March 1998
SYNTHESIS
303
2,2-Dimethyl-3,4-dihydro-2H-1-benzopyran (3e): yellow oil; yield:
6.5 g (80%; selectivity: 90%); bp 55–58 °C/0.05 Torr (lit.6 bp 67–
68 °C/2 Torr).
(1) Clark, J. H.; Macquarrie, D. J. Chem. Soc. Rev. 1996, 303.
Espeel, P, H.; Janssens, B.; Jacobs, P. A. J. Org. Chem. 1993,
58, 7688.
6-Hydroxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (3f): white
solid; yield: 4.5 g (50%; selectivity: 75%); mp 77–78 °C.
IR (KBr): n = 3209 (OH) cm–1.
Hölderich, W. F.; Heitmann, G, Catal. Today 1997, 353.
(2) Hölderich, W. F.; van Bekkum, H. Stud. Surf. Sci. Catal. 1991,
58, 631.
1H NMR (CDCl3, 300 MHz): d = 1.30 (s, 6H, 2CH3), 1.75 (t, 2H, J =
6.8 Hz, CH2), 2.68 (t, 2H, J = 6.8 Hz, CH2 [position 4]), 5.7 (br s, 1H,
OH), 6.54 (d, 1H, J = 2.9 Hz, H-5), 6.57 (dd, 1H, J = 8.6 and 2.9 Hz,
H-7), 6.64 (d, 1H, J = 8.6 Hz, H-8).
Balogh, M.; Laszlo, P. Organic Chemistry using Clays; Sprin-
ger Verlag: New York, 1993.
Comprehensive Supramolecular Chemistry; Alberti, G.; Bein,
T. Eds.; Pergamon: UK, 1996; Vol. 7.
Meurig Thomas, J. Angew. Chem., Int. Ed. Engl. 1994, 33, 913.
Ramoa Ribeiro, F.; Alvarez, F.; Henriquez, C.; Lemos, F.; Lo-
pes, J. M.; Ribeiro, M. F. J. Mol. Catal. A: Chemical 1995, 96,
245.
MS: m/z (%) = 178 (M+, 52), 163 (24), 123 (100).
C11H14O2
(178.23)
calcd
found
C
74.13
74.20
H
7.92
8.00
Barthomeuf, D. Catal. Rev. 1996, 38, 521.
(3) See, for example: Climent, M. J.; Corma, A.; Iborra, S.; Primo,
J. J. Catal. 1995, 151, 60.
6-Hydroxy-2,2,5,7,8-pentamethyl-3,4-dihydro-2H-1-benzopyran
(3g): red oil; yield: 7.2 g (65%; selectivity: 85%); bp 77–80°C/0.05
Torr.
IR (KBr): n = 3451 (OH) cm–1.
Martens, J. A.; Souverijns, W.; Verrelst, W.; Parton, R.; Fro-
ment, G. F.; Jacobs, P. A. Angew. Chem., Int. Ed. Engl. 1995,
34, 2528.
Hoefnagel, A. J.; Gunnewegh, E. A.; Downing, R. S.; van Bek-
kum, H. J. Chem. Soc., Chem. Commun. 1995, 225.
Armengol, E.; Cano, M. L.; Corma, A.; Garcia, H.; Navarro, M.
T. J. Chem. Soc„ Chem. Commun. 1995, 519.
1H NMR (CDCl3, 300 MHz): d = 1.28 (s, 6H, 2 CH3), 1.78 (t, 2H, J
= 6.9 Hz, CH2), 2. 11 (s, 6H, 2 CH3-Ar), 2.15 (s, 3H, CH3-Ar), 2.61 (t,
2H, J = 6.9 Hz, CH2), 4.2 (br s, 1H, OH).
MS: m/z (%) = 220 (M+, 70), 164 (100).
C14H20O2
(220.31)
calcd
found
C
6.33
76.51
H
9.15
9.03
Arienti, A.; Bigi, F.; Maggi, R.; Marzi, E.; Moggi, P.; Rastelli,
M.; Sartori. G., Tarantola, F. Tetrahedron 1997, 53, 3795.
Arienti, A.; Bigi, F.; Maggi, R.; Moggi, P.; Rastelli, M.; Sartori.
G.; Trere, A. J. Chem. Soc., Perkin Trans. 1 1997, 1391.
(4) Bigi, F.; Carloni, S.; Maggi, R.; Muchetti, C.; Sartori, G. J. Org.
Chem. 1997, 162, 7024.
(5) Schweizer, E. E.; Meeder-Nycz, D. In Heterocyclic Com-
pounds. Chromenes, Chromanones and Chromanes; Ellis, G. P.
Ed.; Wiley: Chichester, 1977; pp 11–139.
6-Chloro-2,2-dimethyl-3,4dihydro-2H-1-benzopyran (3h): yellow
oil; yield: 2.9 g (40%; selectivity: 80%); bp 83–85 °C/0.05 Torr (lit.6
bp 94–95 °C/1 Torr).
Synthesis of o-Isopentenylphenols 4; General Procedure:
The reactions were carried out as described in General Procedure for
the chromans 3 reducing the reaction temperature from 120°C to
80°C. Compounds 4 are accompanied by the corresponding aryl iso-
pentenyl ethers (3–5%).
Glüsenkamp, K.-H.; Büchi, G. J. Org. Chem. 1986, 51, 4481.
Dauben, W. G.; Cogen, J. M.; Behar, V. Tetrahedron Lett. 1990,
31, 3241.
4-Methoxy-2-(3-methylbut-2-enyl)phenol (4a): yellow oil; yield:
4.3 g (45%; selectivity: 80%); bp 48–51 °C/0.1 Torr.
Marsui, M.; Yamamoto, H. Bull. Chem. Soc. Jpn 1996, 69, 137.
Ishihara, K.; Kubota, M.; Yamamoto, H. Synlett 1996, 1045.
(6) Bolzoni, L, ; Casiraghi, G.; Casnati, G.; Sartori, G. Angew.
Chem„ Int. Ed. Engl. 1978, 17, 684.
(7) Hosokawa, T.; Miyagi, S.; Murahashi, S.-I.; Sonoda, A. J.
Chem. Soc., Chem. Commun. 1978, 687.
Kalinin, V. N.; Shostakovsky, M. V.; Ponomaryov, A. B. Tetra-
hedron Lett. 1990, 31, 4073.
(8) Molyneux, R. J.; Jurd, L. Tetrahedron 1970, 26, 4743.
Pochini, A.; Marchelli, R.; Bocchi, V. Gazz. Chim. Ital. 1975,
105, 1253.
IR (NaCl): n = 3410 (OH) cm–1.
1H NMR (CDCl3, 300 MHz): d = 1.76 (s, 3H, CH3), 1.77 (s, 3H, CH3),
3.32 (d, 2H, J = 7.1 Hz, CH2), 3.75 (s, 3H, OCH3), 4.77 (s, 1H, OH),
5.3 (t, 1H, J = 7.1 Hz, CH), 6.64 (dd, 1H, J = 8.3 and 2.9 Hz, H-5),
6.67 (d, 1H, J = 2.9 Hz, H-3), 6.73 (d, 1H, J = 8.3 Hz, H-6).
MS: m/z (%) = 192 (M+, 81), 137 (100), 108 (26).
C12H16O2
(192.26)
calcd
found
C
74.97
75.12
H
8.39
8.45
1-(3-Methylbut-2-enyl)-2-naphthol (4b): pale brown oil; yield: 4.8 g
Laan, J. A. M.; Giesen, F. L. L.; Ward, J. P. Chem. and Ind.
(London) 1989, 354.
(45%; selectivity: 85%); bp 60–63 °C/0.1 Torr.19
(9) Zeolite HSZ-360 is a commercial (Tosoh Corp.) acid faujasitic
type catalyst with 13.9 SiO2/Al2O3 molar ratio, pore size 7.4Å,
surface area 500+10 m2/g (determined in our laboratory by
B. E. T. method: Brunauer, S.; Emmett, P. H.; Teller, E. J. Am.
Chem. Soc. 1938, 60, 309), acidity 0.51 meq. H+/g [determined
in our laboratory by temperature programmed desorption of am-
monia gas (NH3-TPD): Berteau, P.; Delmon, B. Catal. Today
1989, 5, 121] and with the following chemical composition
(wt% dry basis): SiO2 89.0, Al2O3 10.9, Na2O 0.06.
(10) By carrying out the reaction for time shorter than 6 h, a yield de-
crease of products 3 and 4 was observed; on the contrary, no
yield increase was observed by stirring the reaction mixture for
a time longer than 6 h.
2-(3-Methylbut-2-enyl)-I-naphthol (4c): pale brown oil; yield: 4.2 g
(40%; selectivity: 85%); bp 90–92 °C/0.1 Torr.19
2-(3-Methylbut-2-enyl)phenol (4e): yellow oil; yield: 2.8 g (35%; se-
lectivity: 75%); bp 53–56 °C/0.1 Torr (lit.20 bp 109–112 °C/5 Torr).
3,4,5-Trimethoxy-2-(3-methylbut-2-enyl)phenol (4i): white solid;
yield: 5.0 g (40%; selectivity: 95%); mp 89–91 °C (lit.11 mp 88–
90°C).
3,5,6-Trimethyl-2-(3-methylbut-2-enyl)-1,4-benzoquinone (5g): yel-
low oil; yield: 5.8 g (53%; selectivity: 95%); bp 84–86 °C/0.1 Torr.12
At 60 °C the yields in compounds 4 were lower. At a tempera-
ture higher than 120 °C, no yield increase in compounds 3 was
observed.
No coke or tar formation on the calalyst surface was observed
by carrying out the reaction at 120 °C for 6 h under the reported
conditions.
A reaction carried out with the used catalyst (previously washed
with acetone and heated for 6 h at 500 °C) gave a 40% yield of
chroman 3a.
The authors acknowledge the support of the Ministero dell’Univer-
sità e della Ricerca Scientifica e Tecnologica (MURST) “Progetto
Nazionale Sintesi e Reattività Organica” (ex 40%) and the Consiglio
Nazionale delle Ricerche (CNR), Italy. The authors are grateful to
the Centro Interfacoltà Misure (CIM) for the use of NMR and mass
instruments. The authors thank Mr. Pierantonio Bonaldi for techni-
cal assistance.