Ethynylphenols
1235
1695, 1610, 1460, 1370, 1350 (m), 1270, 1165, 995, 905, 765.
Anal. Calc. for C11H9NO3: C 65.03, H 4.46, N 6.89. Found: C
65.02, H 4.32, N 6.81 %.
2,4-Dimethoxyphenylacetylene 11d
Compound 9c (200 mg) was sublimed into the FVP apparatus at
170–1808C and pyrolyzed at 7508C and 10ꢁ3 hPa. The products
were isolated in a liquid-N2 cold trap. After the end of the
experiment, the CO2 and acetonitrile were removed under
vacuum, leaving 80 mg (84 %) of crude 11c, which was purified
by column chromatography (silica gel, CHCl3). The first frac-
tion afforded 11c as an oil (50 mg, 52 %). dH (DMSO-d6) 7.4 (d,
J 9, 1H), 6.5 (m, 1H), 6.4 (d, J 2, 1H), 4.0 (s, 1H), 3.9 (s, 3H), 3.8
(s, 3H). nmax (KBr)/cmꢁ1 3280, 2960, 2100, 1601, 1570, 1405,
1275, 1200, 810. m/z (EI) 162 (Mþ, 100 %), 119 (15), 91 (11),
65 (10). HRMS m/z 162.0670; calcd for C10H10O2 162.0681.
The properties were in agreement with literature data.[21]
4-(2,4-Dimethoxyphenylmethylidene)-3-methylisoxazol-
5(4H)-one 10d
This compound was prepared in the same manner as 10a from
2,4-dimethoxybenzaldehyde (1.66 g, 0.01 mol) to afford a yield
of 1.00 g (40 %), mp 2588C. dH (DMSO-d6) 8.2 (s, 1H), 7.1–6.9
(m, 3H), 3.9 (s, 3H), 4.0 (s 3H), 2.3 (s, 3H). nmax (KBr)/cmꢁ1
2850, 1730, 1580, 1550, 1320, 1270, 1205, 860, 820, 760, 730.
m/z (EI) 247 (Mþ, 100 %), 216 (37), 177 (56), 173 (10), 162 (23),
147 (13), 119 (14). Anal. Calc. for C13H13NO4: C 63.16, H 5.30,
N 5.66. Found: C 63.20, H 5.41, N 5.64 %.
Supplementary Material
Scheme S1 showing the potential cyclization of 1-buten-3-yn-1-
ols to furans under FVP conditions is available on the Journal’s
website.
m-Ethynylphenol 11a
Compound 10a (161 mg, 0.79 mmol) was sublimed into the FVP
apparatus at 170–1808C and pyrolyzed at 8008C and 10ꢁ3 hPa.
The products were isolated in a liquid-N2 cold trap. After the end
of the experiment, the CO2 and acetonitrile were removed under
vacuum, and the remaining light-yellow, liquid product was
distilled at 508C and 1 hPa to yield 81 mg (87 %) of 10a as a
colourless liquid. dH (DMSO-d6) 7.2–6.7 (m, 4H), 4.90 (br s, 1H,
OH), 3.05 (s, 1H). nmax (KBr)/cmꢁ1 3600–3000 (br), 3280,
2090, 1565–1610, 1465, 1430, 1135, 850, 770, 675. m/z (EI) 118
(Mþ, 100 %), 89 (18), 63 (10). HRMS m/z 118.0420; calcd for
C8H6O 118.0419. The properties are in agreement with litera-
ture data.[10,12]
Acknowledgement
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and The University of Queensland.
References
[1] C. Wentrup, J. Becker, H.-W. Winter, Angew. Chem. Int. Ed. 2015, 54,
[2] C. Wentrup, H.-W. Winter, D. Kvaskoff, J. Phys. Chem. A 2015, 119.
[3] (a) Acetylenes in synthesis: Science of Synthesis: Houben-Weyl
Methods of Molecular Transformations (Ed. H. Hopf) 2008, Vol. 43
(Thieme: Stuttgart).
p-Ethynylphenol 11b
(b) I. V. Alabugin, B. Gold, J. Org. Chem. 2013, 78, 7777. doi:10.1021/
(c) In materials science: E. Chernick, R. Tykwinski, J. Phys. Org.
(d) In click chemistry: H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew.
(e) M. Meldal, C. W. Tornøe, Chem. Rev. 2008, 108, 2952.
Compound 10b (300 mg) was sublimed into the FVP apparatus
at 150–1608C and pyrolyzed at 8008C and 10ꢁ3 hPa. The pro-
ducts were isolated in a liquid-N2 cold trap. After the end of the
experiment, the CO2 and acetonitrile were removed under
vacuum at ꢁ408C, and the remaining brown, crystalline product
was sublimed at 258C and 10ꢁ1 hPa to yield 117 mg (67 %) of
11b as a white solid, mp 56–588C. dH (DMSO-d6) 7.45 (d, 2H,
J 9), 6.80 (d, 2H, J 9), 4.85 (br s, 1H, OH), 3.01 (s, 1H).
nmax (KBr)/cmꢁ1 3400–3200 (br), 3270, 2097, 1610, 1590,
1500, 1440, 1225, 830, 820, 680. m/z (EI) 118 (Mþ, 100 %), 89
(22), 63 (11). HRMS m/z 118.0417; calcd for C8H6O 118.0419.
The properties were in agreement with literature data.[11,12]
(f) J. E. Moses, A. D. Moorhouse, Chem. Soc. Rev. 2007, 36, 1249.
(g) M. G. Finn, V. V. Fokin, Chem. Soc. Rev. 2010, 39, 1231 and
[4] C. Wentrup, H.-W. Winter, Angew. Chem. Int. Ed. Engl. 1978, 17, 609.
[5] C. Wentrup, W. Reichen, Helv. Chim. Acta 1976, 59, 2615.
o-Ethynylphenol 11c and Benzofuran 12
[6] H. S. Rzepa, C. Wentrup, J. Org. Chem. 2013, 78, 7565. doi:10.1021/
[7] I. D. Mackie, R. P. Johnson, J. Org. Chem. 2009, 74, 499. doi:10.1021/
[8] (a) H.-W. Winter, C. Wentrup, Angew. Chem. Int. Ed. Engl. 1980, 19,
(a) Compound 10c (150 mg) was sublimed into the FVP appa-
ratus at 1408C and pyrolyzed at 8008C and 10ꢁ3 hPa. The pro-
ducts were isolated in a liquid-N2 cold trap. After the end of the
experiment, the CO2 and acetonitrile were removed under
vacuum at ꢁ408C, and the remaining yellow-brown oil was
distilled bulb to bulb to yield a ,1 : 2 mixture of 11c and 12.
Data for 11c: dH (CDCl3) 7.4 (m, 1H), 7.3 (m, 1H), 7.0
(m, 1H), 6.8 (m, 1H), 5.9 (s, 1H, OH), 3.5 (s, 1H, CC–H).
nmax (KBr)/cmꢁ1 3400 (br, OH), 2120 (vw, CCH), 1535 (w),
1340 (m), 1200 (w), 1150 (w), 940 (s), 830 (s), 810 (s). The
properties were in agreement with literature data[12,19]
(b) C. Wentrup, H. Briehl, P. Lorencak, U. J. Vogelbacher, H.-W.
Winter, A. Maquestiau, R. Flammang, J. Am. Chem. Soc. 1988, 110,
[10] F. Bohlmann, K.-D. Albrecht, G. Schmidt, Chem. Ber. 1966, 99, 2822.
[11] I. L. Kotlyarevskii, M. I. Bardamova, Izvest. Akad. Nauk SSSR, Ser.
(b) Compound 10c was subjected to FVP at 10008C. The IR
and 1H NMR spectra of the product indicated that it was almost
pure benzofuran 12 containing very little o-ethynylphenol 11c.
Benzofuran 12 was identified by comparison of IR and NMR[20]
spectra with those of an authentic sample.
Khim. 1964, 11, 2073.
[12] T. Pirali, S. Gatti, R. Di Brisco, S. Tacchi, R. Zaninetti, E. Brunelli,
A. Massarotti, G. Sorba, P. L. Canonico, L. Moro, A. A. Genazzani,
G. C. Tron, R. A. Billington, ChemMedChem 2007, 2, 437. The IR
spectra of 2-, 3-, and 4-ethynylphenols reported by these authors cannot