The crystal structures of two isomers of 5-(phenylisothiazolyl)-1,3,4-oxathiazol-2-one

Abstract

The syntheses and crystal structures of two isomers of phenyl isothiazolyl oxathiazolone, C 11 H 6 N 2 O 2 S 2 , are described [systematic names: 5-(3-phenylisothiazol-5-yl)-1,3,4-oxathiazol-2-one, (I), and 5-(3-phenylisothiazol-4-yl)-1,3,4-oxathiazol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å ) molecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetramers linked by strong SÁ Á ÁN [3.072 (2) Å ] and SÁ Á ÁO contacts [3.089 (1) Å ]. The tetramers are -stacked parallel to the a-axis direction. The single molecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central isothiazolyl ring and the pendant oxathiazolone and phenyl rings are 13.27 (6) and 61.18 (7) , respectively], which disrupts the -conjugation between the heteroaromatic isothiazoloyl ring and the non-aromatic oxathiazolone heterocycle. In the crystal of isomer (II), the strong SÁ Á ÁO [3.020 (1) Å ] and SÁ Á ÁC contacts [3.299 (2) Å ] and the non-planar structure of the molecule lead to a form of -stacking not observed in isomer (I) or other oxathiazolone derivatives.

Synthesis and crystal structures of halogenated oxathiazolones and an unexpected propanamide

“…A search of the Cambridge Structural Database (Version 5.42 of September 2021; Groom et al, 2016) revealed that there are 13 crystal structures reported for molecules containing the 1,3,4-oxathiazole heterocycle (Bridson et al, 1994(Bridson et al, , 1995Schriver & Zaworotko, 1995;Vorontsova et al, 1996;McMillan et al, 2006;Krayushkin et al, 2010;Nason et al, 2017;Zhu et al, 2017). The reported structures include three that feature a Csp 2 -Csp 3 bond and eight that have a Csp 2 -Csp 2 bond connecting the substituent to the hetero-…”

“…Cambridge Crystallographic Data Centre (CCDC) software was used to generate a comprehensive list of each bond length within the reported crystal structures of 1,3,4-oxathiazol-2ones with any atom bound to the 5-position (Table 2). The formation of the 1,3,4-oxathiazol-2-one moieties in ( 1) and ( 3) generated structures that are not significantly different from the cumulated averages (Bridson et al, 1994(Bridson et al, , 1995Schriver & Zaworotko, 1995;Vorontsova et al, 1996;McMillan et al, 2006;Krayushkin et al, 2010;Nason et al, 2017;Zhu et al, 2017) for the bond lengths previously reported for related heterocycles [C N 1.271 (5) A ˚, N-S 1.692 (4) A ˚, S-C 1.755 (4) A ˚, C O 1.184 (5) A ˚, O C-O 1.389 (6) A ˚and N C-O 1.374 (5) A ˚]. For comparison purposes, the molecule in the unit cell with the lowest atom labels were selected [a statistical analysis of the structural features of all the crystallographically different molecules in the unit cells of (1) and (2) did not reveal any significant differences] and for compounds (2) and (3), the major components were used for discussion.…”

Synthesis and crystal structure of 3-phenyl-1,4,2-dithiazole-5-thione

“…These differences are consistent with a higher degree of delocalization in the title heterocycle as compared to the oxathiazolone. The current -island structural model for oxathiazolone heterocycles has been suggested to explain the decarboxylation to form the nitrile sulfides (Krayushkin et al, 2010) with longer, weaker endocyclic C-S bonds consistent with lower extrusion temperatures (Zhu et al, 2017).…”