Crystal structures of 4-{(E)-3-[(imino-λ5-azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide and 2-[(imino-λ5-azanylidene)amino]-4-{(E)-3-[(imino-λ5-azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide

The structures of two azide containing imidazole derivatives are reported. The first, C8H12N6O2S, contains one azide group with an Nα—Nβ distance of 1.229 (2) Å and an Nβ—Nγ distance of 1.128 (2) Å. The second, C8H11N9O2S, contains two azide groups with an average Nα—Nβ distance of 1.249 (2) Å and an average Nβ—Nγ distance of 1.132 (2) Å. Each compound contains a bulky protecting group.

The structures of two azide containing imidazole derivatives are reported. Allylic azides are fairly reactive making them attractive starting compounds to convert into amides. The first, C 8 H 12 N 6 O 2 S, contains one azide group with an N -N distance of 1.229 (2) Å and an N -N distance of 1.128 (2) Å . The second, C 8 H 11 N 9 O 2 S, contains two azide groups with an average N -N distance of 1.249 (2) Å and an average N -N distance of 1.132 (2) Å . Each compound contains a bulky protecting group (dimethylaminosulfonyl) which can be easily removed under mildly acidic conditions.

Chemical context
The efficient synthesis of nagelamide alkaloids (a subfamily of oroidin natural products derived from marine sponges) has garnered interest (Du et al., 2006;Das et al., 2016) since first reported (Endo et al., 2004). Allylic azides (Carlson & Topczewski, 2019) are fairly reactive making them attractive starting compounds to convert into amides. Our group has successfully synthesized a number of azide-containing imidazole derivatives and determined their structures. Many of our strategies have led to the successful synthesis of several nagelamide derivatives (Bhandari et al., 2009;Mukherjee et al., 2010). However, the application of our approaches to several other nagelamide congeners were unsuccessful, leading us to rethink our tactics. Recently, we reported the efficient synthesis of amide compounds from allylic azide-containing imidazoles (Herath et al., 2017). In that report we were also able to show that although the imidazoles contained dimethylaminosulfonyl (DMAS) protecting groups, efficient conversion to amides was still possible. In addition, the free imidazole (lacking the protecting group but still containing azide) underwent selective and rapid conversion to amide without the undesired hydrosulfenylation we observed with protected imidazoles. Here we present the crystal structures of two azide-containing imidazoles, 4-{(E)-3-[(imino-5 -azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide (1) and 2- imidazole-1-sulfonamide (2). These compounds were synthesized in the previous study but the structures were not reported. Figs. 1 and 2 show displacement ellipsoid plots of 1 and 2, respectively.
The torsion angles for the azides and dihedral angles between the azides and imidazole rings for both compounds have been measured. The allylic azide torsion angles between 1 and 2 are quite different. The measured torsion angle for the allylic azide (C5-C6-N3-N4) in 1 was À115.21 (13) while the related torsion angle (C5-C6-N6-N7) in 2 was 50.25 (18) . 2 contains one azide group bound to the imidazole at C2 and shows a torsion angle N1-C2-N3-N4 of À174.82 (11) . The allylic azides in both compounds exhibit a similar dihedral angle between the azide and the imidazole ring, 70.3 (11) for 1 and 77.3 (17) for 2. While the imidazolebound azide in 2 shows a dihedral angle of 5.0 (10) . Indeed, the torsion angle and dihedral angle for this particular azide demonstrate the near planarity between the imidazole and its covalently bound azide. Figs. 3 and 4 show the dihedral planes for 1 and 2, respectively.
Both title compounds contain a DMAS protecting group. The amine component of this protecting group is sp 3 -hybridized, as validated by the C-N-C bond angles C6-N6-C8 = 113.86 (10) for 1 and C7-N9-C8 = 113.93 (12) for 2. Both compounds also contain a double bond between C4 and C5. The molecular structure of compound 2, with atom labels and 50% probability displacement ellipsoids for non-H atoms.

Figure 4
Dihedral planes between imidazole and allylic azide for compound 2

Figure 1
The molecular structure of compound 1, with atom labels and 50% probability displacement ellipsoids for non-H atoms.
The imidazole ring in 1 is substituted at the N1 and C3 position with no substitution at C2. The N1-C2 distance is 1.378 (2) Å while the N2-C2 distance is 1.301 (2) Å . However, in 2, the imidazole ring is substituted with an azide group at C2 but this seemingly has no effect on the ring bond distances. The measured bond distances for N1-C2 and N2-C2 in 2 are 1.385 (2) and 1.310 (2) Å , respectively.
There is, however, a significant difference in the measured N1-S1 distance for the two compounds. The imidazole ring is substituted at the N1 position for both compounds with DMAS. The N1-S1 distance for 1 is 1.686 (1) Å and 1.718 (1) Å for 2. The disparity may be attributed to the presence of azide, which is substituted at the C2 position for 2.
Although both compounds contain aromatic rings, there appears to be no -stacking present in the crystals of either compound. The stacking appears more staggered, most likely due to the presence of bulky DMAS groups on both compounds. However, the staggering in 1 appears more pronounced than in 2. In other words, the molecules are further apart in 1. This is most likely due to the larger torsion angle for the azide in 1 than in 2.

Database survey
A search of related compounds was conducted in the Cambridge Structural Database (Version 5.38; Groom et al., 2016). One very closely related compound, methyl 3-(1-(dimethylsulfamoyl)-1H-imidazol-5-yl)acrylate, was reported . This particular compound contains an imidazole with a DMAS protecting group and an allylic ester moiety. The DMAS amine has a C-N-C angle of 114.33 (14) , showing the same amine hybridization exhibited in 1 and 2. The C4 C5 double bond distance is measured to be 1.330 (2) Å which is similar to the bond distances in 1 and 2 [1.333 (2) and 1.340 (2) Å respectively].
The crystal structure of a related allylic azide has been reported from our previous study (Herath et al., 2017). This particular compound is a dimerized molecule with two allylic azides.

Figure 5
Close contacts for compound 1.

Figure 6
Close contacts for compound 2.
dissolving title compounds in ethanol with heating and slowly cooling in a freezer. Crystals appeared after about 1 week.

Refinement
Crystal data, data collection and structure refinement details for 1 and 2 are summarized in Table 3. Refinement for both compounds were routine. H atoms were positioned geometrically (C-H = 0.95-0.98 Å ) and allowed to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for methyl H and 1.2U eq (C) for other H atoms.

4-{(E)-3-[(Imino-λ 5 -azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide (compound_1)
Crystal data  (6) 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.

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.