Synthesis and crystal structure of 2-chloro-1-(3-hydroxyphenyl)ethanone

The synthesis, crystal structure, and some spectroscopic details for 2-chloro-1-(3-hydroxyphenyl) ethanone, C8H7O2Cl, an α-haloketone of use in organic synthesis, are described.

The structure of 2-chloro-1-(3-hydroxyphenyl)ethanone, C 8 H 7 ClO 2 , an -haloketone is described. The molecule is planar (r.m.s. deviation = 0.0164 Å ) and in the crystal, inversion-symmetric dimers are formed as a result of pairs of strong O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds. A brief comparison is made with structurally related compounds deposited in the CSD. In addition, the synthesis and some spectroscopic details are presented.

Chemical context
-Haloketones have proven to be useful building blocks for the preparation of compounds of various classes because of their high reactivity and selective transformations with a variety of reagents (Erian et al., 2003). Chlorinated acetophenones are widely used in organic synthesis as intermediates for the manufacture of active pharmaceutical ingredients (Ott-Dombrowski et al., 2019). For example, 2-chloro-1-(4-hydroxyphenyl)ethanone is a reagent that is used in the preparation of hydroxypyrimidine derivatives for their HDAC (histone deacetylase) inhibitory activity (Kemp et al., 2011). In light of the importance of -haloketones, this paper reports the synthesis, crystal structure, and some spectroscopic details for the title compound, C 8 H 7 O 2 Cl, (I).

Structural commentary
The molecule of I ( Fig. 1) is planar (r.m.s. deviation = 0.0164 Å ), with the largest deviation being for Cl1, which is 0.0346 (5) Å from the mean plane through all non-H atoms due to the O2-C7-C8-Cl1 torsion angle of À2.07 (14) . The hydroxyl hydrogen atom, H1O, which was refined freely, lies 0.045 (16) Å out of the mean plane, with a C2-C3-O1-H1O torsion angle of 1.8 (12) , its position being mandated by intermolecular hydrogen bonding (see section 3, Supramolecular details). All bond lengths and angles fall within the expected ranges for organic structures.

Figure 2
A partial packing plot showing the main supramolecular motif in I: a hydrogen-bonded dimer between inversion-related [symmetry code: (i) Àx + 1, Ày + 1,   An ellipsoid plot (50% probability) of I. Hydrogen atoms are drawn as small circles.
MEXCOJ (Ambekar et al., 2013) has OC OPh in place of the OH in I. Other similar structures in the literature include: LEFNAN (Fun et al., 2012), which is the 4-hydroxyphenyl analogue of I and crystallizes with the symmetry of P2 1 /c; FUHHOG (Qing & Zhang, 2009), which is the bromo analogue of LEFNAN; and CUYDOR (Mei et al., 2015), which has 4-fluorophenyl in place of the halogen of LEFNAN and FUHHOG.

Synthesis, crystallization and spectroscopic details
Synthesis and crystallization: For the synthesis of I, sulfuryl chloride (150 mg, 1.1 mmol) was added dropwise to a stirred mixture of 3-hydroxyacetophenone (100 mg, 0.74 mmol) in 5 ml of methanol and 10 ml of ethyl acetate/dichloromethane at 293-303 K. After completion of the addition, it was allowed to return to RT with stirring for 1 h. The reaction was monitored by TLC. Then the solvent was removed under reduced pressure by rotary evaporation to give the desired product in 95% yield. An overall reaction scheme is depicted in Fig. 4. X-ray quality crystals were obtained by crystallization from ethanol (m.p. 352-354 K). Spectroscopic data: Infrared and NMR spectroscopic details are as follows.

Refinement
Crystal data, data collection, and structure refinement details are given in Table 2. All hydrogen atoms were found in difference-Fourier maps, but subsequently, the carbon-bound hydrogens were included using riding models, with constrained distances set to 0.95 Å (Csp 2 -H) and 0.99 Å (R 2 CH 2 ). The hydroxyl hydrogen atom coordinates were refined freely. In all cases, U iso (H) values were set to 1.2U eq of the attached atom.

Figure 4
The overall reaction scheme for the synthesis of I.

Computing details
Data collection: APEX3 (Bruker, 2016); cell refinement: APEX3 (Bruker, 2016); data reduction: APEX3 (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2019/2 (Sheldrick, 2015b); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELX (Sheldrick, 2008) and publCIF (Westrip, 2010). 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.