research communications
Synthesis and characterization of 3-methyl-6-[(propynyloxy)methyl]-1,4-dioxane-2,5-dione
aFaculty of Pharmacy, Université de Montréal, 2900 Edouard-Montpetit Blvd, Montreal, Quebec, H3T1J4, Canada, and bDepartment of Chemistry, Université de Montréal, 2900 Edouard-Montpetit Blvd, Montreal, Quebec, H3T1J4, Canada
*Correspondence e-mail: patrice.hildgen@umontreal.ca
The number of known asymmetrically substituted hemilactides, important precursors for obtaining regular derivatives of polylactide polymers, is still limited and structural characterization of most of them is incomplete. In the title racemic 1,4-dioxane-2,5-dione derivative, C9H10O5, the hemilactide heterocycle exhibits a twist-boat conformation. The bulkier propynyloxymethyl group is in an axial position with a gauche conformation for the CH2–O–CH2–C segment. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds, forming inversion dimers. The dimers are linked by further C—H⋯O contacts, forming a three-dimensional structure.
Keywords: crystal structure; 3-methyl-6-propynyloxymethyl-1,4-dioxane-2,5-dione; lactide; synthesis.
CCDC reference: 1555000
1. Chemical context
Cyclic dilactides, or hemilactides, close structural analogs of 1,4-dioxane-2,5-dione (glycolide) with methyl- or methylene-containing substituents at the sp3 C atoms, are the most important precursors for obtaining polylactide polymers, which are widely employed in biodegradable plastics and in the food and biomedical industries due to their intrinsic biocompatibility and biodegradability (Gerhardt et al., 2006). Well-tuned architectures of substituted hemilactides lead to the creation of new polylactide materials with regular structures that allow clarification of polymer behaviour at the supramolecular level, as well as achieving new useful properties (Fuoco et al., 2016; Trimaille et al., 2007; Zhang & Song, 2014). Nevertheless, the further development of the field is hampered by the fact that asymmetrically substituted hemilactides still constitute a very limited group of compounds, the structural characterization of most of which remains incomplete. In this context, the goal of the present study was to elaborate a reliable protocol for obtaining 3-methyl-6-[(propynyloxy)methyl]-1,4-dioxane-2,5-dione, 1.
2. Structural commentary
The molecule of the final product (Fig. 1) possesses a 1,4-dioxane-2,5-dione six-membered ring, as well as the two different substituents, i.e. methyl and propynyloxymethyl groups, linked to atoms C1 and C3, respectively, determining the aimed architecture of 1. In general, the bond lengths and angles are in normal ranges for organic The hemilactide heterocycle exhibits a twisted boat conformation, where atoms C1, C2 and O1 are in one plane and atoms C1, C3, C4 and O2 are in another plane; the planes are inclined at a dihedral angle of 27.9 (2)°. The values of the observed puckering parameters [θ = 84.8 (3)° and φ = 308.2 (3)°] deviate slightly from those corresponding to an ideal boat conformation (θ = 90° and φ = 300°). Two stereocentres represented by the C1 and C3 atoms have opposite i.e. R,S (and S,R in the centrosymmetric counterpart), the substituents at which adopt a trans configuration with respect to the ring, by minimizing repulsive interactions. The bulkier propynyloxymethyl group is located above the ring, i.e. in the axial position with a gauche conformation for the C6—O5—C7—C8 segment, at a dihedral angle of 71.3 (2)°. A similar conformation has been observed in meso-3,6-dipropargyloxymethyl-1,4-dioxane-2,5-dione (Zhang et al., 2015).
3. Supramolecular features
In the crystal cell of 1 (Fig. 2), all the 1,4-dioxane-2,5-dione rings are located in parallel planes at a distance of approximately 2.0 Å, but do not tend to form molecular stacks and organize the rings neither into columns, as reported for hemilactides bearing relatively small substituents, such as 3,6-dimethyl-1,4-dioxane-2,5-dione (van Hummel et al., 1982) and 3-bromo-3,6-dimethyl-1,4-dioxane-2,5-dione and 3-methylene-6-methyl-1,4-dioxane-2,5-dione (Fiore et al., 2010), nor into supramolecular formations where one half of the parallel plane is perpendicular to the other, as reported in the cases of 3-benzyloxymethyl-6-methyl-1,4-dioxane-2,5-dione (Kooijman et al., 2005) and 3,6-diphenyl-l,4-dioxane-2,5-dione (Lynch et al., 1990). In addition, the crystal packing shows some short C—H⋯O contacts (Table 1) leading to the pairwise molecular binding, i.e. by hydrogen bonds. It is assumed that the packing is mostly determined by the contact involving the acid acetylenyl H9 and ketone O4 atoms (Fig. 2), analogous to the centrosymmetric interactions reported for symmetric meso-3,6-dipropargyloxymethyl-1,4-dioxane-2,5-dione (Zhang et al., 2015). It is worthy of note that the contains no residual solvent-accessible voids.
4. Database survey
A search in the Cambridge Structural Database (Version 5.38 with two updates; Groom et al., 2016) for pure and functionalized (i.e. glycolides with one methyl substituent) returned 25 entries, including different lactide (Kooijman et al., 2014; Fedushkin et al., 2009; van Hummel et al., 1982) and other derivatives (Zhang et al., 2015; Fiore et al., 2010; Kooijman et al., 2005; Bolte et al.,1994; Lynch et al., 1990).
5. Synthesis and crystallization
The desired product 1 was obtained from the initial rac-1-chloropropane-2,3-diol (2) via a three-step pathway (see Fig. 3) inspired partly by general protocols (Bredikhina et al., 2014; Trimaille et al., 2004; Nagase et al., 2008), comprising the oxidation of 2 to rac-3-chloro-2-hydroxypropanoic acid (3) followed by the etherification with propargyl alcohol to 2-hydroxy-1-(propynyloxymethyl)propanoic acid (4) and the final double esterification of 4 with bromopropyonyl bromide. The final purification of 1 was performed by auto-flash-chromatography on silica, using chloroform as to give, after evaporation under reduced pressure, a white crystalline solid (see supporting information for more details on the synthesis and structural characterization of the intermediate and final products).
6. Refinement
Crystal data, data collection and structure . H atoms were located from Fourier difference maps and fully refined.
details are summarized in Table 2
|
Supporting information
CCDC reference: 1555000
https://doi.org/10.1107/S2056989017008581/ff2148sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017008581/ff2148Isup2.hkl
Details related to the synthesis, purification and characterization techniques used in the study. DOI: https://doi.org/10.1107/S2056989017008581/ff2148sup3.pdf
Supporting information file. DOI: https://doi.org/10.1107/S2056989017008581/ff2148Isup4.cml
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008).C9H10O5 | F(000) = 416 |
Mr = 198.17 | Dx = 1.425 Mg m−3 |
Monoclinic, P21/c | Ga Kα radiation, λ = 1.34139 Å |
a = 6.9774 (5) Å | Cell parameters from 9932 reflections |
b = 6.8273 (5) Å | θ = 4.0–60.8° |
c = 19.4895 (14) Å | µ = 0.65 mm−1 |
β = 95.804 (3)° | T = 100 K |
V = 923.66 (12) Å3 | Chunk, clear light colourless |
Z = 4 | 0.11 × 0.08 × 0.08 mm |
Bruker Venture Metaljet diffractometer | 2055 independent reflections |
Radiation source: Metal Jet, Gallium Liquid Metal Jet Source | 1640 reflections with I > 2σ(I) |
Helios MX Mirror Optics monochromator | Rint = 0.073 |
Detector resolution: 10.24 pixels mm-1 | θmax = 60.9°, θmin = 4.0° |
ω and φ scans | h = −9→9 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −8→8 |
Tmin = 0.570, Tmax = 0.752 | l = −25→25 |
19524 measured reflections |
Refinement on F2 | Hydrogen site location: difference Fourier map |
Least-squares matrix: full | All H-atom parameters refined |
R[F2 > 2σ(F2)] = 0.063 | w = 1/[σ2(Fo2) + (0.1166P)2 + 0.2436P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.183 | (Δ/σ)max < 0.001 |
S = 1.05 | Δρmax = 0.35 e Å−3 |
2055 reflections | Δρmin = −0.37 e Å−3 |
168 parameters | Extinction correction: SHELXL2016 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0045 (17) |
Experimental. X-ray crystallographic data for I were collected from a single crystal sample, which was mounted on a loop fiber. Data were collected using a Bruker Venture diffractometer equipped with a Photon 100 CMOS Detector, a Helios MX optics and a Kappa goniometer. The crystal-to-detector distance was 4.0 cm, and the data collection was carried out in 1024 x 1024 pixel mode. |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.8442 (2) | 0.6986 (2) | 0.38601 (7) | 0.0450 (4) | |
O2 | 0.8604 (2) | 0.3277 (2) | 0.44578 (7) | 0.0445 (4) | |
O3 | 1.0103 (2) | 0.5925 (2) | 0.30315 (8) | 0.0528 (5) | |
O4 | 0.7313 (2) | 0.4446 (2) | 0.53563 (7) | 0.0500 (4) | |
O5 | 0.5693 (2) | 0.3519 (2) | 0.32715 (7) | 0.0433 (4) | |
C1 | 0.8967 (3) | 0.3454 (3) | 0.37415 (10) | 0.0442 (5) | |
H1 | 1.029 (4) | 0.277 (3) | 0.3718 (12) | 0.047 (6)* | |
C2 | 0.9217 (3) | 0.5552 (3) | 0.35135 (10) | 0.0427 (5) | |
C3 | 0.7092 (3) | 0.6521 (3) | 0.43558 (10) | 0.0413 (5) | |
H3 | 0.591 (3) | 0.624 (3) | 0.4123 (11) | 0.033 (5)* | |
C4 | 0.7669 (3) | 0.4688 (3) | 0.47711 (10) | 0.0412 (5) | |
C5 | 0.6982 (4) | 0.8289 (4) | 0.48109 (12) | 0.0490 (6) | |
H5A | 0.817 (4) | 0.861 (4) | 0.5017 (13) | 0.050 (6)* | |
H5B | 0.656 (4) | 0.940 (4) | 0.4515 (14) | 0.059 (7)* | |
H5C | 0.613 (4) | 0.797 (4) | 0.5153 (16) | 0.061 (8)* | |
C6 | 0.7425 (3) | 0.2424 (3) | 0.32707 (12) | 0.0452 (5) | |
H6A | 0.725 (3) | 0.111 (4) | 0.3442 (12) | 0.041 (6)* | |
H6B | 0.783 (3) | 0.234 (3) | 0.2801 (14) | 0.047 (6)* | |
C7 | 0.4081 (3) | 0.2573 (3) | 0.28966 (11) | 0.0472 (5) | |
H7A | 0.299 (3) | 0.349 (3) | 0.2863 (11) | 0.041 (6)* | |
H7B | 0.440 (3) | 0.222 (3) | 0.2426 (14) | 0.047 (6)* | |
C8 | 0.3455 (3) | 0.0836 (3) | 0.32598 (10) | 0.0437 (5) | |
C9 | 0.2952 (3) | −0.0550 (3) | 0.35607 (12) | 0.0476 (5) | |
H9 | 0.252 (4) | −0.157 (4) | 0.3776 (15) | 0.060 (8)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0527 (9) | 0.0485 (8) | 0.0346 (8) | −0.0021 (6) | 0.0088 (6) | 0.0033 (6) |
O2 | 0.0478 (8) | 0.0505 (8) | 0.0355 (8) | 0.0025 (6) | 0.0065 (6) | 0.0062 (6) |
O3 | 0.0586 (9) | 0.0640 (10) | 0.0373 (8) | −0.0117 (7) | 0.0125 (7) | −0.0011 (7) |
O4 | 0.0548 (9) | 0.0617 (9) | 0.0338 (8) | −0.0022 (7) | 0.0066 (6) | 0.0060 (6) |
O5 | 0.0446 (8) | 0.0472 (8) | 0.0383 (8) | −0.0030 (6) | 0.0057 (6) | −0.0039 (6) |
C1 | 0.0453 (11) | 0.0522 (12) | 0.0367 (11) | 0.0023 (9) | 0.0119 (9) | 0.0025 (8) |
C2 | 0.0436 (11) | 0.0538 (12) | 0.0310 (10) | −0.0062 (9) | 0.0050 (8) | 0.0003 (8) |
C3 | 0.0411 (10) | 0.0519 (11) | 0.0311 (9) | 0.0003 (9) | 0.0048 (8) | 0.0023 (8) |
C4 | 0.0392 (10) | 0.0520 (11) | 0.0321 (10) | −0.0041 (8) | 0.0028 (8) | 0.0017 (8) |
C5 | 0.0534 (13) | 0.0552 (13) | 0.0380 (11) | 0.0041 (10) | 0.0035 (10) | −0.0019 (9) |
C6 | 0.0521 (12) | 0.0463 (11) | 0.0390 (11) | 0.0015 (9) | 0.0128 (9) | −0.0016 (8) |
C7 | 0.0511 (12) | 0.0557 (12) | 0.0344 (10) | −0.0038 (10) | 0.0026 (9) | −0.0012 (9) |
C8 | 0.0445 (11) | 0.0535 (12) | 0.0327 (10) | −0.0027 (9) | 0.0019 (8) | −0.0055 (8) |
C9 | 0.0503 (12) | 0.0507 (12) | 0.0419 (11) | −0.0062 (10) | 0.0049 (9) | −0.0031 (9) |
O1—C2 | 1.335 (3) | C3—C4 | 1.522 (3) |
O1—C3 | 1.451 (2) | C3—C5 | 1.505 (3) |
O2—C1 | 1.449 (3) | C5—H5A | 0.91 (3) |
O2—C4 | 1.344 (3) | C5—H5B | 0.98 (3) |
O3—C2 | 1.203 (3) | C5—H5C | 0.96 (3) |
O4—C4 | 1.203 (3) | C6—H6A | 0.97 (2) |
O5—C6 | 1.421 (3) | C6—H6B | 0.99 (3) |
O5—C7 | 1.432 (3) | C7—H7A | 0.98 (2) |
C1—H1 | 1.04 (2) | C7—H7B | 1.00 (3) |
C1—C2 | 1.515 (3) | C7—C8 | 1.470 (3) |
C1—C6 | 1.515 (3) | C8—C9 | 1.184 (3) |
C3—H3 | 0.92 (2) | C9—H9 | 0.88 (3) |
C2—O1—C3 | 119.98 (16) | C3—C5—H5A | 110.8 (16) |
C4—O2—C1 | 121.22 (16) | C3—C5—H5B | 107.6 (15) |
C6—O5—C7 | 112.74 (16) | C3—C5—H5C | 107.4 (16) |
O2—C1—H1 | 104.3 (14) | H5A—C5—H5B | 106 (2) |
O2—C1—C2 | 113.46 (17) | H5A—C5—H5C | 110 (2) |
O2—C1—C6 | 111.23 (18) | H5B—C5—H5C | 115 (2) |
C2—C1—H1 | 106.6 (13) | O5—C6—C1 | 107.90 (17) |
C6—C1—H1 | 110.0 (13) | O5—C6—H6A | 110.3 (13) |
C6—C1—C2 | 110.91 (17) | O5—C6—H6B | 111.0 (14) |
O1—C2—C1 | 118.72 (18) | C1—C6—H6A | 109.2 (13) |
O3—C2—O1 | 120.44 (19) | C1—C6—H6B | 109.7 (14) |
O3—C2—C1 | 120.83 (19) | H6A—C6—H6B | 108.8 (19) |
O1—C3—H3 | 109.1 (13) | O5—C7—H7A | 108.0 (13) |
O1—C3—C4 | 112.30 (16) | O5—C7—H7B | 109.8 (14) |
O1—C3—C5 | 106.96 (18) | O5—C7—C8 | 112.01 (17) |
C4—C3—H3 | 105.6 (13) | H7A—C7—H7B | 109.8 (18) |
C5—C3—H3 | 111.0 (13) | C8—C7—H7A | 106.4 (13) |
C5—C3—C4 | 111.88 (17) | C8—C7—H7B | 110.8 (13) |
O2—C4—C3 | 117.51 (17) | C9—C8—C7 | 179.1 (2) |
O4—C4—O2 | 119.26 (18) | C8—C9—H9 | 177.3 (19) |
O4—C4—C3 | 123.22 (19) | ||
O1—C3—C4—O2 | −31.7 (2) | C3—O1—C2—O3 | 168.81 (18) |
O1—C3—C4—O4 | 149.05 (19) | C3—O1—C2—C1 | −11.5 (3) |
O2—C1—C2—O1 | −23.6 (3) | C4—O2—C1—C2 | 30.6 (3) |
O2—C1—C2—O3 | 156.06 (19) | C4—O2—C1—C6 | −95.2 (2) |
O2—C1—C6—O5 | 70.2 (2) | C5—C3—C4—O2 | −152.00 (19) |
C1—O2—C4—O4 | 176.43 (18) | C5—C3—C4—O4 | 28.8 (3) |
C1—O2—C4—C3 | −2.8 (3) | C6—O5—C7—C8 | 71.3 (2) |
C2—O1—C3—C4 | 39.0 (2) | C6—C1—C2—O1 | 102.4 (2) |
C2—O1—C3—C5 | 162.14 (17) | C6—C1—C2—O3 | −77.9 (2) |
C2—C1—C6—O5 | −57.0 (2) | C7—O5—C6—C1 | −174.10 (17) |
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O4i | 0.92 (2) | 2.60 (2) | 3.247 (3) | 127.8 (16) |
C3—H3···O5 | 0.92 (2) | 2.49 (2) | 3.033 (2) | 118.1 (16) |
C6—H6B···O3ii | 0.99 (3) | 2.47 (2) | 3.369 (3) | 151.0 (19) |
C7—H7A···O3iii | 0.98 (2) | 2.66 (2) | 3.627 (3) | 169.1 (18) |
C9—H9···O4iv | 0.88 (3) | 2.58 (3) | 3.412 (3) | 156 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, y−1/2, −z+1/2; (iii) x−1, y, z; (iv) −x+1, −y, −z+1. |
Acknowledgements
F. Belanger-Gariepy, M. Cibian and A. Melkoumov are gratefully acknowledged for their help with the elemental and
and the auto-flash-chromatography purification, respectively.Funding information
Funding for this research was provided by: Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de recherche du Québec – Nature et technologies (FRQNT).
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