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CRYSTAL GROWTH & DESIGN

Molecular Arrangement and Photoreaction of Sorbamides and Hexadienyl Carbamates with Various N-Substituents in the Solid State

2007 VOL. 7, NO. 7 1356-1364

Yutaka Mori, Tsuyoshi Chiba, Toru Odani, and Akikazu Matsumoto* Department of Applied Chemistry, Graduate School of Engineering, Osaka City UniVersity, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan ReceiVed April 16, 2007; ReVised Manuscript ReceiVed May 7, 2007

ABSTRACT: The crystal structure and solid-state photoreaction of sorbamides and 2,4-hexadienyl carbamates with various N-substituents have been investigated. One-dimensional (1D) hydrogen bond chains with a repeating distance of 5 Å were observed in their crystals, due to the strong intermolecular interaction between the CdO and N-H groups in the amide and carbamate moieties. We have revealed that N-benzylsorbamide and 2,4-hexadienyl N-(1-naphthyl)carbamate have a molecular stacking structure appropriate for the occurring [2+2] photodimerization and topochemical polymerization, respectively. The former sorbamide derivative gave a cyclodimer with an asymmetric structure, which was determined by NMR spectroscopy, under UV irradiation in the crystalline state. The γ-radiation of the latter carbamate derivative gave a polymer that is insoluble in any solvent. The polymer structure was determined by powder X-ray diffraction and IR spectroscopy. The reactivity in the solid-state photoreaction was discussed on the basis of the molecular stacking structures such as the stacking distance, the carbon-to-carbon distance, and the overlap of the π-orbitals. A twisted molecular conformation of the reacting diene planes against the carbamoyl planes connected with each other by the 1D hydrogen bonding is important for topochemical polymerization in the solid state. Introduction The structure-reactivity relationship has been investigated for organic reactions in the solid state to fabricate organic solid materials with well-controlled structures using crystal engineering.1 Solid-state reactions often give a unique product that cannot be obtained by a conventional reaction in an isotropic solution. The solid-state polymerization of diacetylene and diolefin compounds has been developed since the 1960s because of the advantageous feature of producing highly crystalline polymer materials with a well-defined chain structure. During the recent decade, we have reported the topochemical polymerization of various kinds of muconic and sorbic derivatives, which are one of the 1,3-diene mono- and dicarboxylate compounds.2,3 For the molecular stacking in the monomer crystals of the ester derivatives, weak intermolecular interactions such as CH/π4 and CH/O hydrogen bonds5 as well as halogen-halogen5a,6 interactions are important to design a crystal structure for the topochemical polymerization. On the other hand, a twodimensional (2D) hydrogen bond network consisting of carboxylate anions and primary ammonium cations as the triple hydrogen bond donors and the triple hydrogen bond acceptors, respectively, plays an important role in forming an appropriate molecular stacking structure leading to the polymerization.7 On an approach to molecular design using crystal engineering, an amide moiety is widely used because it has an acidic NH group capable of acting as the hydrogen bond donor and a carbonyl group as the hydrogen bond acceptor.8 In addition, the directivity of hydrogen bonds leads to a tunable and predictable molecular assembly for the design of the structural motifs in the solid state. In particular, a secondary amide is important for the construction of a supramolecular assembly in organic crystals. Nevertheless, the topochemical polymerization of the muconic and sorbic amide derivatives hardly occurs. In the 1980s, Tieke reported the polymerization of 6-amino-2,4-hexadinenoic acid derivatives * Corresponding author. Fax: +81-6-6605-2981. E-mail: matsumoto@ a-chem.eng.osaka-cu.ac.jp.

Chart 1

as well as N-octadecylsorbamide in the solid state.9 Later, we also reported the polymerization of N-alkyl- and N-(1-naphthylmethyl)sorbamides.10 However, the crystal structures of these sorbamide derivatives were not clarified. In the present study, we discuss the relationship between the crystal structure and the reactivity in the solid-state reaction of sorbamide and 2,4hexadienyl carbamate derivatives with various N-substituents (Chart 1). Results and Discussion Molecular Stacking in Sorbamide Crystals. Table 1 summarizes the crystallographic parameters determined by the X-ray single-crystal structure analysis of various N-substituted sorbamide derivatives. One-dimensional (1D) hydrogen bond

10.1021/cg070366o CCC: $37.00 © 2007 American Chemical Society Published on Web 06/19/2007

Photoreaction of Sorbamides and Hexadienyl Carbamates

Crystal Growth & Design, Vol. 7, No. 7, 2007 1357

Table 1. Crystallographic Data of N-Substituted Sorbamides 1-8 compounds

1

2

3

4

5

6

7

8

chemical formula fw cryst habit cryst syst space group T (K) a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Fcalc (g/cm3) no. of reflns measured no. of unique reflns no. obsd (I > 2σ (I)) R1 (I > 2σ (I)) wR2 (all) GOF

C12H13NO 187.23 platelet monoclinic P21/n 203 11.431(6) 8.625(4) 11.571(7) 90 116.38(4) 90 1022.1(9) 4 1.217 7861 2319 1674 0.0428 0.1260 1.025

C16H21NO 243.34 needle monoclinic P21/a 296 9.8398(5) 19.3105(11) 23.9105(13) 90 100.863(2) 90 4461.9(4) 12 1.087 10115 10115 4242 0.0810 0.2737 1.002




C17H17NO 251.32 block monoclinic P21 296 7.5223(16) 4.8304(11) 19.125(5) 90 91.465(7) 90 694.7(3) 2 1.201 4452 2324 1571 0.0572 0.1588 1.067

C18H19NO 265.34 needle orthorhombic P212121 296 4.8485(10) 13.756(4) 22.096(5) 90 90 90 1473.8(6) 4 1.196 12773 3371 2003 0.0667 0.1917 1.061

C13H15NO 201.26 needle orthorhombic Pbca 296 9.0770(9) 13.2357(15) 19.652(2) 90 90 90 2361.0(4) 8 1.132 21112 2688 1717 0.0749 0.1592 1.094

chains observed in the crystals are shown in Figure 1. The crystal of 1 includes a hydrogen bond with a 21 helical structure along the b-axis. 2 has a similar molecular packing structure, but the hydrogen bond is of the zigzag-type. Hydrogen bond motifs for 1 and 2 are classified as ribbon and tape types, respectively. The pattern for the molecular packing structures greatly changes due to the introduction of long-alkyl substituents. In the crystals of 3 and 4, monomer molecules are translationally arranged in the direction of an axis to form a sheet structure. The N-benzyl and naphthylmethyl substitutions also give a similar molecular stacking pattern (5-7). The periodic distance for the 1D intermolecular hydrogen bond of the amide groups is 5.055.17 Å for 3 and 4 and 4.83-4.88 Å for 5-7, in which the intermolecular interaction between the alkyl chains and aromatic groups supports each stacking structure. The latter interaction includes π/π and CH/π interactions, resulting in a robust stacking structure and a shorter repeating distance. These stacking distances close to 5 Å seem to be appropriate for the topochemical polymerization of 1,3-diene compounds, but no polymerization actually occurred for the amide derivatives 1-7. This is due to the unfavorable stacking direction of the diene moiety as well as the difficulty in their conformational change during the reaction. In our previous communication,10 the topochemical polymerization of 6 was reported, but the crystals obtained in the present study were completely inactive. This is due to the polymorphs of compound 6. The slow evaporation of the methanol or 1,2-dichloroethane solution of 6 resulted in the growth of needle crystals, which had no polymerizability. The powdery and polymerizable crystals were obtained by fast evaporation. A single-crystal structure for the polymerizable crystal was not determined in the previous paper, but the powder X-ray diffraction profiles of both crystals are different. It was speculated that the polymerization occurred in the inter-sheet direction but not along the direction of the 1D hydrogen bond in the sheet, as was already described in the previous paper.10 From the crystal structures of N-substituted sorbamide derivatives, it is clear that the molecules are stacked at a distance of 5 Å by the formation of a linear hydrogen bond chain between the CdO and N-H groups, but the diene planes are arranged in an edge-to-edge fashion. The direction of the diene plane stacking (i.e., the overlap of π-orbitals of the adjacent diene molecules) is not appropriate for the reaction. When a diene group is twisted against the 1D hydrogen bond chain, the crystal

structure changes to that in the face-to-face type at a repeating distance of 5 Å, which is just suitable for the topochemical polymerization. We tried to change the molecular conformation in the monomer crystals by introducing a methyl group on the β-position of the sorbamide skeleton, but this attempt resulted in the formation of a nonlinear and twisted intermolecular hydrogen bond structure, as shown in the crystal structure of 8 in Figure 1h. [2+2] Photodimerization of Sorbamide. In the present study, we found no sorbamide crystal that underwent topochemical polymerization, but we noticed the intermolecular close contact of the monomer molecules in the crystal of 5. The close contact of the diene moieties is shown in Figure 2. The center-to-center distance between the adjacent double bonds (dCC) was 4.11-6.07 Å in the structure of case 1. The couples of double bonds are arranged in non-parallel fashion in this case. On the other hand, the double bonds are arranged in parallel fashion with dCC values of 3.96 and 3.99 Å in the structure of case 2. When the crystal of 5 was exposed under UV irradiation for 60 h at room temperature, it gave a dimer in a 24% yield. The product was isolated by silica gel column chromatography, and its chemical structure was determined by NMR spectroscopy. The obtained 1H and 13C NMR spectra are shown in Figure 3, together with the assignment for the produced dimer structure.11 Four kinds of methine carbons (observed at 43.66, 43.55, 41.02, and 35.39 ppm) and protons (observed at 3.443.50, 2.87-2.95, 2.56-2.64 ppm) as the cyclobutane ring structure and two independent olefin carbons and protons (observed at 144.87, 129.75, 127.91, and 123.55 ppm for C and 5.44-5.76 ppm for H) were detected in the spectra. These spectral features strongly suggest the formation of a dimer with an asymmetric structure. As shown in Figure 4, there is the possibility of the formation of several kinds of [2+2] photodimers from a sorbamide, depending on the type of molecular stacking and the position of the reacting double bonds. For example, when two diene moieties are arranged in a parallel fashion, three kinds of products can be produced by [2+2] cyclization. On the other hand, dimerization between the molecules that are arranged in a column with an antiparallel stacking would provide two kinds of dimers. The crystal of 5 favors the latter stacking structure, and the NMR data supports the formation of a type IV dimer. For the sorbamide derivatives other than 5, we found no close

1358 Crystal Growth & Design, Vol. 7, No. 7, 2007

Mori et al.

Figure 1. Crystal structure and 1D hydrogen bond of N-substituted sorbamides. (a) 1, (b) 2, (c) 3, (d) 4, (e) 5, (f) 6, (g) 7, and (h) 8.

contact in their crystals and also no dimerization product under UV irradiation conditions Solid-State Reaction and Crystal Structure of 2,4-Hexadienyl Carbamates. A change in the torsion angle between the diene moiety and the amide group in the monomer crystal would result in the occurrence of topochemical polymerization. On the basis of this concept, we introduced a spacer between the dienyl group and the amide group. Considering the merit for facile monomer preparation, we synthesized various N-substituted 2,4-hexadienyl carbamates 9-14 (see Chart 1 for their chemical structure) and examined their reactivity in the solidstate reaction under various conditions, e.g., under UV irradia-

tion with a high-pressure Hg lamp at room temperature and upon heating. As a result, no reaction occurred for compounds 9-13, but we noticed the formation of a product when the crystals of 14 were irradiated with UV light at 80 °C for 24 h. An insoluble product was obtained in 8% yield after the irradiation. Furthermore, we also confirmed the presence of three kinds of polymorphs for the 14 crystals. Each crystal was separately obtained as 14a-14c, which were provided for the powder X-ray diffraction measurement to determine their crystal structure. The obtained diffraction profiles of each polymorph are shown in Figure 5. One of the polymorphic crystals 14a was readily obtained by recrystallization from a methanol



Figure 2. (a) Close contact of diene moieties observed in the crystal of 5. (b) Views down along the crystallographic a-axis.

solution of 14. Another polymorph 14c was obtained by the slow cooling of a hot hexane solution. The fast cooling of the same hexane solution often gave 14a. The polymorph 14b was very seldom obtained, and the detailed conditions for crystal growth are unknown, although we actually obtained it as shown in the X-ray diffraction profile in Figure 5b. The photoreaction of 14c yielded an insoluble product, while no reaction occurred for 14a and 14b. Therefore, the solid-state reactions and the crystal structure of 14 were further investigated. The γ-radiation polymerization of 14c occurred at a relatively low rate. When the radiation dose was 1000 kGy, the polymer was quantitatively formed. The reactivity of 14c for the γ-radiation polymerization is low, compared with those for the other polymerizable muconic ester and ammonium derivatives previously reported.12,13 The structure of the product was confirmed by powder X-ray diffraction (Figure 5d) and IR spectroscopy (Figure 6) because the product was insoluble in any solvent, for example, methanol, acetone, n-hexane, toluene, chloroform, dimethyl sulfoxide, N,N-dimethylformamide, N-methyl-2-pyrolidone, and 1,2-dichlorobenzene. We also tested the solubility in 1,2-dichlorobenzene with refluxing, but the polymer was insoluble. As shown in Figure 6, the absorbance due to the stretching of the CdC bond shifted from 986 to 972 cm-1 according to the change in the chemical structure from 1,3diene to olefin. This result supports the occurrence of topochemical polymerization. The shift of a band due to the N-H stretching was also observed from 3263 or 3280 cm-1. This may be due to a change in the hydrogen bond distance and conformation. In the powder X-ray diffraction of 14c (Figure 5), the diffraction line due to the 100 plane was observed at 2θ ) 19.29°. The similar diffraction line was also detected at 2θ ) 19.30° in the profile of poly(14c). However, further discussion about the change in the crystal structure during the polymeri-

Figure 3. (a) 1H and (b) 13C NMR spectra of a photodimer produced from 5 under UV irradiation in the crystalline state. The product was isolated by silica gel column chromatography.

zation of 14c cannot be carried out in the present study because of the low reactivity of the 14c crystals and no single-crystal structure of poly(14c). In the present study, we successfully determined the singlecrystal structures of some N-substituted carbamate derivatives. The crystallographic data and the crystal structures for 14a and 14c are shown in Table 3 and Figure 7, together with the results for 13. No single crystal of 14b was obtained. The 1D hydrogen bond was observed along the crystallographic a-axis for 13 and 14c and the b-axis for 14a, as seen in Figure 7. This is similar to the crystals of the N-substituted sorbamides (Figure 1). The stacking structures of 14a and 14c are very similar. The ORTEP drawing also shows a similar molecular conformation for 14a and 14c, which include a twisting structure between the dienyl and the carbamoyl groups as expected. We can find the smallest ds and dCC values for 14c as the polymerizable crystal, as shown in Table 3. The polymerization of the carbamate derivatives seems to require a ds value smaller than those for the polymerization of muconates and sorbates, that is, 4.8-5.2 Å for the polymerizable crystals of 1,3-diene monomers.2d,14 The overlapping of the π-orbitals was formed in the columnar stacking of the monomer molecules with an appropriate stacking distance, resulting in the polymer formation under γ-radiation. In conclusion, we have revealed the crystal structures of sorbamide and 2,4-hexadienyl carbamate derivatives with various N-substituents by X-ray single-crystal structure analysis. The sorbamide derivatives formed a sheet assembly supported by a linear (1D) intermolecular hydrogen bond chain between the CdO and N-H groups. The diene moieties are stacked in an edge-to-edge form along the direction of the hydrogen bond


Mori et al.

Figure 4. Formation of [2+2] cyclodimers from a sorbamide derivative in the crystal with (a) translational and (b) antiparallel monomer stacking structures.

Figure 5. Wide-angle powder X-ray diffraction profiles of (a) 14a, (b) 14b, (c) 14c, and (d) poly(14c) obtained after γ-radiation at a dose of 1000 kGy.

chains, and therefore, no polymerization occurred. On the other hand, one of the carbamate derivatives has an overlapped structure of the π-orbitals of the diene moieties, leading to the successful polymerization in the solid state. Thus, the introduction of a spacer into the monomer structure between the dienyl group as the reacting center and the carbamoyl group induces the flexible molecular conformation, leading to polymerization. The crystal structure and the solid-state reaction relationship obtained in the present study gives us valuable and additional information about structural design for organic solid-state reactions using the amide and carbamate derivatives of 1,3diene monomers. Experimental Section Measurements. The NMR and IR spectra were recorded using JEOL JMN A-400 and JASCO Herschel FT-IR-430 spectrometers, respectively. The UV spectra were taken using a JASCO V-550 photometer. The powder X-ray diffraction profile was measured using a RIGAKU X-ray diffractometer RINT-2200 with monochromatized Cu KR radiation (λ ) 1.54184 Å). The X-ray crystallographic data were collected using a Rigaku R-AXIS RAPID system with graphite monochromated Mo KR radiation (λ ) 0.71073 Å). The structure was solved by direct methods using SIR92 and SHELXS-97 and refined by the full-matrix least-squares method on F2 with anisotropic displacement parameters for non-hydrogen atoms using SHELXL-97.15

Figure 6. IR spectra of (a) 14c and (b) poly(14c) obtained after γ-radiation at a dose of 1000 kGy.

Materials. N-Substituted sorbamides were synthesized from sorbic acid chloride and the corresponding amine. The sorbic acid chloride was obtained from sorbic acid (2.5 g, 22 mmol) and thionyl chloride (2.0 mL) in the presence of a drop of N,Ndimethylformamide in 50 mL of 1,2-dichloroethane with refluxing for a half-hour. The obtained acid chloride was added dropwise to a 1,2-dichloroethane solution (50 mL) containing the corresponding amine (22 mmol) and triethylamine (2.3 g) with stirring at room temperature. After the sample was further stirred at room temperature for 1 day, the solvent was evaporated. The product was purified by silica gel column chromatography with chloroform. The isolated N-substituted sorbamide derivatives were recrystallized from 1,2-dichloroethane, chloroform, and ethyl acetate. The yield was 21-97%. N-Phenylsorbamide (1): platelet, mp 120-121 °C; 1H NMR (CDCl3, 400 MHz) δ 7.57 (broad, NH, 1H), 7.36-7.09 (m, Ar



Table 2. γ-Radiation Polymerization of N-Substituted 2,4-Hexadienyl Carbamates in the Solid State at Room Temperature compound 13 14a 14b 14c di(benzylammonium) (Z,Z)-muconate diethyl (Z,Z)-muconate di(4-chlorobenzyl) (Z,Z)-muconate bis(3,4-dimethylenedioxybenzyl) (E,E)-muconate

dose (kGy)

polymer yield (%)

ref

1000 1000 1000 500 1000 10

no reaction no reaction no reaction 86 ∼100 87

this work this work this work this work this work 12

10 50 100 500 1000

∼100 96 ∼100 92 ∼100

12 13 13 13 13

Table 3. Crystallographic Data, Stacking Parameters, and Torsion Angles for N-Substituted 2,4-Hexadienyl Carbamates compounds

13

14a

14c

chemical formula fw cryst habit cryst syst space group T (K) a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Fcalc (g/cm3) no. of reflns measured no. of unique reflns no. obsd (I > 2σ (I)) R1 (I > 2σ (I)) wR2 (all) GOF ds (Å) dCC (Å) θ1 (deg) θ2 (deg) N-H‚‚‚O distance (Å) N-H‚‚‚O angle (deg) C(4)-C(5)-C(6)-O(1) (deg) C(5)-C(6)-O(1)-C(7) (deg) C(6)-O(1)-C(7)-O(2) (deg) C(6)-O(1)-C(7)-N(1) (deg) O(1)-C(7)-N(1)-C(8) (deg) O(2)-C(7)-N(1)-C(8) (deg)

C13H15NO2 217.26 platelet orthorhombic P212121 123 5.043(2) 7.064(3) 32.897(13) 90 90 90 1171.9(9) 4 1.231 11203 2695 2316 0.0725 0.2083 1.074 5.04 5.28 42 65 2.07 167.9 110.2(5) 76.3(4) 10.0(5) 170.3(3) 170.6(3) 9.1(5)

C17H17NO2 267.32 needles monoclinic P21/c 123 17.426(7) 4.757(2) 18.249(8) 90 108.36(4) 90 1435.8(11) 4 1.237 11545 3104 2351 0.0511 0.1281 1.056 4.76 5.69 43 81 1.96 166.4 134.95(17) 170.04(14) 1.7(2) 178.50(14) 177.44(13) 2.7(3)

C17H17NO2 267.32 needles triclinic P1h 123 4.6807(18) 12.728(5) 13.782(6) 64.00(3) 81.56(3) 80.17(4) 724.7(5) 2 1.225 5759 3120 1274 0.0582 0.1381 0.823 4.68 5.19 45 71 1.95 162.9 127.7(3) 171.9(2) 0.1(4) 179.9(2) 176.9(2) 3.1(5)

and CHdCHCO, 6H), 6.18 (m, CH3CHdCH, 2H), 5.89 (d, J ) 15.2 Hz, CHdCHCO, 1H), 1.87 (d, J ) 5.6 Hz, CH3CHd CH, 3H); 13C NMR (CDCl3, 100 MHz) δ 164.65 (CdO), 142.57 (CHdCHCO), 138.14 (CH3CHdCH), 129.59 (CH3CHdCH), 121.69 (CHdCHCO), 138.14, 128.93, 124.14, and 119.90 (Ar), 18.62 (CH3CHdCH); IR(KBr) 1629 (νCdC), 1596 (νCdO) cm-1. N-4-n-Butylphenylsorbamide (2): needles, mp 119 °C; 1H NMR (CDCl3, 400 MHz) δ 7.46 and 7.14 (m, Ar, 4H), 7.32 (dd, J ) 10.4 and 14.4 Hz, CHdCHCO, 1H), 7.10 (broad, NH, 1H), 6.17 (m, CH3CHdCH, 2H), 5.87 (d, J ) 14.4 Hz, CHd CHCO, 1H), 2.58 (t, J ) 8.0 Hz, ArCH2, 2H), 1.87 (d, J ) 6.0 Hz, CH3CHdCH, 3H), 1.57 (m, ArCH2CH2, 2H), 1.34 (m, CH2CH3, 2H), 0.92 (t, J ) 7.2 Hz, CH2CH3, 3H); 13C NMR (CDCl3, 100 MHz) δ 164.34 (CdO), 142.39 (CHdCHCO), 138.61 (CH3CHdCH), 129.62 (CH3CHdCH), 121.76 (CHdCHCO), 138.92, 135.71, 128.86, and 119.85 (Ar), 35.06, 33.64, and 22.27 (CH2), 18.65 (CH3CHdCH), 13.93 (CH3); IR (KBr) 1635 (νCdC), 1597 (νCdO) cm-1; UV(CH3OH) λmax 271 nm ( ) 28000). N-4-n-Octylphenylsorbamide (3): needles, mp 120 °C; 1H NMR (CDCl3, 400 MHz) δ 7.46 and 7.14 (m, Ar, 4H), 7.32

(dd, J ) 10.4 and 15.2 Hz, CHdCHCO, 1H), 7.12 (broad, NH, 1H), 6.17 (m, CH3CHdCH, 2H), 5.88 (d, J ) 15.2 Hz, CHd CHCO, 1H), 2.56 (t, J ) 8.0 Hz, ArCH2, 2H), 1.86 (d, J ) 5.6 Hz, CH3CHdCH, 3H), 1.59 (m, ArCH2CH2, 2H), 1.27 (m, CH2, 10H), 0.88 (t, J ) 6.8 Hz, CH2CH3, 3H); 13C NMR (CDCl3, 100 MHz) δ 164.39 (CdO), 142.34 (CHdCHCO), 138.54 (CH3CHdCH), 129.62 (CH3CHdCH), 121.79 (CHdCHCO), 138.92, 135.71 128.81, and 119.86 (Ar), 35.37, 31.87, 31.50, 29.45, 29.25, and 22.65 (CH2), 18.64 (CH3CHdCH), 14.10 (CH3); IR (KBr) 1633 (νCdC), 1596 (νCdO) cm-1; UV(CH3OH) λmax 271 nm ( ) 30200). N-4-n-Dodecylphenylsorbamide (4): needles, mp 118 °C; 1H NMR (CDCl3, 400 MHz) δ 7.46 and 7.14 (m, Ar, 4H), 7.31 (dd, J ) 10.0 and 14.4 Hz, CHdCHCO, 1H), 7.12 (broad, NH, 1H), 6.17 (m, CH3CHdCH, 2H), 5.87 (d, J ) 14.8 Hz, CHd CHCO, 1H), 2.56 (t, J ) 8.0 Hz, ArCH2, 2H), 1.86 (d, J ) 5.6 Hz, CH3CHdCH, 3H), 1.59 (m, ArCH2CH2, 2H), 1.28 (m, CH2, 18H), 0.88 (t, J ) 6.8 Hz, CH2CH3, 3H); 13C NMR (CDCl3, 100 MHz) δ 164.59 (CdO), 142.26 (CHdCHCO), 138.44 (CH3CHdCH), 129.65 (CH3CHdCH), 121.89 (CHdCHCO), 138.88, 135.76, 128.77, and 119.93 (Ar), 35.37, 31.88, 31.50, 29.63, 29.32, 29.27, and 22.65 (CH2), 18.60 (CH3CHdCH), 14.10 (CH3); IR (KBr) 1633 (νCdC), 1597 (νCdO) cm-1; UV(CH3OH) λmax 271 nm ( ) 28800). N-Benzylsorbamide (5): needles, mp 131 °C; 1H NMR (CDCl3, 400 MHz) δ 7.35-7.20 (m, Ar and CHdCHCO, 6H), 6.12 (m, CH3CHdCH, 2H), 5.77 (broad, NH, 1H), 5.75 (d, J ) 15.2 Hz, CHdCHCO, 1H), 4.52 (d, J ) 6.0 Hz, CH2, 2H), 1.83 (d, J ) 6.0 Hz, CH3CHdCH, 3H); 13C NMR (CDCl3, 100 MHz) δ 166.18 (CdO), 141.40 (CHdCHCO), 137.78 (CH3CHdCH), 129.62 (CH3CHdCH), 121.31 (CHdCHCO), 137.07, 135.38, 129.28, and 127.83 (Ar), 43.35 (CH2), 18.54 (CH3CHd CH); IR (KBr) 1654 (νCdC), 1616 (νCdO) cm-1; UV(CH3OH) λmax 258 nm ( ) 47800). N-(1-Naphthylmethyl)sorbamide (6): needles, mp 182 °C; 1H NMR (CDCl , 400 MHz) δ 8.04-7.41 (m, Ar, 7H), 7.24 3 (dd, J ) 10.0 and 14.8 Hz, CHdCHCO, 1H), 6.11 (m, CH3CHd CH, 2H), 5.69 (d, J ) 14.8 Hz, CHdCHCO and broad, NH, 2H), 4.97 (t, J ) 5.2 Hz, NHCH2, 2H), 1.82 (d, J ) 7.2 Hz, CH3CHdCH, 3H); 13C NMR (CDCl3, 100 MHz) δ 165.95 (Cd O), 141.73 (CHdCHCO), 138.13 (CH3CHdCH), 129.59 (CH3CHdCH), 121.02 (CHdCHCO), 133.87, 133.52, 131.41, 128.73, 128.67, 126.87, 126.69, 126.02, 125.39, and 123.60 (Ar), 41.90 (CH2), 18.59 (CH3CHdCH); IR (KBr) 1655 (νCdC), 1627 (νCdO) cm-1; UV(CH3OH) λCdC 261 nm ( ) 37700). (S)-N-(1-(1-Naphthyl)ethyl)sorbamide (7): needles, mp 188 °C; 1H NMR (CDCl3, 400 MHz) δ 8.12-7.44 (m, Ar, 7H), 7.22 (dd, J ) 10.0 and 14.8 Hz, CHdCHCO, 1H), 6.09 (m, CH3CHdCH, 2H), 6.02 (m, NHCH), 5.66 (d, J ) 14.8 Hz, CHdCHCO and broad, NH, 2H), 1.82 (d, J ) 5.6 Hz, CH3CHdCH, 3H), 1.71 (d, J ) 6.8 Hz, NHCH(CH3)Ar, 3H); 13C NMR (CDCl3, 100 MHz) δ 165.21 (CdO), 141.57 (CHd CHCO), 137.96 (CH3CHdCH), 129.56 (CH3CHdCH), 121.21 (CHdCHCO), 138.13, 133.85, 131.13, 128.67, 128.34, 126.58, 125.84, 125.13, 123.50, and 122.59 (Ar), 44.55 (CH), 20.53 (CHCH3), 18.55 (CH3CHdCH); IR (KBr) 1656 (νCdC), 1631 (νCdO) cm-1; UV(CH3OH) λmax 261 nm ( ) 28600). N-Phenyl (2E,4E)-2-methyl-2,4-hexadienamide was synthesized from (2E,4E)-2-methyl-2,4-hexadienoic acid chloride and phenylamine in the same way as described above. The synthesis of (2E,4E)-2-methyl-2,4-hexadienoic acid is as follows: sodium hydride in oil (1.9 g) was dissolved in dry THF (100 mL) under a nitrogen atmosphere, and triethyl 2-phosphonopropionate (6.8 g) was added dropwise under


Mori et al.

Figure 7. Crystal structure and the ORTEP drawing of (a) 13, (b) 14a, and (c) 14c. One-dimensional hydrogen bond chains are observed along the crystallographic a-axis (13 and 14c) and b-axis (14a).

Figure 8. Numbering of atoms for the determination of torsion angles in Table 3.

stirring to the solution. Further, dry THF solution containing crotonaldehyde (2.3 g) was slowly dropped into the solution over 1 h at 0 °C. After the reaction was stirred for 1 day, the reaction solution was filtered, and the solvent was evaporated under reduced pressure. (2E,4E)-2-Methyl-2,4-hexadienoic acid ethyl ester was isolated by silica gel column chromatography with a mixture of hexane and ethyl acetate (5:1 in volume). The ester was then dissolved in methanol, and potassium hydroxide aqueous solution was added to the methanol solution at a molar ratio of 1:1. After the sample was refluxed for a few hours, the methanol was evaporated under reduced pressure, and hydrochloric acid (2.0 mol/L) was added dropwise to the solution until it became acidic. (2E,4E)-2-Methyl-2,4-hexadienoic acid was obtained in a 44% yield by extraction with ethyl acetate and evaporation of the solvent.

N-Phenyl-(2E,4E)-2-methyl-2,4-hexadienamide (8): needles, mp 105 °C; 1H NMR (CDCl3, 400 MHz) δ 7.57, 7.31 and 7.10 (m, Ar, 5H and broad, NH, 1H), 6.94 (d, J ) 10.8 Hz, CHd C(CH3)CO, 1H), 6.36 (m, CH3CHdCH, 1H), 6.05 (m, CH3CHd CH, 1H), 2.03 (s, CHdC(CH3)CO, 3H), 1.87 (d, J ) 6.8 Hz, CH3CHdCH, 3H); 13C NMR (CDCl3, 100 MHz) δ 167.55 (Cd O), 136.76 (CHdC(CH3)CO), 134.43 (CH3CHdCH), 128.17 (CHdC(CH3)CO), 127.00 (CH3CHdCH), 138.11, 128.91, 124.11, and 120.03 (Ar), 18.83 (CH3CHdCH), 12.94 (CHd C(CH3)CO); IR (KBr) 1626 (νCdC), 1594 (νCdO) cm-1; UV(CH3OH) λmax 268 nm ( ) 24300). All 2,4-hexadienyl N-substituted carbamates were prepared by the following procedure. An example of the synthesis is shown below: To prepare 12, a mixture of trans,trans-2,4-hexadien-1-ol (1.4 g), benzyl isocyanate (2.0 g), and a small amount of pyridine were dissolved in toluene (10 mL), and this was refluxed for 2 h. After the sample was cooled to room temperature, the solution was washed with water and extracted with chloroform. After the sample as dried with anhydrous sodium sulfate, the solution was filtered, and the solvent was evaporated from the filtrate.


The product was purified by silica gel column chromatography with chloroform and dried in vacuo at room temperature. Yield was 93%. Bis(2,4-hexadienyl) N,N-1,6-hexylenedicarbamate (9): powder, mp 96 °C; 1H NMR (400 MHz, CDCl3) δ 6.20-6.27 (m, CHdCHCH2, 2H), 6.02-6.08 (m, CH3CHdCH, 2H), 5.695.78 (m, CHdCHCH2, 2H), 5.59-5.66 (m, CH3CHdCH, 2H), 4.80 (broad, NH, 2H), 4.55 (d, J ) 6.4 Hz, OCH2, 4H), 3.16 (q, J ) 6.4 Hz, NHCH2, 4H), 1.76 (d, J ) 6.8 Hz, CH3CHd CH, 6H), 1.49 (broad, NHCH2CH2, 4H), 1.32 (broad, NHCH2CH2CH2, 4H); 13C NMR (100 MHz, CDCl3) δ 156.41 (CdO), 134.32 (CHdCHCH2), 130.93 (CH3CHdCH), 130.53 (CHd CHCH2), 124.53 (CH3CHdCH), 65.19 (OCH2), 40.77 (NHCH2), 29.88 (NHCH2CH2), 26.21 (NHCH2CH2CH2), 18.13 (CH3CHd CH). Bis(2,4-Hexadienyl) N,N-1,4-phenylenedicarbamate (10): powder, mp 181 °C; 1H NMR (400 MHz, DMSO) δ 7.34 (s, Ph, 4H), 6.27-6.33 (m, CHdCHCH2, 2H), 6.06-6.13 (m, CH3CHdCH, 2H), 5.65-5.77 (m, CHdCHCH2, CH3CHdCH, 4H), 4.58 (d, J ) 6.4 Hz, OCH2, 4H), 1.73 (d, J ) 6.8 Hz, CH3CHdCH, 6H); 13C NMR (100 MHz, DMSO) δ 153.40 (Cd O), 133.93 (ipso-Ph), 133.82 (CHdCHCH2), 130.64 (CH3CHd CH), 130.56 (CHdCHCH2), 125.03 (CH3CHdCH), 118.76 (oPh), 64.30 (OCH2), 17.96 (CH3CHdCH). 2,4-Hexadienyl N-cyclohexylcarbamate (11): plates, mp 9596 °C; 1H NMR (400 MHz, CDCl3) δ 6.20-6.27 (m, CHd CHCH2, 1H), 6.02-6.08 (m, CH3CHdCH, 1H), 5.69-5.78 (m, CHdCHCH2, 1H), 5.59-5.66 (m, CH3CHdCH, 1H), 4.60 (broad, NH, 1H), 4.54 (d, J ) 6.4 Hz, OCH2, 2H), 3.47 (broad, R-CH, 1H), 1.76 (d, J ) 6.8 Hz, CH3CHdCH, 3H), 1.072.17 (cyclohexyl); 13C NMR (100 MHz, CDCl3) δ 155.51 (Cd O), 134.32 (m, CHdCHCH2, 1H), 130.89 (CH3CHdCH), 130.55 (CHdCHCH2), 124.58 (CH3CHdCH), 65.06 (OCH2), 49.77 (R-CH), 33.42 (β-CH2), 25.49 (δ-CH2), 24.78 (γ-CH2), 18.13 (CH3CHdCH). 2,4-Hexadienyl N-benzylcarbamate (12): powder, mp 47 °C; 1H NMR (400 MHz, CDCl ) δ 7.26-7.35 (m, Ph, 5H), 6.223 6.25 (m, CHdCHCH2, 1H), 6.02-6.08 (m, CH3CHdCH, 1H), 5.71-5.77 (m, CHdCHCH2, 1H), 5.60-5.67 (m, CH3CHdCH, 1H), 5.00 (broad, NH, 1H), 4.60 (d, J ) 6.4 Hz, OCH2, 2H), 4.37 (d, J ) 5.6 Hz, NHCH2, 2H), 1.76 (d, J ) 6.8 Hz, CH3CHdCH, 3H); 13C NMR (100 MHz, CDCl3) δ 156.24 (CdO), 138.42, 133.80, 130.30, 133.23, 128.06, 127.02, 126.79, and 124.19 (C6H5 and CHd), 64.91 (OCH2), 44.44 (NHCH2), 17.70 (CH3CHdCH). 2,4-Hexadienyl N-phenylcarbamate (13): platelet, mp 41 °C; 1H NMR (400 MHz, CDCl ) δ 7.28-7.39 (m, o-Ph, m-Ph, 4H), 3 7.06 (t, J ) 7.2 Hz, p-Ph, 1H), 6.60 (broad, NH, 1H), 6.276.33 (m, CHdCHCH2, 1H), 6.04-6.10 (m, CH3CHdCH, 1H), 5.74-5.80 (m, CHdCHCH2, 1H), 5.65-5.69 (m, CH3CHdCH, 1H), 4.66 (d, J ) 6.4 Hz, OCH2, 2H), 1.77 (d, J ) 6.8 Hz, CH3CHdCH, 3H); 13C NMR (100 MHz, CDCl3) δ 155.51 (Cd O), 137.80, 134.92, 131.35, 130.33, 128.95, 123.75, 123.34, and 118.63 (C6H5 and CHd), 65.61 (OCH2), 18.09 (CH3CHdCH). 2,4-Hexadienyl N-(1-naphthyl) carbamate: needles, mp 99101 °C for (14a); needles, mp 93-95 °C for (14b); needles, mp 96-97 °C for (14c); 1H NMR (400 MHz, CDCl3) δ 7.457.88 (m, C12H7, 7H), 6.95 (broad, NH, 1H), 6.29-6.33 (m, CHd CHCH2, 1H), 6.06-6.12 (m, CH3CHdCH, 1H), 5.70-5.81 (m, CHdCHCH2, CH3CHdCH, 2H), 4.73 (d, J ) 6.8 Hz, OCH2, 2H), 1.78 (d, J ) 6.0 Hz, CH3CHdCH, 3H); 13C NMR (100 MHz, CDCl3) δ 154.20 (CdO), 135.05, 133.98, 132.40, 131.41, 130.36, 128.65, 126.66, 126.15, 125.92, 125.74, 124.95, 123.76,


120.42, and 118.99 (C10H7 and CHd), 65.91 (OCH2), 18.13 (CH3CHdCH); IR (KBr) 1693 (νCdO), 986 (νCdC) cm-1. Photoreactions. The photoreaction of N-substituted sorbamides and carbamates in the crystalline state was carried out in a degassed Pyrex tube under UV irradiation with a high-pressure mercury lamp (Toshiba SHL-100-2, 100W, Pyrex filter) for 60 h at room temperature. For the reaction of 5, the photoproduct was isolated by silica gel column chromatography with a mixed solvent (chloroform/ethyl acetate ) 9/1 in volume ratio). Dimer of 5: Yield 24%. 1H NMR (CDCl3, 400 MHz) δ 7.28-7.36 (Ar, 10H), 6.92-6.98 (1H), 5.72-5.76 (2H), 5.64 (1H), 5.44-5.56 (2H), 4.40-4.56 (4H), 3.44-3.50 (1H), 2.872.95 (2H), 2.56-2.64 (1H), 1.64-1.66 (3H), 1.10-1.12 (3H); 13C NMR (CDCl , 100 MHz) δ 172.04, 165.43, 144.87, 138.33, 3 138.19, 129.75, 128.72, 127.91, 127.84, 127.52, 123.55, 46.43, 46.35, 43.66, 43.55, 41.02, 35.39, 17.96, and 15.56. γ-Radiation. The crystals were charged into a Pyrex tube and degassed, and the tube was then sealed. γ-Radiation was carried out with 60Co at room temperature. After the γ-radiation, the contents of the tube were poured into a large amount of chloroform and stirred at room temperature overnight. The product was filtered and dried in vacuo. The structure of the product was determined by powder X-ray diffraction and IR spectroscopy. The soluble part was also examined by NMR spectroscopy. Poly(14c): colorless needles; insoluble in organic solvents; IR (KBr) 1693 (νCdO), 972 (νCdC) cm-1, powder X-ray diffraction: 2θ (deg) 6.94, 8.06, 9.14, 11.98, 14.10, 15.82, 16.18, 17.90, 19.30, 20.32, 20.92, and 24.12. Acknowledgment. This work was supported by Grants-inAid for Scientific Research on Priority Areas (Area No. 432, No. 16072215) and for Scientific Research (No. 16350067) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. The authors gratefully thank Prof. Kunio Oka, Osaka Prefecture University, for his kind assistance with the γ-radiation experiments. Supporting Information Available: X-ray crystallographic information files (CIF). The materials are available free of charge via the Internet at http://pubs.acs.org.

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