1-(2-Hydroxy-5-(1-methoxyethyl)phenyl)-3-methylbut-2-en-1-one (1)
1-(2-Hydroxy-5-methoxyphenyl)-3-methylbut-2-en-1-one (2)
Journal of the Brazilian Chemical Society
Print version ISSN 0103-5053
J. Braz. Chem. Soc. vol.22 no.12 São Paulo Dec. 2011
http://dx.doi.org/10.1590/S0103-50532011001200021
http://www.scielo.br/scielo.php?pid=S0103-50532011001200021&script=sci_arttext
1-(2-Hydroxy-5-(1-methoxyethyl)phenyl)-3-methylbut-2-en-1-one (1)
Yellow crystal; UV (MeOH) λmax/nm (log ε): 220 (4.04), 274 (4.13), 344 (3.56); IR (KBr) νmax/cm-1: 3436 (OH), 1638 (C=O), 1580 (o-hidroxyacetone), 1486 (Ar); DIMS m/z (relative intensity): 256.9 [M + Na]+ (100), 235.0 [M + H]+ (10) in positive mode and 232.8 [M - H]- (100) in negative mode (calc. for C14H18O3: 234.0); for 1H and 13C NMR spectroscopic data, see Table 1.
1-(2-Hydroxy-5-methoxyphenyl)-3-methylbut-2-en-1-one (2)
Yellow oil; UV (MeOH) λmax/nm (log ε): 220 (4.04), 272 (4.08), 372 (3.58); IR (KBr) νmax/cm-1: 3513 (OH), 1643 (C=O), 1585 (o-hidroxyacetone), 1488 cm-1 (Ar); DIMS m/z (relative intensity): 228.9 [M + Na]+ (100), 206.9 [M + H]+ (10) in positive mode and 204.8 [M - H]- (100) in negative mode (calc. for C12H14O3: 206,24); for 1H and 13C NMR spectroscopic data, see Table 1.
Structural elucidation
1-(2-Hydroxy-5-(1-methoxyethyl)phenyl)-3-methylbut-2-en-1-one (1)
The DIMS spectrum showed a quasi-molecular ion peak at m/z 235 and 233 in [M + H]+ and [M - H]- mode, respectively, corresponding to a molecular weight of 234 m/z, compatible with the molecular formula C14H18O3.
The 1H NMR (Table 1) and homonuclear correlation spectroscopy (COSY) NMR spectra showed the presence of an AB system at δ 7.5 (d, J 2.0 Hz, H-3), 7.2 (dd, J 8.6 and 2.0 Hz, H-5) and 6.80 (d, J 8.6 Hz, H-6); a vinyl hydrogen at δ 6.6 ppm (s, H-10); a methoxyl at δ 3.15 (s); two singlet at chemical shift 2.15 (H-13) and 1.99 (H-12), indicative of methyl groups in a isoprene system, and another methyl group at δ 1.2 ppm (d, J 6,3 Hz, H-8) coupled in COSY NMR to a methine signal at δ 4.2 (q, J 6.3 Hz, H-7). The 13C NMR spectrum (Table 1) showed four signals corresponding to CH3 group with chemical shifts δ 56.0, 29.0, 25.2 and 22.5. The one corresponds to a methoxyl group as substituent at C-7, the third to methyl in C-8, finally, the second and four correspond to two methyl groups on double bond of isoprene system C-12 and C-13. The signal at δ 196.2 ppm was attributed to the carbonyl carbon, the signals δ 164.74, 134.3, 133.9, 127.7, 120.8 and 118.9 correspond to a six aromatic carbon atoms in a benzene ring. Besides this, the structure was elucidated with the help of 2D NMR techniques: heteronuclear single-quantum correlation spectroscopy (HMQC) and heteronuclear multiple-bond correlation spectroscopy (HMBC). The HMBC experiment showed correlations of C-1 (δ 164.74) with H-3 (δ7.5) and H-5 (δ 7.2); C-2 (δ 120.8) with H-6 (δ 6.80) and H-3 (δ 7.5), similarly, H-7 (δ 4.2) correlates with the C-4 (δ 133.9) and C-5 (δ 134.3). The position of de quaternary carbon C-4 was obtained through HMBC correlation with the CH3 at (δ 1.2).
1-(2-Hydroxy-5-methoxyphenyl)-3-methylbut-2-en-1-one (2)
Comparing the spectroscopic data of the compound 1 and 2 and the literature,18,22,23 it was possible to determine the structure of the second, with some differences between both. In the compound 2, the methoxyl group is bonded directly to aromatic ring C-4, that way, this carbon showed a higher chemical shift, C-4 (δ152.2), affecting the C-3 with δ 113.3. The other difference was the absence of carbons C-7 and C-8. The structures are showed in Figure 1.
Figure S15 - Click to enlarge
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