.

The different aza-analogs of sulfonamides and sulfones have interesting properties for medicinal chemistry due to the (additional) nitrogen atom(s). Besides the potential centrochirality of sulfur, the nitrogen substituents offer new possibilities for functionalization optimizing steric demand, solubility and reactivity.
The herein reported sulfondiimidoate 1 is, based on extensive database searches, not yet described in the literature and therefore represents the first member of a new substance class. It can be described as an aza-oxo-inverse sulfonamide or an aza-analogue of a sulfonimidoate.

Structural commentary
The title compound 1 crystallizes in the triclinic crystal system and P1 as the centrosymmetric space group, having one molecule in the asymmetric unit (Fig. 1). Geometric parameters may be regarded as normal. A selection is listed in Table 1.

Database survey
The  (Groom et al., 2016), all of which are sulfonimidamides.
Restricting this query to a single bond (instead of any bond) between the sulfur and the oxygen returns zero hits. The mean distance between sulfur and oxygen in the 85 hits dataset is 1.436 with a standard deviation of 0.014. The distance S1-O1 (see also Table 1) is hence clearly a single bond and similar functional groups have not been missed by setting the query in too narrow a way.

Synthesis and crystallization
Molecular schemes with the atom numbering used in the NMR assignments can be found in Figures S1-S3 in the supporting information. Solvent residue signals were used as internal standard according to the literature [ 1 H-NMR: (CHCl 3 ) = 7.26 ppm; 13 C-NMR: (CDCl 3 ) = 77.16 ppm; (Gottlieb et al., 1997)]. The synthesis is shown in Fig. 3.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. Hydrogen atoms were refined isotropically using a riding model. The C-H bond distances were constrained to 0.95 Å for aromatic C-H moieties, and to 1.00, 0.99 and 0.98 Å for aliphatic C-H, CH 2 and CH 3 moieties, respectively. Methyl-H atoms were allowed to rotate but not to tip to best fit the experimental electron density. U iso (H) values were set to a multiple of U eq (C) with 1.5 for CH 3 , and 1.2 for C-H, CH 2 groups, respectively.

Funding information
Funding for this research was provided by: Merck KGaA.
Acta Cryst. (2022). E78 research communications  -2-(1,3-dioxoisoindolin-2-yl)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.56 e Å −3 Δρ min = −0.38 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.