The title compound, C
17H
24O
4, crystallizes with two independent molecules, both lying across twofold rotation axes in space group
Pccn, in a unit cell whose dimensions closely mimic those of a tetragonal cell. Each molecule contains paired O—H
O hydrogen bonds [H
O = 1.81 and 1.83 Å, O
O = 2.640 (2) and 2.642 (2) Å, and O—H
O = 168 and 162°].
Supporting information
CCDC reference: 229094
To a solution of 2-methoxy-4-aminopyrimidin-6(1H)-one (2.12 mmol) and dimedone (1.92 mmol) in ethanol (30 ml) was added a large excess (26.5 mmol) of formaldehyde (35% aqueous solution). The mixture was then heated under reflux for 2 h and the resulting white solid was filtered off and washed with cold ethyl acetate and then with ethanol. This product was purified crystallization firstly from ethanol/water (9:1, v/v) and then from N,N-dimethylformamide, giving, in very low yield, crystals of the title compound, (II), suitable for single-crystal X-ray diffraction analysis. M.p. 463 K. Analysis found: C 69.5, H 8.5%; C17H24O4 requires C 69.8, H, 8.3%. The same product was obtained in ca 70% yield in the absence of the pyrimidinone. To a solution of dimedone (2 mmol) in ethanol (10 ml) was added formaldehyde (35% aqueous solution, 1 mmol). The mixture was stirred at room temperature for 2 h and then left to evaporate at atmospheric pressure, producing (II).
Space group Pccn was uniquely assigned from the systematic absences. All H atoms were located from difference maps and then treated as riding atoms, with C—H = 0.98 (CH3) or 0.99 Å (CH2), and O—H = 0.84 Å. A TWIN refinement using the matrix (010/100/001) gave twin fractions 0.468 and 0.532. Examination of the refined structure using the ADDSYM option in PLATON (Spek, 2003) revealed no possible additional symmetry.
Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).
2,2'-Methylenebis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one)
top
Crystal data top
C17H24O4 | F(000) = 1264 |
Mr = 292.36 | Dx = 1.249 Mg m−3 |
Orthorhombic, Pccn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ab 2ac | Cell parameters from 3552 reflections |
a = 18.8968 (4) Å | θ = 3.1–27.5° |
b = 18.8989 (4) Å | µ = 0.09 mm−1 |
c = 8.7038 (2) Å | T = 120 K |
V = 3108.38 (12) Å3 | Block, colourless |
Z = 8 | 0.22 × 0.20 × 0.10 mm |
Data collection top
Nonius KappaCCD diffractometer | 3552 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 2991 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.080 |
ϕ scans, and ω scans with κ offsets | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | h = −24→20 |
Tmin = 0.973, Tmax = 0.991 | k = −24→24 |
22526 measured reflections | l = −9→11 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.047 | H-atom parameters constrained |
wR(F2) = 0.116 | w = 1/[σ2(Fo2) + (0.0453P)2 + 1.0196P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max < 0.001 |
3553 reflections | Δρmax = 0.20 e Å−3 |
199 parameters | Δρmin = −0.22 e Å−3 |
0 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0104 (13) |
Crystal data top
C17H24O4 | V = 3108.38 (12) Å3 |
Mr = 292.36 | Z = 8 |
Orthorhombic, Pccn | Mo Kα radiation |
a = 18.8968 (4) Å | µ = 0.09 mm−1 |
b = 18.8989 (4) Å | T = 120 K |
c = 8.7038 (2) Å | 0.22 × 0.20 × 0.10 mm |
Data collection top
Nonius KappaCCD diffractometer | 3552 independent reflections |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | 2991 reflections with I > 2σ(I) |
Tmin = 0.973, Tmax = 0.991 | Rint = 0.080 |
22526 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.116 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.20 e Å−3 |
3553 reflections | Δρmin = −0.22 e Å−3 |
199 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
O12 | 0.82227 (7) | 0.37084 (8) | 0.05384 (19) | 0.0267 (4) | |
O16 | 0.60706 (8) | 0.24787 (9) | 0.0998 (2) | 0.0311 (4) | |
O22 | 0.37273 (8) | 0.32308 (8) | 0.0600 (2) | 0.0297 (4) | |
O26 | 0.24828 (8) | 0.10777 (8) | 0.0809 (2) | 0.0328 (4) | |
C1 | 0.7500 | 0.2500 | 0.1933 (3) | 0.0215 (6) | |
C11 | 0.71545 (10) | 0.30849 (11) | 0.1003 (2) | 0.0207 (5) | |
C12 | 0.75209 (12) | 0.36453 (12) | 0.0430 (2) | 0.0227 (5) | |
C13 | 0.71854 (12) | 0.42409 (12) | −0.0421 (3) | 0.0243 (5) | |
C14 | 0.63961 (14) | 0.43466 (16) | −0.0039 (3) | 0.0240 (6) | |
C141 | 0.63120 (12) | 0.46509 (13) | 0.1569 (3) | 0.0300 (5) | |
C142 | 0.60627 (12) | 0.48499 (13) | −0.1213 (3) | 0.0305 (5) | |
C15 | 0.60352 (13) | 0.36177 (13) | −0.0150 (3) | 0.0249 (6) | |
C16 | 0.64091 (11) | 0.30284 (11) | 0.0678 (3) | 0.0226 (5) | |
C2 | 0.2500 | 0.2500 | 0.1851 (3) | 0.0231 (6) | |
C21 | 0.30897 (10) | 0.21603 (11) | 0.0938 (2) | 0.0220 (5) | |
C22 | 0.36689 (11) | 0.25365 (13) | 0.0441 (3) | 0.0224 (5) | |
C23 | 0.42898 (12) | 0.22030 (13) | −0.0335 (3) | 0.0250 (5) | |
C24 | 0.43625 (15) | 0.14089 (15) | 0.0001 (2) | 0.0237 (6) | |
C241 | 0.49082 (13) | 0.10933 (13) | −0.1119 (3) | 0.0324 (6) | |
C242 | 0.46207 (12) | 0.12918 (13) | 0.1656 (3) | 0.0296 (6) | |
C25 | 0.36430 (12) | 0.10614 (14) | −0.0242 (3) | 0.0258 (6) | |
C26 | 0.30390 (12) | 0.14283 (12) | 0.0548 (2) | 0.0247 (5) | |
H12 | 0.8396 | 0.3326 | 0.0854 | 0.040* | |
H22 | 0.3325 | 0.3407 | 0.0754 | 0.044* | |
H1A | 0.7864 | 0.2715 | 0.2606 | 0.026* | 0.50 |
H1B | 0.7136 | 0.2285 | 0.2606 | 0.026* | 0.50 |
H13A | 0.7234 | 0.4153 | −0.1537 | 0.029* | |
H13B | 0.7444 | 0.4683 | −0.0180 | 0.029* | |
H14A | 0.5809 | 0.4731 | 0.1782 | 0.045* | |
H14B | 0.6569 | 0.5100 | 0.1640 | 0.045* | |
H14C | 0.6504 | 0.4317 | 0.2323 | 0.045* | |
H14D | 0.5555 | 0.4896 | −0.1003 | 0.046* | |
H14E | 0.6131 | 0.4660 | −0.2251 | 0.046* | |
H14F | 0.6288 | 0.5315 | −0.1137 | 0.046* | |
H15A | 0.5550 | 0.3659 | 0.0268 | 0.030* | |
H15B | 0.5994 | 0.3488 | −0.1249 | 0.030* | |
H2A | 0.2711 | 0.2866 | 0.2525 | 0.028* | 0.50 |
H2B | 0.2289 | 0.2134 | 0.2525 | 0.028* | 0.50 |
H23A | 0.4727 | 0.2447 | 0.0003 | 0.030* | |
H23B | 0.4245 | 0.2272 | −0.1458 | 0.030* | |
H24A | 0.4957 | 0.0585 | −0.0923 | 0.049* | |
H24B | 0.5366 | 0.1326 | −0.0969 | 0.049* | |
H24C | 0.4748 | 0.1168 | −0.2178 | 0.049* | |
H24D | 0.4259 | 0.1459 | 0.2378 | 0.044* | |
H24E | 0.5061 | 0.1556 | 0.1821 | 0.044* | |
H24F | 0.4707 | 0.0786 | 0.1824 | 0.044* | |
H25A | 0.3543 | 0.1045 | −0.1359 | 0.031* | |
H25B | 0.3667 | 0.0567 | 0.0132 | 0.031* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O12 | 0.0179 (8) | 0.0255 (9) | 0.0369 (10) | −0.0008 (6) | 0.0006 (7) | −0.0021 (7) |
O16 | 0.0196 (8) | 0.0258 (9) | 0.0479 (10) | −0.0016 (6) | 0.0034 (7) | 0.0055 (7) |
O22 | 0.0229 (8) | 0.0219 (9) | 0.0442 (10) | −0.0014 (6) | −0.0028 (8) | −0.0014 (8) |
O26 | 0.0220 (9) | 0.0245 (9) | 0.0520 (12) | −0.0038 (6) | 0.0034 (7) | 0.0017 (7) |
C1 | 0.0196 (15) | 0.0243 (16) | 0.0206 (14) | 0.0015 (11) | 0.000 | 0.000 |
C11 | 0.0202 (11) | 0.0224 (12) | 0.0194 (10) | 0.0012 (8) | 0.0006 (8) | −0.0028 (8) |
C12 | 0.0199 (11) | 0.0270 (12) | 0.0211 (10) | 0.0015 (8) | −0.0007 (9) | −0.0039 (9) |
C13 | 0.0249 (12) | 0.0226 (12) | 0.0252 (11) | −0.0012 (9) | 0.0027 (9) | 0.0003 (10) |
C14 | 0.0235 (16) | 0.0216 (17) | 0.0269 (12) | 0.0017 (11) | 0.0005 (8) | 0.0008 (8) |
C141 | 0.0262 (12) | 0.0283 (13) | 0.0355 (13) | 0.0026 (9) | 0.0030 (9) | −0.0036 (10) |
C142 | 0.0299 (13) | 0.0260 (13) | 0.0358 (12) | 0.0015 (9) | −0.0032 (10) | 0.0063 (10) |
C15 | 0.0189 (12) | 0.0252 (14) | 0.0306 (12) | 0.0002 (10) | −0.0025 (9) | 0.0017 (9) |
C16 | 0.0209 (11) | 0.0233 (12) | 0.0235 (11) | −0.0010 (8) | 0.0019 (8) | −0.0002 (8) |
C2 | 0.0245 (15) | 0.0239 (16) | 0.0209 (15) | 0.0018 (11) | 0.000 | 0.000 |
C21 | 0.0193 (11) | 0.0238 (12) | 0.0228 (11) | 0.0012 (8) | −0.0013 (8) | 0.0021 (8) |
C22 | 0.0191 (11) | 0.0211 (12) | 0.0271 (12) | −0.0006 (8) | −0.0065 (9) | 0.0037 (10) |
C23 | 0.0213 (11) | 0.0256 (13) | 0.0281 (12) | −0.0015 (9) | 0.0015 (9) | 0.0014 (10) |
C24 | 0.0217 (16) | 0.0209 (15) | 0.0286 (12) | −0.0014 (11) | −0.0010 (8) | −0.0002 (8) |
C241 | 0.0281 (13) | 0.0322 (13) | 0.0368 (14) | 0.0032 (9) | 0.0022 (10) | −0.0034 (10) |
C242 | 0.0267 (12) | 0.0306 (13) | 0.0315 (12) | 0.0012 (10) | −0.0047 (9) | 0.0047 (9) |
C25 | 0.0210 (13) | 0.0246 (14) | 0.0319 (13) | 0.0003 (10) | 0.0002 (9) | −0.0011 (9) |
C26 | 0.0199 (11) | 0.0275 (12) | 0.0268 (11) | −0.0015 (9) | −0.0022 (8) | 0.0041 (9) |
Geometric parameters (Å, º) top
O12—C12 | 1.335 (3) | C142—H14E | 0.98 |
C12—C11 | 1.360 (3) | C142—H14F | 0.98 |
C11—C16 | 1.441 (3) | C15—C16 | 1.503 (3) |
C16—O16 | 1.251 (3) | C15—H15A | 0.99 |
O12—H12 | 0.84 | C15—H15B | 0.99 |
O22—C22 | 1.324 (3) | C2—C21 | 1.512 (2) |
C22—C21 | 1.375 (3) | C2—C21ii | 1.512 (2) |
C21—C26 | 1.428 (3) | C2—H2A | 0.99 |
C26—O26 | 1.263 (3) | C2—H2B | 0.99 |
O22—H22 | 0.84 | C22—C23 | 1.493 (3) |
C1—C11i | 1.518 (2) | C23—C24 | 1.535 (4) |
C1—C11 | 1.518 (2) | C23—H23A | 0.99 |
C1—H1A | 0.99 | C23—H23B | 0.99 |
C1—H1B | 0.99 | C24—C25 | 1.525 (4) |
C12—C13 | 1.489 (3) | C24—C242 | 1.537 (3) |
C13—C14 | 1.541 (4) | C24—C241 | 1.539 (3) |
C13—H13A | 0.99 | C241—H24A | 0.98 |
C13—H13B | 0.99 | C241—H24B | 0.98 |
C14—C141 | 1.522 (3) | C241—H24C | 0.98 |
C14—C142 | 1.532 (4) | C242—H24D | 0.98 |
C14—C15 | 1.540 (4) | C242—H24E | 0.98 |
C141—H14A | 0.98 | C242—H24F | 0.98 |
C141—H14B | 0.98 | C25—C26 | 1.502 (3) |
C141—H14C | 0.98 | C25—H25A | 0.99 |
C142—H14D | 0.98 | C25—H25B | 0.99 |
| | | |
C12—O12—H12 | 109.5 | C11—C16—C15 | 119.93 (19) |
C22—O22—H22 | 109.5 | C21—C2—C21ii | 116.6 (2) |
C11i—C1—C11 | 115.6 (2) | C21—C2—H2A | 108.1 |
C11i—C1—H1A | 108.4 | C21ii—C2—H2A | 108.1 |
C11—C1—H1A | 108.4 | C21—C2—H2B | 108.1 |
C11i—C1—H1B | 108.4 | C21ii—C2—H2B | 108.1 |
C11—C1—H1B | 108.4 | H2A—C2—H2B | 107.3 |
H1A—C1—H1B | 107.5 | C22—C21—C26 | 118.7 (2) |
C12—C11—C16 | 118.92 (19) | C22—C21—C2 | 122.18 (18) |
C12—C11—C1 | 122.93 (17) | C26—C21—C2 | 119.15 (16) |
C16—C11—C1 | 118.13 (16) | O22—C22—C21 | 123.1 (2) |
O12—C12—C11 | 123.3 (2) | O22—C22—C23 | 113.6 (2) |
O12—C12—C13 | 112.98 (19) | C21—C22—C23 | 123.3 (2) |
C11—C12—C13 | 123.6 (2) | C22—C23—C24 | 113.37 (19) |
C12—C13—C14 | 113.76 (19) | C22—C23—H23A | 108.9 |
C12—C13—H13A | 108.8 | C24—C23—H23A | 108.9 |
C14—C13—H13A | 108.8 | C22—C23—H23B | 108.9 |
C12—C13—H13B | 108.8 | C24—C23—H23B | 108.9 |
C14—C13—H13B | 108.8 | H23A—C23—H23B | 107.7 |
H13A—C13—H13B | 107.7 | C25—C24—C23 | 108.3 (2) |
C141—C14—C142 | 109.6 (2) | C25—C24—C242 | 110.6 (2) |
C141—C14—C15 | 110.5 (2) | C23—C24—C242 | 110.3 (2) |
C142—C14—C15 | 109.4 (2) | C25—C24—C241 | 110.0 (2) |
C141—C14—C13 | 110.37 (19) | C23—C24—C241 | 108.6 (2) |
C142—C14—C13 | 109.57 (19) | C242—C24—C241 | 109.0 (2) |
C15—C14—C13 | 107.4 (2) | C24—C241—H24A | 109.5 |
C14—C141—H14A | 109.5 | C24—C241—H24B | 109.5 |
C14—C141—H14B | 109.5 | H24A—C241—H24B | 109.5 |
H14A—C141—H14B | 109.5 | C24—C241—H24C | 109.5 |
C14—C141—H14C | 109.5 | H24A—C241—H24C | 109.5 |
H14A—C141—H14C | 109.5 | H24B—C241—H24C | 109.5 |
H14B—C141—H14C | 109.5 | C24—C242—H24D | 109.5 |
C14—C142—H14D | 109.5 | C24—C242—H24E | 109.5 |
C14—C142—H14E | 109.5 | H24D—C242—H24E | 109.5 |
H14D—C142—H14E | 109.5 | C24—C242—H24F | 109.5 |
C14—C142—H14F | 109.5 | H24D—C242—H24F | 109.5 |
H14D—C142—H14F | 109.5 | H24E—C242—H24F | 109.5 |
H14E—C142—H14F | 109.5 | C26—C25—C24 | 114.5 (2) |
C16—C15—C14 | 115.11 (19) | C26—C25—H25A | 108.6 |
C16—C15—H15A | 108.5 | C24—C25—H25A | 108.6 |
C14—C15—H15A | 108.5 | C26—C25—H25B | 108.6 |
C16—C15—H15B | 108.5 | C24—C25—H25B | 108.6 |
C14—C15—H15B | 108.5 | H25A—C25—H25B | 107.6 |
H15A—C15—H15B | 107.5 | O26—C26—C21 | 121.4 (2) |
O16—C16—C11 | 121.16 (19) | O26—C26—C25 | 118.2 (2) |
O16—C16—C15 | 118.79 (18) | C21—C26—C25 | 120.4 (2) |
| | | |
C1—C11—C12—O12 | 4.8 (3) | C26—C21—C22—O22 | 172.5 (2) |
C1—C11—C16—O16 | −7.9 (3) | C2—C21—C22—O22 | −6.2 (3) |
C11i—C1—C11—C12 | −83.8 (2) | C2—C21—C26—O26 | 7.4 (3) |
C11i—C1—C11—C16 | 94.2 (2) | C21ii—C2—C21—C22 | 87.2 (2) |
C16—C11—C12—O12 | −173.2 (2) | C21ii—C2—C21—C26 | −91.4 (2) |
C16—C11—C12—C13 | 5.0 (3) | C26—C21—C22—C23 | −7.2 (3) |
C1—C11—C12—C13 | −177.01 (19) | C2—C21—C22—C23 | 174.2 (2) |
O12—C12—C13—C14 | −157.34 (19) | O22—C22—C23—C24 | 158.53 (19) |
C11—C12—C13—C14 | 24.3 (3) | C21—C22—C23—C24 | −21.8 (3) |
C12—C13—C14—C141 | 71.8 (3) | C22—C23—C24—C25 | 48.2 (3) |
C12—C13—C14—C142 | −167.4 (2) | C22—C23—C24—C242 | −73.0 (3) |
C12—C13—C14—C15 | −48.7 (2) | C22—C23—C24—C241 | 167.7 (2) |
C141—C14—C15—C16 | −72.1 (3) | C23—C24—C25—C26 | −49.4 (3) |
C142—C14—C15—C16 | 167.1 (2) | C242—C24—C25—C26 | 71.7 (3) |
C13—C14—C15—C16 | 48.3 (3) | C241—C24—C25—C26 | −167.9 (2) |
C12—C11—C16—O16 | 170.2 (2) | C22—C21—C26—O26 | −171.3 (2) |
C12—C11—C16—C15 | −5.8 (3) | C22—C21—C26—C25 | 6.4 (3) |
C1—C11—C16—C15 | 176.1 (2) | C2—C21—C26—C25 | −174.9 (2) |
C14—C15—C16—O16 | 161.0 (2) | C24—C25—C26—O26 | −158.7 (2) |
C14—C15—C16—C11 | −22.8 (3) | C24—C25—C26—C21 | 23.5 (3) |
Symmetry codes: (i) −x+3/2, −y+1/2, z; (ii) −x+1/2, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O12—H12···O16i | 0.84 | 1.83 | 2.642 (2) | 162 |
O22—H22···O26ii | 0.84 | 1.81 | 2.640 (2) | 168 |
Symmetry codes: (i) −x+3/2, −y+1/2, z; (ii) −x+1/2, −y+1/2, z. |
Experimental details
Crystal data |
Chemical formula | C17H24O4 |
Mr | 292.36 |
Crystal system, space group | Orthorhombic, Pccn |
Temperature (K) | 120 |
a, b, c (Å) | 18.8968 (4), 18.8989 (4), 8.7038 (2) |
V (Å3) | 3108.38 (12) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.22 × 0.20 × 0.10 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.973, 0.991 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22526, 3552, 2991 |
Rint | 0.080 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.116, 1.03 |
No. of reflections | 3553 |
No. of parameters | 199 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.22 |
Selected geometric parameters (Å, º) topO12—C12 | 1.335 (3) | O22—C22 | 1.324 (3) |
C12—C11 | 1.360 (3) | C22—C21 | 1.375 (3) |
C11—C16 | 1.441 (3) | C21—C26 | 1.428 (3) |
C16—O16 | 1.251 (3) | C26—O26 | 1.263 (3) |
| | | |
C1—C11—C12—O12 | 4.8 (3) | C2—C21—C22—O22 | −6.2 (3) |
C1—C11—C16—O16 | −7.9 (3) | C2—C21—C26—O26 | 7.4 (3) |
C11i—C1—C11—C12 | −83.8 (2) | C21ii—C2—C21—C22 | 87.2 (2) |
C11i—C1—C11—C16 | 94.2 (2) | C21ii—C2—C21—C26 | −91.4 (2) |
Symmetry codes: (i) −x+3/2, −y+1/2, z; (ii) −x+1/2, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O12—H12···O16i | 0.84 | 1.83 | 2.642 (2) | 162 |
O22—H22···O26ii | 0.84 | 1.81 | 2.640 (2) | 168 |
Symmetry codes: (i) −x+3/2, −y+1/2, z; (ii) −x+1/2, −y+1/2, z. |
The structure of 2,2'-methylenebis(3-hydroxy-2-cyclohexen-1-one), (I), has recently been the subject of a brief report (SethuSankar et al., 2000), although the molecular constitution is incorrectly depicted in that report. This compound crystallizes in space group Pbca with Z' = 1, and the molecular structure is characterized by two rather short intramolecular hydrogen bonds.
We report here the structure of a tetramethyl analogue of (I), namely 2,2'-methylenebis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one), (II), originally obtained in low yield as an unexpected by-product in a three-component reaction between 2-methoxy 4-aminopyrimidin-6(1H)-one, formaldehyde and 5,5-dimethylcyclohexane-1,3-dione (dimedone), which had been intended to produce a tricyclic octahydropyrimido[3,4-b]quinoline system. Compound (II) was subsequently obtained in ca 70% yield by reaction of dimedone with aqueous formaldehyde in a reaction analogous to that used for the synthesis of compound (I) (SethuSankar et al., 2000). Compound (II) crystallizes in the orthorhombic space group Pccn; there are two independent molecules in the cell, each lying across a twofold rotation axis, so that Z' = 2 × 0.5 = 1. In the selected asymmetric unit, molecule 1 containing C1 (Fig. 1a) lies across the axis along (3/4, 1/4, z), while molecule 2 containing C2 (Fig. 1 b) lies across the axis (1/4, 1/4, z). The metric unit cell very closely mimics a tetragonal cell with the a and b repeat vectors differing by only ca 0.002 Å. However, the refined structure is clearly orthorhombic, although subject to twinning across the (110) plane; a search for possible additional symmetry revealed none, and the arrangement of the molecules in the unit cell (Fig. 2) clearly rules out the possibility of any kind of fourfold axis.
The two independent molecules are both chiral, with molecular symmetry C2, but the space group ensures that for each there are equal numbers of the two enantiomorphs present in the crystal. The two molecules in the selected asymmetric unit are in fact of opposite hand, as shown qualitatively by their overall configurations (Fig. 1) and quantitatively both by the key torsion angles (Table 1) and, better, by the ring-puckering parameters. For the independent rings C11–C16 and C21–C26, the overall puckering amplitudes Q (Cremer & Pople, 1975) are identical within experimental uncertainty, viz. 0.457 (3) and 0.459 (3) Å, respectively, but for the atom sequences Cn1 to Cn6 (n = 1 or 2), the θ values are 59.0 (3) and 119.8 (3)°, respectively, and the supplementary nature of these values defines different absolute configurations for the two molecules (Boeyens, 1978). The ϕ values, based on the same atom sequences for the rings C11–C16 and C21–C26, are 178.5 (4) and 0.9 (6)°, respectively, and the ring-puckering parameters taken together indicate a sofa or envelope conformation as the best single qualitative descriptor, with local pseudo-mirror planes in each ring, passing through the atoms Cn1 and Cn4.
Within the molecules, the C—C and C—O distances within the On2—Cn2—Cn1—Cn6—On6 (n = 1 or 2) fragments are clearly indicative of alternating single and double bonds, and they are consistent with the location of the associated H atoms, as located from difference maps. The remaining bond distances and angles show no unusual values. In each molecule, there are two fairly short O—H···O hydrogen bonds (Table 2), which probably play a role in controlling the overall molecular conformation, in particular, in constraining the molecules to have overall twofold rotational symmetry.
There are, however, no direction-specific interactions between the molecules of (II). In particular, there are no C—H···O hydrogen bonds; the shortest intermolecular H···O contact distance is not significantly less than the the sum of the van der Waals radii. In compound (I), a number of intermolecular C—H···O contacts were reported as hydrogen bonds (SethuSankar et al., 2000), but in every case the H···O distance exceeds 2.55 Å (the overall range reported was 2.56–2.71 Å), so that it is doubtful if these contacts are structurally significant.