Crystal structures and Hirshfeld surfaces of two 1,3-benzoxathiol-2-one derivatives

Abstract

The crystal structures of 6-methoxy-1,3-benzoxathiol-2-one, C 9 H 8 O 3 S, (I), and 2-oxo-1,3-benzoxathiol-6-yl acetate, C 9 H 6 O 4 S, (II), are described. Compound (I) is almost planar (r.m.s. deviation for the non-H atoms = 0.011 Å ), whereas (II) shows a substantial twist between the fused-ring system and the acetate substituent [dihedral angle = 74.42 (3) ]. For both structures, the bond distances in the heterocyclic ring suggest that little if any conjugation occurs. In the crystal of (I), C-HÁ Á ÁO hydrogen bonds link the molecules into [111] chains incorporating alternating R 2 2 (8) and R 2 2 (12) inversion dimers. The extended structure of (II) features C(7) [201] chains linked by C-HÁ Á ÁO hydrogen bonds, with further C-HÁ Á ÁO bonds and weak -stacking interactions connecting the chains into a three-dimensional network. Hirshfeld fingerprint analyses for (I) and (II) are presented and discussed. Chemical context1,3-Benzoxathiol-2-one and its derivatives have various biological properties including antibacterial, antimycotic, antioxidant, antitumor and anti-inflammatory activities (Vellasco Jú nior et al., 2011;Chazin et al., 2015). They also act as inhibitors of carbonic anhydrase II (Barrese et al., 2008) and monoamine oxidase (Mostert et al., 2016). The first synthesized 1,3-benzoxathiol-2-one, 6-hydroxy-1,3-benzoxathiol-2-one C 7 H 4 O 3 S, also known as tioxolone or thioxolone, has been used for many years in the treatment of acne and other skin diseases (e.g. psoriasis) (Berg & Fiedler, 1959).A recent study reported the syntheses and antifungal activities of some derivatives of tioxolone (Terra et al., 2018). In the present article we report the crystal structures and Hirshfeld surface analyses of two compounds with different substituents at the 6-position of the ring system obtained in that study, viz. 6-methoxy-1,3-benzoxathiol-2-one, C 9 H 8 O 3 S, (I), and 2-oxo-1,3-benzoxathiol-6-yl acetate, C 9 H 8 O 3 S, (II).. ISSN 2056-9890 Structural commentaryCompound (I) crystallizes in space group P1 with one molecule in the asymmetric unit (Fig. 1), which is almost planar (r.m.s. deviation for the non-hydrogen atoms = 0.011 Å ): the ethoxy side chain adopts an extended conformation [C6-O3-C8-C9 = 179.82 (12) ]. Within the oxathiol-2-one ring system, the C1-O1, C1 O2 and C1-S1 bond lengths are 1.3732 (18), 1.1905 (19) and 1.7766 (16)Å , respectively, and the O1-C1-S1 and C1-S1-C3 bond angles are 111.07 (11) and 90.62 (7) , respectively. These distance data suggest that there is little if any conjugation (i.e. partial double-bond character) involving the C1-O1 and C1-S1 bonds with the C1 O2 group.A single molecule of compound (II) makes up the asymmetric unit in space group P2 1 /c (Fig. 2). The ring system is almost planar (r.m.s. deviation for C1-C7/O1/S1 = 0.032 Å ) but there is a substantial twist about the C6-O3 bond, as indicated by the dihedral angle between the ring system and the acetate group of 74.42 (3) . Key geometrical data for the heterocyclic ring are C1-O1 = 1.3864 (15), C1 ...

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