Synthesis and Crystal Structures of Two New Oxaspirocyclic Compounds

Two new oxaspirocyclic compounds, 8-(4-(dimethylamino)benzylidene)-6,10-dioxaspiro[4.5] decane-7,9-dione (1) and 8-(4-hydroxybenzylidene)-6,10-dioxaspiro[4.5]decane-7,9-dione (2) have been synthesized and their structures determined by single crystal X-ray crystallography. Compound 1, C17H19NO4, belongs to the monoclinic system, space group P21/c with a = 6.2554(13) Å, b = 14.605(3) Å, c = 16.265(3) Å, β = 95.97(3)◦, V = 1477.9(5) Å3, Z = 4, Dc = 1.354 g/cm3, F(000) = 640, μ(MoKa) = 0.097 mm−1, the final R = 0.0570 and wR = 0.1667. Compound 2, C15H14O5, is also of the monoclinic system, space group P21/c with a = 10.739(2) Å, b = 18.348(4) Å, c = 6.7799(14) Å, β = 104.20(3)◦, V = 1295.1(5) Å3, Z = 4, Dc = 1.407 g/cm3, F(000) = 608, μ(MoKa) = 0.106 mm−1, the final R = 0.0568 and wR = 0.1739. Some C–H···O intraand intermolecular hydrogen bonds and π··· π stacking interactions are both observed in the two lattice structures. The difference between them is that one type of C–H···π supramolecular interaction (1) and one type of O–H···O intermolecular hydrogen bond (2) are observed.

The two compounds both consist of a phenyl ring and 6,10-dioxaspiro [4.5]decane-7,9-dione group which connects a five-membered cyclopentane ring with the other O-containing six-membered ring by a C spiro atom (Figure 1).The selected bond lengths and bond angles of compound 1 are similar to those of 2 correspondingly.

IR Spectra
The IR spectra of the two compounds show a little difference.The broad absorptions at 3265 cm −1 for 2 are assigned to the O-H stretching vibration of PhOH.The strong bands at 1705 cm −1 1 and 1745 cm −1 2, respectively, are due to the C=O stretching vibration of the 1,3-dioxane ring.The broad absorptions at 1167 cm −1 , 1126 cm −1 for 1 and at 1204 cm −1 , 1163 cm −1 for 2 are assigned to the C-O stretching vibration of the 1,3-dioxane ring.Meanwhile, a similar band at 1609 cm −1 and 1688 cm −1 was observed in the IR spectra of 1 and 2, respectively, indicting C=C stretching vibration of N(CH 3 ) 2 −ph−C=C in 1 and HO−ph−C=C in 2. The IR spectra of the two compounds are in agreement with the structural data.

Materials and Methods
All the reagents and solvents from commercial sources were used without further purification.The IR spectra were recorded as KBr pellets with a Nicolet FT-IR 510P Spectrometer (Nicolet Instrument Inc., Madison, WI, USA).The analyses of C, H, and N were made on an Elementar Vario EL III elemental analyzer (Elementar, Hanau, Germany).1H NMR spectra were recorded on a Bruker Avance-400 spectrometer (Bruker, Elisabethhof, The Netherlands) with CH 3 COCH 3 as the solvent.Melting points were measured by using a melting point apparatus made in Shanghai Instrument Limited Company.The X-ray single-crystal data collection for the compounds 1 and 2 were performed on a Bruker Smart-1000 CCD diffractometer.

Preparation of Two Oxaspirocyclic Compounds
The synthetic route is shown in Scheme 1.

IR Spectra
The IR spectra of the two compounds show a little difference.The broad absorptions at 3265 cm −1 for 2 are assigned to the O-H stretching vibration of PhOH.The strong bands at 1705 cm −1 1 and 1745 cm −1 2, respectively, are due to the C=O stretching vibration of the 1,3-dioxane ring.The broad absorptions at 1167 cm −1 , 1126 cm −1 for 1 and at 1204 cm −1 , 1163 cm −1 for 2 are assigned to the C-O stretching vibration of the 1,3-dioxane ring.Meanwhile, a similar band at 1609 cm −1 and 1688 cm −1 was observed in the IR spectra of 1 and 2, respectively, indicting C=C stretching vibration of N(CH3)2−ph−C=C in 1 and HO−ph−C=C in 2. The IR spectra of the two compounds are in agreement with the structural data.

Materials and Methods
All the reagents and solvents from commercial sources were used without further purification.The IR spectra were recorded as KBr pellets with a Nicolet FT-IR 510P Spectrometer (Nicolet Instrument Inc., Madison, WI, USA).The analyses of C, H, and N were made on an Elementar Vario EL III elemental analyzer (Elementar, Hanau, Germany).1H NMR spectra were recorded on a Bruker Avance-400 spectrometer (Bruker, Elisabethhof, Netherlands) with CH3COCH3 as the solvent.Melting points were measured by using a melting point apparatus made in Shanghai Instrument Limited Company.The X-ray single-crystal data collection for the compounds 1 and 2 were performed on a Bruker Smart-1000 CCD diffractometer.

Preparation of Two Oxaspirocyclic Compounds
The synthetic route is shown in Scheme 1.

Crystallography
The structures of two compounds were solved by direct methods and refined by full-matrix least-squares techniques on F 2 using SHELXS-97 and SHELXL-97 programs [21].The non-hydrogen atoms were refined anisotropically.All hydrogen atoms were positioned with idealized geometry and were refined isotropic with an Uiso(H) = 1.2Ueq(C) of the corresponding parent atom using a riding model.The contributions of hydrogen atoms were included in the structure-factor calculations.The atomic scattering factors and anomalous dispersion corrections were taken from International Table for X-ray Crystallography [22].The final cycle of refinement gave R = 0.0570 and wR = 0.1667 (R = 0.0568 and wR = 0.1739 for 2) with w = 1/(σ

Figure 1 .
Figure 1.The molecular structures of 1 and 2 with the atomic numbering scheme.

Figure 1 .
Figure 1.The molecular structures of 1 and 2 with the atomic numbering scheme.
• .The two compounds have a similar structure.There are π•••π stacking interactions and some C−H•••O intra-and intermolecular hydrogen bonds in the two lattice structures.In addition, one type of C−H•••π supramolecular interaction in 1 is also present.One classical intermolecular hydrogen bond of O−H•••O is also observed in 2 (Tables

Figure 2 .
Figure 2. The packing arrangement in a unit cell of 1 and 2.

Figure 2 .
Figure 2. The packing arrangement in a unit cell of 1 and 2.

Table 1 .
Selected bond lengths (Å) and bond angles (°) of the two compounds.

and 2. Ring Symmetry Dihedral Angels (°) Distance Between Ring Centroids (Å) Perpendicular Distance of Cg(I) on Ring J(Å) Perpendicular Distance of
Cg(J) on Ring I(Å)

Table 4 .
Crystal and experimental data for 1 and 2.