6,7-Diphenyl-5-thia-7-aza-spiro-[2.6]nonan-8-one 5,5-dioxide.

The racemic mixture of the title compound, C19H19NO3S, crystallizes in space group P with two homochiral mol-ecules in each asymmetric unit. The seven-membered ring in both mol-ecules is in a pucker-chair conformation. The extended structure exhibits C-H⋯O hydrogen bonds, of which two connect crystallographically independent mol-ecules to generate a chain propagating along the b-axis direction. One C-H grouping of the cyclo-propyl ring is in close contact with the phenyl ring of the neighboring independent mol-ecule in C-H⋯π type inter-actions with carbon atom-ring-centroid distances of 3.544 (5) and 3.596 (4) Å. Other inter-actions are of the parallel-reciprocal type, with the chiral carbon atom of one mol-ecule donating a proton to an oxygen atom of the sulfone group of a symmetry-related mol-ecule and vice-versa. Symmetry-related mol-ecular pairs also exhibit T-type inter-actions between aromatic rings with inter-planar angles of 74.2 (2) and 69.2 (2)° and inter-centroid distances of 4.965 (4) and 5.114 (4) Å.

Crystal structures of the sulfones of 2,3-diphenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one and 2,3-diphenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one.

The title sulfones, 2,3-diphenyl-2,3-di-hydro-4H-1,3-benzo-thia-zine-1,1,4-trione, C20H15NO3S, and 2,3-diphenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zine-1,1,4-trione, C19H14N2O3S, crystallize in space group P21/n with two mol-ecules in each of the asymmetric units and have almost identical unit cells and extended structures. In both structures, the thia-zine rings exhibit a screw-boat pucker. The inter-molecular inter-actions observed are C-H⋯O-type hydrogen bonds and parallel partial π-π stacking between the fused aromatic rings (benzo- or pyrido-) of the core of the mol-ecules within each asymmetric unit, and also connecting to mol-ecules with translational periodicity in the a-axis direction in what can be described as columns (two per asymmetric unit) of stacked mol-ecules with alternating chirality. The pendant phenyl groups of both mol-ecules do not participate in aromatic ring inter-actions.

Crystal structures of rac-2,3-diphenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zine-1,1,4-trione and N-[(2S,5R)-1,1,4-trioxo-2,3-diphenyl-1,3-thia-zinan-5-yl]acet-amide.

The syntheses and crystal structures of two thia-zinone compounds, namely, rac-2,3-diphenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zine-1,1,4-trione, C16H15NO3S, in its racemic form, and N-[(2S,5R)-1,1,4-trioxo-2,3-diphenyl-1,3-thia-zinan-5-yl]acet-amide, C18H18N2O4S, in an enanti-opure form, are reported. The thia-zine rings in the two structures differ in their puckering, as a half-chair in the first and a boat pucker in the second. The extended structures for both compounds have only C-H⋯O-type inter-actions between symmetry-related mol-ecules, and exhibit no π-π stacking inter-actions in spite of each having two phenyl rings.

Synthesis and crystal structure of racemic (R*,R*)-2,2'-(1,4-phenyl-ene)bis-(3-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one).

In the racemic title compound, C26H24N2O2S2, one of the thia-zine rings shows a twisted boat conformation (Q = 0.743 Å, θ = 92.1°) and the other a half-chair puckering (Q = 0.669 Å, θ = 54.3°). The terminal phenyl rings are almost parallel to each other [dihedral angle 21.71 (10)°]. Both of these rings are orthogonal to the central phenyl ring, subtending a dihedral angle of about 78° in each case. The extended structure is consolidated by C-H⋯O and C-H⋯S hydrogen bonds as well as aromatic ring inter-actions of parallel-displaced and T-type. The mol-ecule has approximate C2 local symmetry but this is not carried over to its three-dimensional structure or the inter-molecular inter-actions.

T3P-Promoted Synthesis of a Series of 2-Aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones and Their Activity against the Kinetoplastid Parasite Trypanosoma brucei.

A series of fourteen 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-phenyl-C-aryl imines with thionicotinic acid, two difficult substrates. The reactions were operationally simple, did not require specialized equipment or anhydrous solvents, could be performed as either two or three component reactions, and gave moderate-good yields as high as 63%. This provides ready access to N-phenyl compounds in this family, which have been generally difficult to prepare. As part of the study, the first crystal structure of neutral thionicotinic acid is also reported, and showed the molecule to be in the form of the thione tautomer. Additionally, the synthesized compounds were tested against T. brucei, the causative agent of Human African Sleeping Sickness. Screening at 50 µM concentration showed that five of the compounds strongly inhibited growth and killed parasites.

2,3-Diphenyl-2,3-dihydro-4H-1,3-thiaza-4-one heterocycles inhibit growth and block completion of cytokinesis in kinetoplastid parasites.

Kinetoplastid parasites are model eukaryotes with a complex cell cycle that is highly regulated both spatially and temporally. In addition, diseases caused by these parasites continue to have a significant impact on human and animal health worldwide. While there have been advancements in chemotherapy for these diseases, there is a continual need for an arsenal of compounds that have robust anti-parasite activity with minimal impact on the human host. While investigating a series of 2,3-diphenyl-2,3-dihydro-4H-1,3-thiaza-4-one heterocycles with potential activity against these parasites, we found a pyridothiazinone that inhibits growth of the monoxenous parasite Crithidia fasciculata and two life cycle stages of Trypanosoma brucei. This inhibition is more pronounced in T. brucei and is associated with an unusual pre-abscission cell cycle arrest. Exploring the mode of action for these and related compounds in kinetoplastids may provide tools with which to explore cell cycle regulation in these important organisms.

Crystal structures of two solvated 2-aryl-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-ones.

The synthesis and crystal structures of 2-(4-fluoro-phen-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one toluene hemisolvate (1), C19H13FN2OS·0.5C7H8, and 2-(4-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-pyrido[3,2-e][1,3]thia-zin-4-one iso-propanol 0.25-solvate 0.0625-hydrate (2), C19H13N3O3S·0.25C3H7O·0.0625H2O, are reported. Both are racemic mixtures (centrosymmetric crystal structures) of the individual com-pounds and incorporate solvent mol-ecules in their structures. Compound 2 has four thia-zine mol-ecules in the asymmetric unit. All the thia-zine rings in this study show an envelope pucker, with the C atom bearing the substituted phenyl ring displaced from the other atoms. The phenyl and aryl rings in each of the mol-ecules are roughly orthogonal to each other, with dihedral angles of about 75°. The extended structures of 1 and 2 are consolidated by C-H⋯O and C-H⋯N(π), as well as T-type (C-H⋯π) inter-actions. Parallel aromatic ring inter-actions (π-π stacking) are observed only in 2.

Crystal structures of two isomeric 2-aryl-3-phenyl-1,3-thia-zepan-4-ones.

The crystal of 6-(3-nitro-phen-yl)-7-phenyl-5-thia-7-aza-spiro-[2.6]nonan-8-one (1), C19H18N2O3S, has monoclinic (P21/n) symmetry while that of its isomer 6-(4-nitro-phen-yl)-7-phenyl-5-thia-7-aza-spiro-[2.6]nonan-8-one (2), has ortho-rhom-bic (Pca21) symmetry: compound 1 has two mol-ecules, A and B, in the asymmetric unit while 2 has one. In all three mol-ecules, the seven-membered thia-zepan ring exhibits a chair conformation with Q2 and Q3 values (Å) of 0.521 (3), 0.735 (3) and 0.485 (3), 0.749 (3) in 1 and 0.517 (5), 0.699 (5) in 2. In each structure, the phenyl rings attached to adjacent atoms of the thia-zepan ring have inter-planar angles ranging between 41 and 47°. Except for the nitro groups, the three mol-ecules have similar conformations when overlayed in pairs. Both crystal structures are consolidated by C-H⋯O hydrogen bonds.

Crystal structures of two 1,3-thia-zolidin-4-one derivatives featuring sulfide and sulfone functional groups.

The crystal structures of two closely related compounds, 1-cyclo-hexyl-2-(2-nitro-phen-yl)-1,3-thia-zolidin-4-one, C15H18N2O3S, (1) and 1-cyclo-hexyl-2-(2-nitro-phen-yl)-1,3-thia-zolidin-4-one 1,1-dioxide, C15H18N2O5S, (2), are presented. These compounds are comprised of three types of rings: thia-zolidinone, nitrophenyl and cyclo-hexyl. In both structures, the rings are close to mutually perpendicular, with inter-planar dihedral angles greater than 80° in each case. The thia-zol-idinone rings in both structures exhibit envelope puckering with the S atom as flap and the cyclo-hexyl rings are in their expected chair conformations. The two structures superpose fairly well, except for the orientation of the nitro groups with respect to their host phenyl ring, with a difference of about 10° between 1 and 2. The extended structure of 1 has two kinds of weak C-H⋯O inter-actions, giving rise to a closed ring formation involving three symmetry-related mol-ecules. Structure 2 has four C-H⋯O inter-actions, two of which are exclusively between symmetry-related thia-zolidinone dioxide moieties and have a parallel 'give-and-take-fashion' counterpart. In the other two inter-actions, the nitrophenyl ring and the cyclo-hexane ring each offer an H atom to the two O atoms on the sulfone group. Additionally, a C-H⋯π inter-action between a C-H group of the cyclo-hexane ring and the nitrophenyl ring of an adjacent mol-ecule helps to consolidate the structure.

Crystal structure of meso-3,3'-(1,4-phenyl-ene)bis-(2-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one).

The crystal structure of the title compound - meso-C26H24N2O2S2 with two stereocenters - has half the mol-ecule in the asymmetric unit with the other half generated by a crystallographic center of inversion. The thia-zine ring is in a conformation that is between half-chair and envelope [θ = 52.51 (17)°]. The phenyl ring on the 2-carbon atom of the thia-zine ring is pseudo-axial. The central phenyl ring of the mol-ecule is close to orthogonal to the phenyl rings on either side with an angle of 76.85 (11)° between those planes. In the crystal, pairwise, weak C-H⋯O hydrogen bonds between the central phenyl ring and the oxygen atoms of neighboring mol-ecules result in continuous strips propagating along the a-axis direction. Hydro-phobic inter-actions of the C-H⋯π type are also observed.

Crystal structures of two 2,3-diaryl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-ones.

The syntheses and crystal structures of 2,3-bis-[3-(tri-fluoro-meth-yl)phen-yl]-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one (di-m-CF3; C22H13F6NOS) (1) and 2,3-bis-(4-methyl-phen-yl)-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one (di-p-CH3; C22H19NOS) (2) are reported. Each structure is racemic: the asymmetric unit of 2 consists of two mol-ecules. In both 1 and 2, the six-membered 1,3-thia-zine ring is close to an envelope conformation with the chiral C atom forming the flap. In 1, the 2-aryl group is pseudo-equatorial, while in 2 it is pseudo-axial. In 1, the pendant aryl rings form a V shape with an inter-centroid distance of 3.938 (3) Šand an acute dihedral angle of 48.3 (2)° between them. Both CF3 groups are disordered over two orientations in 0.687 (19):0.313 (19) and 0.667 (16):0.33 (16) ratios. In each of the independent mol-ecules of 2, the aryl rings are almost orthogonal to each other [dihedral angles = 85.50 (12) and 86.07 (11)°]. In both structures, the chiral C atom and the O atoms participate in C-H⋯O-type hydrogen bonding between symmetry-related mol-ecules of 1 or the independent enanti-omers in 2, forming chains along the c-axis direction in 1 and the b-axis direction in 2. Additionally, in 1, π-π contacts of both face-to-face and edge-to-face type, as well as π-H⋯O and π-H⋯F inter-actions are observed. In 2, a racemic mixture of mol-ecules forms layers in the ac plane linked by weak π-π and C-H⋯π inter-actions.

Spontaneous resolution and crystal structure of (2S)-2-(3-nitro-phen-yl)-3-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one; crystal structure of rac-2-(4-nitro-phen-yl)-3-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one.

The crystal structures of isomeric rac-2-(4-nitro-phen-yl)-3-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one (C16H14N2O3S) (1) and (2S)-2-(3-nitro-phen-yl)-3-phenyl-2,3,5,6-tetra-hydro-4H-1,3-thia-zin-4-one (C16H14N2O3S) (2) are reported here. While 1 crystallizes in a centrosymmetric space group, the crystal of 2 chosen for data collection has mol-ecules only with (2S) chirality. This is the result of spontaneous resolution during crystallization, as the synthesis produces a racemic mixture. A crystal with (2R) mol-ecules was also found in the same crystallization vial (structure factors available). The six-membered thia-zine ring in both 1 and 2 displays an envelope conformation with the S atom forming the flap. The aryl rings in both structures adopt an approximate V shape with angles between their planes of 46.97 (14)° in 1 and 58.37 (10)° in 2. In both structures, the mol-ecules form layers in the ab plane. Within such a layer in 1, one of the O atoms of the nitro-phenyl group accepts a C-H⋯O hydrogen bond from the CH group at position 5 of the thia-zine ring of a mol-ecule of opposite chirality, forming chains along the a-axis direction. Each of the thia-zine rings also participate in C-H⋯O bonds with the same carbon atom as above, resulting in chains along the b-axis direction, albeit of monochiral type. Adjacent layers are consolidated along the c-axis direction by pairs of parallel hydrogen bonds (C-H⋯O type) between the nitro-phenyl groups of enanti-omers. In 2, the two C-H⋯O hydrogen bonds contribute to chain formation along the b-axis direction. Weak edge-to-face inter-actions between the aryl groups of neighbouring mol-ecules in 1, and C-H⋯π inter-actions between a thia-zine ring CH group and a phenyl group of a neighboring mol-ecule in 2 are also observed.

Crystal structure of (1S,2S,5R)-5-acetyl-amino-4-oxo-2,3-diphenyl-1,3-thia-zinan-1-ium-1-olate.

The asymmetric unit of the enanti-omerically pure title compound, C18H18N2O3S, comprises two independent mol-ecules (A and B) having almost identical conformations. When overlayed, the alignment-r.m.s. deviation value is 0.30 Å. The six-membered heterocycle has a twisted half-chair conformation in both mol-ecules. The O atom on the S atom of the ring is pseudo-axial on the thia-zine ring and trans to both a phenyl group substituent and the acetamide group in each case. The two benzene rings in each mol-ecule are almost orthogonal to each other, with inter-planar dihedral angles of 83.79 (17) and 86.95 (16)°. The acetamide group is pseudo-equatorial and a phenyl ring is pseudo-axial on the thia-zine ring. Both mol-ecules show a weak intra-molecular C-H⋯O inter-action between H-atom donors of one of the phenyl rings and the acetamide group. In the crystal, an inter-molecular N-H⋯O(thia-zine) hydrogen bond links B mol-ecules along the 21 (b) screw axis and, in addition, an N-H⋯O(acetamide) hydrogen bond links A and B mol-ecules across a. A two-dimensional layered structure lying parallel to (001) is generated, also involving weak inter-molecular C-H⋯O inter-actions.

Crystal structure of 2,3-diphenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one 1-oxide.

In the racemic title compound, C20H15NO2S, the planes of the two phenyl substituents form dihedral angles of 48.97 (15) and 69.26 (15)° with that of the fused benzene ring of the parent benzo-thia-zine ring, while the heterocyclic thia-zine ring exhibits a screw-boat pucker. The O atom on the S atom of the ring is pseudo-axial on the thia-zine ring and trans to the 2-phenyl group. In the crystal, mol-ecules are arranged in layers in the ac plane, the layers being linked across b through inter-molecular C-H⋯O hydrogen-bonding inter-actions.

Crystal structure of rac-2,3-diphenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one 1-oxide.

In the title compound, C16H15NO2S [alternative name: rac-2,3-diphenyl-1,3-thia-zinan-4-one 1-oxide], the thia-zine ring exhibits an envelope conformation, with the S atom forming the flap. The sulfoxide O atom is in a pseudo-axial position on the thia-zine ring and is trans to the phenyl group on C-2. The phenyl rings form a dihedral angle of 89.47 (19)°. In this racemate crystal, homochiral mol-ecules form slabs parallel to (010) of thickness b/2 which then stack with alternating chirality in the b-axis direction. The stacking is aided by edge-to-face inter-actions between the phenyl rings of racemic mol-ecules. Within each of the single-enanti-omer slabs, the mol-ecules are held by C-H⋯O-type inter-actions, with an H⋯O distance of 2.30 Å, forming infinite chains along the c-axis direction, as well by the edge-to-face inter-actions between phenyl rings of neighboring mol-ecules in the a-axis direction.

Crystal structures of three substituted 3-aryl-2-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-ones.

Three ring-substituted 3-aryl analogs of 2-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one, namely 3-(4-meth-oxy-phen-yl)-2-phenyl-4H-1,3-benzo-thia-zin-4-one, C21H17NO2S, (I), 2-phenyl-3-[4-(tri-fluoro-meth-yl)phen-yl]-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one toluene hemisolvate, C21H14F3NOS·0.5C7H8, (II), and 3-(3-bromo-phen-yl)-2-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one toluene hemisolvate, C20H14BrNOS·0.5C7H8, (III), were synthesized and their crystal structures determined. The hemisolvates differ in that in (II), the asymmetric unit comprises two molecules of the benzo-thia-zinone compound and a toluene solvent mol-ecule, whereas in (III), the unit comprises one benzo-thia-zinone mol-ecule and a half-occupancy toluene solvent mol-ecule. All crystals are of racemic mixtures of the chiral 2-C atom of the thia-zine moiety, which in all structures has a screw-boat puckering, with the puckering amplitude values within the range 0.575-0.603 Å. In all three structures, the benzene plane of the benzo-thia-zine system makes a dihedral angle in the range 78.60 (5) to 98.40 (5)° with the unsubstituted benzene plane and in the range 70.50 (1) to 121.00 (5)° with the substituted benzene plane. The CF3 substituent group in one of the mol-ecules of (II) shows positional disorder, with an occupancy ratio of 0.57 (3):0.43 (3). In the crystals of (I) and (II), weak inter-molecular C-H⋯O inter-actions are present, giving in (I), mol-ecules arranged in a plane parallel to (010), and in (II), chains along a. In addition, all three structures show weak C-H⋯π inter-actions involving various aromatic rings.

Crystal structure of the 1:1 adduct of 2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one with tri-phenyl-tin chloride.

The title adduct, chlorido-(2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one-κO)tri-phenyl-tin, [Sn(C6H5)3Cl(C16H15NOS)], resulted from reaction of 2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one with tri-phenyl-tin chloride. The thia-zine ring has an envelope conformation with the S atom forming the flap. The mol-ecule has five phenyl rings, two of them attached to the thia-zine ring at positions 2 and 3, and three in coordination with the Sn(IV) atom. The three rings of the tri-phenyl-tin group are involved in intra-molecular inter-actions of different types, C-H⋯O, edge-to-face (or T-type) π-π inter-actions with the 3-phenyl ring of the thia-zine, T-type inter-actions with both phenyl rings of the thia-zine etc. On the other hand, all the phenyl rings participate in inter-molecular π-π inter-actions. There is one instance of a 'parallel-displaced'-type inter-action extending continuously along the a-axis direction and seven instances of T-type inter-actions stabilizing the crystal lattice.

Crystal structures of 2-(4-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one and 2-(2-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one.

The crystal structures are reported of the isomeric compounds 2-(4-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one, (I), and 2-(2-nitro-phen-yl)-3-phenyl-2,3-di-hydro-4H-1,3-benzo-thia-zin-4-one, (II), both C20H14N2O3S, being the para-nitro and ortho-nitro forms, respectively, the meta-form of which is known [Yennawar et al. (2013). Acta Cryst. E69, o1679]. The six-membered thia-zone ring fused with a benzene ring displays a screw-boat conformation with a total puckering amplitude of 0.627 (1) Šin (I), and a near screw-boat conformation with a total puckering amplitude of 0.600 (1) Šin (II). The dihedral angles between the planes of the substituent nitrophenyl and phenyl and rings with the benzene ring of the parent benzo-thia-zone moiety are 75.93 (5) and 82.61 (5)° [in (I)], and 76.79 (6) and 71.66 (6)° [in (II)]. Weak inter-molecular C-H⋯O hydrogen-bonding inter-actions between aromatic H-atom donors and both a nitro-O atom and a thia-zone O-atom acceptor in (I) and a thia-zone O atom in (II) are present, forming in (I) a centrosymmetric 22-membered cyclic dimer which is extended through a similar inversion-related 14-membered cyclic hydrogen-bonding association into a zigzag chain structure extending along c. In (II), a single inter-molecular C-H⋯O hydrogen bond gives a chain structure extending along b. In addition, weak C-H⋯π inter-actions are present in both structures [minimum C⋯ring-centroid separations = 3.630 (2) and 3.581 (2) Å, respectively].

Crystal structures of 2,3-bis-(4-chloro-phen-yl)-1,3-thia-zolidin-4-one and trans-2,3-bis-(4-chloro-phen-yl)-1,3-thia-zolidin-4-one 1-oxide.

In the crystal structures of the title compounds, C15H11Cl2NOS, (1), and C15H11Cl2NO2S, (2), wherein (2) is the oxidized form of (1), the thia-zolidine ring is attached to two chloro-phenyl rings. The chloro-phenyl ring on the 2-carbon atom position points in the same direction as that of the S atom in (1), while in (2), the S atom points in the opposite direction. The O atom on the chiral S atom in (2) is trans to the chloro-phenyl ring on the 2-carbon. The chloro-phenyl ring planes in each structure are close to orthogonal, making dihedral angles of 78.61 (6) and 87.46 (8)° in (1) and (2), respectively. The thia-zolidine ring has a twisted conformation on the S-Cmethine bond in (1), and an envelope conformation with the S atom 0.715 (3) Šout of the plane of other four atoms in (2). In the crystal of (1), mol-ecules are linked by C-H⋯O hydrogen bonds, as well as by slipped parallel π-π inter-actions [inter-centroid distance = 3.840 (3) Å] between inversion-related phenyl rings, forming sheets parallel to (001). In the crystal of (2), mol-ecules are linked via C-H⋯O and C-H⋯Cl hydrogen bonds, forming slabs parallel to (001).

Crystal structure of N-[(2S,5R)-4-oxo-2,3-diphenyl-1,3-thia-zinan-5-yl]acetamide 0.375-hydrate.

The asymmetric unit of the title compound, C18H18N2O2S.0.375H2O, has two independent organic mol-ecules (A and B) and 3/4 of a water mol-ecule distributed over three sites. In mol-ecule A, the 1,3-thia-zine ring is in a boat conformation, with the C atoms at the 2- and 5-positions out of the plane. The angle between the two phenyl rings is 51.70 (12)°. In mol-ecule B, the thia-zine ring is in a half-chair conformation, with the S atom forming the back of the half-chair. The angle between the two phenyl rings is 84.44 (14)°. The A mol-ecule features an intra-molecular N-H⋯O hydrogen bond, which closes an S(5) ring motif. In the crystal, the corresponding N-H grouping of the B mol-ecule participates in an inter-molecular hydrogen bond to the A mol-ecule. The A mol-ecule participates in a C-H⋯O inter-action back to the B mol-ecule, whilst the B mol-ecule features an intra-molecular C-H⋯O link, which generates an S(10) loop.