Alkylation of Phenol And Hydroquinone by Prenol in the Presence of Organoaluminum Catalysts

Article abstract of DOI:10.1007/s10600-018-2245-y

Prenylphenols and 2,2-dimethylbenzopyrans were synthesized via alkylation of phenol and hydroquinone with prenol in the presence of organoaluminum catalysts, i.e., aluminum phenoxide and isopropoxide. Reaction products were isolated and characterized. Sev

Full text of DOI:10.1007/s10600-018-2245-y

DOI 10.1007/s10600-018-2245-y
Chemistry of Natural Compounds, Vol. 54, No. 1, January, 2018
ALKYLATION OF PHENOL AND HYDROQUINONE
BY PRENOL IN THE PRESENCE OF
ORGANOALUMINUM CATALYSTS
*
I. Yu. Chukicheva, I. V. Fedorova,
A. A. Koroleva, and A. V. Kuchin
Prenylphenols and 2,2-dimethylbenzopyrans were synthesized via alkylation of phenol and hydroquinone
with prenol in the presence of organoaluminum catalysts, i.e., aluminum phenoxide and isopropoxide. Reaction
products were isolated and characterized. Several reaction features were determined.
Keywords: phenol, hydroquinone, prenol, organoaluminum catalysts, alkylation.
Prenylated aromatic compounds are a component part of biological systems and act as regulators of vital processes.
The 2,2-dimethylchromane ring occurs in many natural and synthetic compounds which exhibits various types of biological
activity including antioxidant, antitumor, antihypertensive, anticancer, antithrombotic, etc. [1–6]. 2,2-Dimethylbenzopyrans
showed potential as chemotherapeutic or chemopreventive candidates [7]. Compounds containing a 2,2-dimethylchromane
ring can interact with a broad spectrum of cellular targets to produce a variety of biological activities [6]. Therefore,
the development of selective synthetic methods for such compounds is of great interest.
The classical method for preparing prenylphenols and benzopyrans is acid-catalyzed alkylation of phenols by isoprene,
prenyl bromide, or prenol [8–14]. The catalysts are organic and inorganic acids [8, 9], Lewis acids [10, 12], and clays [14].
Various alkylation products are produced at the same level as the chromanes by the temperature and catalyst under these
reaction conditions.
Previously, alkylation of phenol by allylic terpene alcohols (geraniol and nerol) using the Al-containing catalysts
(PhO) Al and (i-PrO) Al was reported by us [15, 16]. The reaction of phenol with geraniol was directed mainly at C-alkylation
3
3
to give mono- and disubstituted phenols (overall yield 79%) if equimolar (reagent) amounts of (i-PrO) Al were used. Up to
3
58% chromanes were formed if (PhO) Al was used. Alkylation of phenol by geraniol in the presence of catalytic amounts of
3
(i-PrO) Al and (PhO) Al produced mainly ortho- and para-prenylphenols in overall yields up to 61%. Hydroquinone was
3
3
alkylated by geraniol using equimolar amounts of (i-PrO) Al to form up to 72% chromane ethers although mainly C-alkylation
3
products (71%) were isolated in the presence of (PhO) Al [17].
3
1
O
OR
1
3
OH
OH
OH
1
OH
R
R
R
cat.
6
6
3 - 10
+
OH
5
7
1
2
3
4
5a,b
6a,b
7a,b
R
4'
3'
5'
1
O
4'
10
3
1'
OH
R
2
O
3
9
7
3'
5b,6b,7b: R =
3,5a,6a,7a: R =
5'
1'
5
12
6
11
7
R
1
9, 10
8
9: R = H, R = OH; 10: R = OH, R = H
1
2
1
2
Scheme 1
Institute of Chemistry, Komi Scientific Center, Ural Branch, Russian Academy of Sciences, 48 Pervomaiskaya St.,
Syktyvkar, 167000, Russian Federation, fax: +7 (8212) 21 84 77, e-mail: chukicheva-iy@chemi.komisc.ru. Translated from
Khimiya Prirodnykh Soedinenii, No. 1, January–February, 2018, pp. 5–9. Original article submitted April 18, 2017.
©
0009-3130/18/5401-0001 2018 Springer Science+Business Media, LLC
1

TABLE 1. Conditions for and Products from Alkylation of Phenol by Prenol, %
5
6
7
Reaction
conditions
Conversion, %
*
**
3
4
8
9
10
à
b
à
b
à
b
(PhO)3Al, 10 mass% of starting phenol, PhOH–prenol 1:1
120ꢀC, 8 h
160ꢀC, 3 h
40
96
31
–
–
–
4
5
35
52
–
9
26
9
–
4
–
–
–
–
–
–
4
21
–
–
(PhO)3Al–prenol 1:1
120ꢀC, 2 h
160ꢀC, 1 h
96
98
–
–
44
56
–
–
–
–
–
–
–
–
17
–
–
–
16
22
14
6
–
6
–
–
9
10
______
*Prenol polymerization products; **resinous products.
TABLE 2. Conditions for and Products from Alkylation of Hydroquinone by Prenol, %
Reaction conditions
Conversion, %
*
**
12
13
14
15
16
17
(i-PrO)3Al, 10 mass% of starting phenol, hydroquinone–prenol 1:1
120°C, 10 h
160°C, 6 h
97
97
–
4
–
–
–
–
–
11
10
16
65
46
11
2
14
21
Hydroquinone–prenol–(i-PrO)3Al 1:1:1
120°C, 2 h
160°C, 1 h
______
96
98
–
–
14
16
18
30
51
41
2
–
6
–
9
13
–
–
Designations are the same as in Table 1.
1
O
1
O
1
O
3
3
6
6
OH
7
5
5
4'
3'
cat.
R
O
R
+
12 - 17
O1'
O
1'
O
OH
3'
OH
14
15
12
13
OH
11
2
OH
O
1
2
R
R
R
6
2 R
4
3
6
5
1
3
R
5
R =
4
O
OH
O
16a
16b
17
Scheme 2
Herein, the alkylation of phenol 1 and hydroquinone 11 by the natural allylic alcohol prenol (3-methyl-2-buten-1-ol, 2) was
studied (Schemes 1 and 2). Catalytic and equimolar amounts of the organoaluminum compounds [(PhO) Al and (i-PrO) Al]
3
3
were reacted at 120 and 160°C to give mixtures of O- and C-alkylation products.
Alkylation of 1 by 2 in the presence of catalytic amounts of (PhO) Al at 120°C for 8 h had a low conversion of 40%
3
(Scheme 1, Table 1). Furthermore, phenol ether 3 and alkylated phenols ortho-6a and para-7a were formed in approximately
equal amounts. Dialkylated phenol 5 and prenol polymerization products were isolated in equal amounts as side products.
The conversion increased to 96% and the yield of 6a increased to 52% if the reaction mixture was heated to 160°C. However,
the yield of polymerized starting prenol increased to 21%.
The structures of the synthesized compounds were confirmed using NMR spectroscopy. The spectral characteristics
of 3–6 agreed with those given in the literature [18–20].
Alkylation of 1 by 2 using equimolar amounts of (PhO) Al gave high conversions after 1–2 h. At 120°C, the
3
predominant product was chromane 4 (44%) and the yield of 7a was 17%. Under these same conditions, diarylalkanes 8 and
2

9 were formed in about equal amounts (16 and 14%). Increasing the reaction temperature to 160°C increased the yields of 4
and 8 and produced diarylalkane 10 (6%). The formation of diarylalkanes was a distinctive feature of the reagent method for
alkylating (PhO) Al by prenol. The starting terpenoid isomerized only if heated to 160°C in the presence of catalytic amounts
3
of (PhO) Al.
3
Complicated mixtures of O- and C-alkylation products formed during alkylation of bifunctional hydroquinone (11)
by prenol (2) in the presence of catalytic and reagent amounts of (i-PrO) Al at 120 and 160°C (Scheme 2).
3
Catalytic amounts of (i-PrO) Al at 120°C gave ortho-prenylhydroquinone (17) as the main product (65% yield).
3
The overall yield of polymerization products and resins was 22–25%. Increasing the reaction temperature to 160°C decreased
the yield of 17 and formed chromane 15. Diprenyl ether 12 was isolated as a pure side product and characterized structurally.
Bifunctional phenols are readily oxidized. This explained the formation of rather large amounts (6–10%) of dialkylated
quinones 16.
Mainly chromanes 13, 14, and 15 (overall yields of 83–87%) were formed if the reaction was conducted using
equimolar amounts of (i-PrO) Al (Table 2). Quinones 16 and ortho-prenylhydroquinone (17) appeared as minor components.
3
The yield of polymerization products under these conditions was much lower (9–13%). Products containing isomerized
terpene fragments were not detected. The structures of the synthesized compounds were confirmed using NMR spectroscopy.
The spectral characteristics of 13–15 and 17 agreed with those given in the literature [8, 11, 14, 21].
Thus, alkylation of phenol and hydroquinone by prenol in the presence of equimolar and catalytic amounts of
organoaluminum catalysts was studied. Reactions using reagent amounts of (PhO) Al or (i-PrO) Al were selective for preparing
3
3
chromanes. Catalytic amounts of the organoaluminum catalysts enhanced effective production of prenylphenols.
EXPERIMENTAL
13
PMR and C NMR spectra were recorded in CDCl at room temperature using residual solvent resonances (ꢁ 7.26,
3
H
1
13
ꢁ 77.00 ppm) as standards on a Bruker Avance II 300 spectrometer (300 MHz for H, 75 MHz for C). Resonances were
assigned using C NMR spectra recorded in JMOD mode and, in several instances, two-dimensional NMR spectroscopy
C
13
methods (COSY and HSQC). Diffuse reflectance IR spectra were recorded from KBr pellets for solids and from thin layers for
liquids on a Shimadzu IRPrestige 21 FTIR spectrometer. Reaction products were separated by column chromatography (wet
packing method) over silica gel (Alfa Aesar, 0.06–0.2 mm) using petroleum ether (bp 65–70°C). Hydroquinone (chemically
pure and 3-methyl-2-buten-1-ol (prenol, AlfaAesar) were used without further purification. Other solvents and reagents were
freshly distilled. The catalysts were (i-PrO) Al (AlfaAesar) and (PhO) Al (synthesized in situ). Melting points were determined
3
3
on a Sanyo Gallenkamp MDP350 apparatus and are uncorrected.
Alkylation of Phenol by Prenol in the Presence of (PhO) Al. Phenol (1.0 g, 11 mmol) in a two-necked flask
3
equipped with a thermometer and reflux condenser was heated to 160°C. Al turnings (0.008 g, 0.3 mmol for the catalytic
method or 0.095 g, 3.5 mmol for equimolar amounts of catalyst) were added in small portions. After the Al was completely
dissolved, the mixture was cooled to 40°C, treated with prenol (0.92 g, 10 mmol), and held at 120 or 160°C until the prenol
was fully converted. The course of the reaction was followed using TLC (petroleum ether–Et O, 3:1, vanillin detector). When
2
the reaction was finished, the mixture was cooled, diluted with Et O, treated with HCl solution (50%) to decompose the
2
catalyst, and washed with NaOH solution (5%) and H O until neutral. The organic layer was dried over anhydrous Na SO .
2
2
4
The solvent was removed. The products were separated by column chromatography using petroleum ether–Et O with increasing
2
fraction of the latter. Table 1 presents the contents of alkylation products.
–1
(3-Methylbut-2-enyloxy)benzene (3), light-yellow oil. IR spectrum (thin layer, ꢂ, cm ): 2922, 2852, 1462 and
1377 (ÑÍ , ÑÍ ), 1639 and 1597 (Ñ=Ñ), 1234, 1180, and 1109 (C–O–C) [22, 23]. Í NMR spectrum (300 MHz, CDCl ,
1
3
2
3
ꢁ, ppm, J/Hz): 1.79, 1.84 (each 3Í, s, 4ꢃ, 5ꢃ-CH ), 4.56 (2Í, d, J = 6.7, Í-1ꢃ), 5.55 (1Í, t, J = 6.7, Í-2ꢃ), 6.95–7.00 (3H, m,
3
13
ArH), 7.29–7.35 (2Í, m, ArH). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 14.12 (ÑÍ , C-4ꢃ), 25.83 (ÑÍ , C-5ꢃ), 64.67
3
3
3
(ÑÍ , C-1ꢃ), 114.68 (2ÑÍ, C-2, 6), 119.81 (ÑÍ, C-2ꢃ), 120.59 (ÑÍ, C-4), 129.41 (2ÑÍ, Ñ-3, 5), 132.05 (Ñ, Ñ-3ꢃ), 153.02
2
(Ñ, Ñ-1).
1
2,6-Bis(3-methylbut-2-enyl)phenol (5a), light-yellow oil. Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz):
1.83 (12Í, s, CH ), 3.30 (4H, d, J = 7.5, Í-1ꢃ), 5.27 (1Í, s, OH), 5.29–5.41 (2H, m, Í-2ꢃ), 6.99–7.02 (3Í, m, ArH). C NMR
3
13
3
spectrum (75 MHz, CDCl , ꢁ, ppm): 17.87 (2ÑÍ , 2 ꢄ Ñ-4ꢃ), 25.78 (2ÑÍ , 2 ꢄ Ñ-5ꢃ), 29.73 (2ÑÍ , 2 ꢄ Ñ-1ꢃ), 120.75 (ÑÍ,
3
3
3
2
C-4), 121.87 (2ÑÍ, 2 ꢄ Ñ-2ꢃ), 126.92 (2Ñ, C-2, 6), 127.50 (ÑÍ, C-5), 129.96 (ÑÍ, C-3), 134.24 (2Ñ, 2 ꢄ Ñ-3ꢃ), 154.30 (Ñ, C-1).
3

1
2,6-Bis(2-methylbut-2-en-2-yl)phenol (5b), light-yellow oil. Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm): 1.58,
3
1.76 (each 6Í, s, CH ), 4.80 (1Í, s, OH), 4.95–5.06 (4H, m, 2 ꢄ Í-3ꢃ), 5.81–5.89 (2H, m, 2 ꢄ Í-2ꢃ), 6.77–6.87 (3Í, m, ArH).
3
13
C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 14.10 (4ÑÍ , 2 ꢄ Ñ-4ꢃ, 5ꢃ), 37.76 (2Ñ, 2 ꢄ Ñ-1ꢃ), 114.06 (2ÑÍ , 2 ꢄ Ñ-3ꢃ),
3
3
2
120.87 (ÑÍ, C-4), 126.03 (ÑÍ, C-3, 5), 130.11 (2Ñ, C-2, 6), 139.28 (2ÑÍ, 2 ꢄ Ñ-2ꢃ), 146.12 (Ñ, C-1).
–1
2-(3-Methylbut-2-enyl)phenol (6a), light-yellow oil. IR spectrum (thin layer, ꢂ, cm ): 3448 (ÎÍ), 1589 (Ñ=Ñ),
1
1458, 1377 (ÑÍ , ÑÍ ), 754 (=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.83 (6Í, s, CH ), 3.41 (2H, d,
3
2
3
3
13
J = 7.5, Í-1ꢃ), 5.27 (1Í, s, OH), 5.36–5.38 (1H, m, Í-2ꢃ), 6.86–6.95 (2Í, m, Í-4, 6), 7.14–7.16 (2Í, m, Í-3, 5). C NMR
spectrum (75 MHz, CDCl , ꢁ, ppm): 17.87 (CÍ , Ñ-4ꢃ), 25.78 (CÍ , Ñ-5ꢃ), 29.73 (ÑÍ , C-1ꢃ), 115.70 (ÑÍ, C-6), 120.75 (ÑÍ,
3
3
3
2
C-4), 121.87 (ÑÍ, C-2ꢃ), 126.92 (Ñ, C-2), 127.50 (ÑÍ, C-4), 129.96 (ÑÍ, C-3), 134.24 (Ñ, C-3ꢃ), 154.30 (Ñ, C-1).
1
4-(2-Methylbut-3-en-2-yl)phenol (6b), light-yellow oil. Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm): 1.78 (6Í,
3
13
s, CH ), 4.80 (1Í, s, OH), 4.95–5.10 (2H, m, Í-3ꢃ), 5.34–5.36 (1H, m, Í-2ꢃ), 6.78–6.96 (4Í, m, ArH). C NMR spectrum
3
(75 MHz, CDCl ꢁ, ppm): 14.10 (2CÍ , Ñ-4ꢃ, 5ꢃ), 37.76 (Ñ, C-1ꢃ), 114.06 (ÑÍ , C-3ꢃ), 120.87 (2ÑÍ, C-4, 6), 126.03 (2ÑÍ,
3,
3
2
C-3, 5), 130.11 (Ñ, C-2), 139.28 (ÑÍ, C-2ꢃ), 146.12 (Ñ, C-1).
–1
4-(3-Methylbut-2-enyl)phenol (7a), light-yellow oil. IR spectrum (thin layer, ꢂ, cm ): 3369 (ÎÍ), 1512 and 1612
1
(Ñ=Ñ), 1448 and 1377 (ÑÍ , ÑÍ ), 1224 (=Ñ–O), 820 (=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.76,
2
3
3
1.78 (each 3Í, s, CH -4ꢃ, 5ꢃ), 3.31 (2H, d, J = 7.30, Í-1ꢃ), 5.02 (1Í, s, OH), 5.32–5.37 (1H, m, Í-2ꢃ), 6.79 (2Í, d, J = 7.38,
3
13
Í-2, 6), 7.08 (2Í, d, J = 7.38, Í-3, 5). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 17.77 (ÑÍ , C-4ꢃ), 25.74 (ÑÍ , C-5ꢃ),
3
3
3
29.73 (ÑÍ , C-1ꢃ), 114.96 (2ÑÍ, C-2, 6), 123.65 (ÑÍ, C-2ꢃ), 129.34 (2ÑÍ, C-3, 5), 132.18 (Ñ, C-4), 133.85 (Ñ, C-3ꢃ), 153.74
2
(Ñ, C-1).
1
4-(2-Methylbut-2-en-2-yl)phenol (7b), light-yellow oil. Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.75
3
(6Í, s, CH -4ꢃ, 5ꢃ), 4.95–5.05 (2H, m, Í-3ꢃ), 5.31 (1Í, s, OH), 5.78–5.90 (1H, m, Í-2ꢃ), 6.78 (2Í, d, J = 9.6, Í-2, 6), 7.10 (2Í,
3
13
d, J = 9.6, Í-3, 5). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 14.75 (2ÑÍ , C-4ꢃ, 5ꢃ), 31.86 (Ñ, C-1ꢃ), 114.08 (ÑÍ , C-3ꢃ),
3
3
2
120.89 (ÑÍ, C-2, 6), 129.03 (2ÑÍ, C-3, 5), 135.46 (Ñ, C-4), 139.65 (ÑÍ, C-2ꢃ), 146.24 (Ñ, C-1).
–1
2,2-Dimethylchromane (4), light-yellow oil. IR spectrum (thin layer, ꢂ, cm ): 2976 and 2929, 1375 and 1489 (ÑÍ ,
2
1
ÑÍ ), 1608 and 1581 (Ñ=Ñ), 1255–1220 (=Ñ–Î), 1155 (іΖÑ), 754 (=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm,
3
3
J/Hz): 1.39 (6Í, s, 2 CH ), 1.84–1.88 (2Í, m, H-3), 2.83 (2Í, t, J = 6.7, H-4), 6.82–6.90 (2Í, m, Í-6, 8), 7.10–7.16 (2Í, m,
3
13
Í-5, 7). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.49 (ÑÍ , Ñ-4), 26.92 (2CÍ ), 32.85 (ÑÍ , C-3), 74.10 (Ñ, C-2),
3
2
3
2
117.27 (ÑÍ, C-8), 119.62 (ÑÍ, C-6), 120.94 (Ñ, Ñ-4a), 127.27 (ÑÍ, Ñ-7), 129.46 (ÑÍ, C-5), 154.03 (Ñ, Ñ-8a).
2-[3-(2,2-Dimethylchroman-8-yl)-3-methylbutyl]phenol (8), light-yellow powder, mp 106–107ꢀÑ. IR spectrum
–1
(KBr, ꢂ, cm ): 3363 (ÎÍ), 2924, 2854, 1498 and 1365 (ÑÍ , ÑÍ ), 1247 and 1207 (=Ñ–Î), 1120 (іΖÑ), 1604 and 1587
2
3
1
(Ñ=Ñ), 819, 750 (=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.36 (6Í, s, 2 ÑÍ ), 1.48 (6Í, s, 2 ÑÍ ), 1.81
3
3
3
(2Í, t, J = 6.7, Í-7), 2.16–2.21 (2Í, m, Í-3), 2.24–2.28 (2Í, m, Í-4), 2.75 (2Í, t, J = 6.7, Í-8), 4.90 (1Í, s, ÎÍ), 6.68–6.71,
13
6.84–6.96, 7.10–7.15 and 7.28–7.29 (7Í, all m, ArH). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.50 (ÑÍ , Ñ-4), 26.89
3
2
and 28.25 (2ÑÍ ), 30.90 (ÑÍ , Ñ-8), 32.96 (ÑÍ , Ñ-3), 38.07 (Ñ, Ñ-6), 43.12 (ÑÍ , Ñ-7), 73.95 (Ñ, Ñ-2), 114.09 (Ñ, Ñ-4a),
3
2
2
2
120.41 (Ñ, Ñ-11), 116.40, 116.86, 120.58, 127.10, 127.18, 128.29 and 128.97 (7ÑÍ, Ar), 134.49 (Ñ, Ñ-5), 151.71 (Ñ, Ñ-5a),
154.15 (Ñ, Ñ-12).
2-[4-(2,2-Dimethylchroman-8-yl)-2-methylbutan-2-yl]phenol (9), light-yellow oil. IR spectrum (thin layer, ꢂ,
–1
cm ): 3525 (ÎÍ), 2926, 2854, 1448 and 1365 (ÑÍ , ÑÍ ), 1246 and 1201 (=Ñ–Î), 1120 (іΖÑ), 1587 (Ñ=Ñ), 819, 748
2
3
1
(=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.37 (6Í, s, 2 ÑÍ ), 1.51 (6Í, s, 2 ÑÍ ), 1.83 (2Í, t, J = 6.8,
3
3
3
Í-7), 2.07–2.13 (2Í, m, Í-3), 2.34–2.40 (2Í, m, Í-4), 2.81 (2Í, t, J = 6.7, Í-6), 4.85 (1Í, s, ÎÍ), 6.73–6.78, 6.91–6.99,
13
7.12–7.17 and 7.36–7.38 (7Í, all m, ArH). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.71 (ÑÍ , Ñ-4), 26.42 (ÑÍ ,
3
2
2
Ñ-6), 27.02 and 28.21 (2ÑÍ ), 32.89 (ÑÍ , Ñ-3), 38.10 (Ñ, Ñ-8), 41.98 (ÑÍ , Ñ-7), 73.90 (Ñ, Ñ-2), 120.49 (Ñ, Ñ-4a), 117.00,
3
2
2
119.07, 120.75, 126.93, 127.04, 127.59 and 128.24 (7ÑÍ, Ar), 131.42 (Ñ, Ñ-5), 134.84 (Ñ, Ñ-11), 151.63 (Ñ, C-5a), 154.31
(Ñ-12).
1
4-[4-(2,2-Dimethylchroman-8-yl)-2-methylbutan-2-yl]phenol (10), light-yellow oil. Í NMR spectrum (300 MHz,
CDCl , ꢁ, ppm, J/Hz): 1.37 (6Í, s, 2 ÑÍ ), 1.51 (6Í, s, 2 ÑÍ ), 1.83 (2Í, t, J = 6.8, Í-7), 2.07–2.13 (2Í, m, Í-3), 2.34–2.40
3
3
3
(2Í, m, Í-4), 2.81 (2Í, t, J = 6.7, Í-6), 4.90 (1Í, s, ÎÍ), 6.70–6.73, 6.82–6.85, 6.99–7.15, 7.30–7.40 (7Í, all m, ArH).
13
C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.71 (ÑÍ , Ñ-4), 26.42 (ÑÍ , Ñ-6), 27.02 and 28.21 (2ÑÍ ), 32.89 (ÑÍ ,
3
2
2
3
2
Ñ-3), 38.10 (Ñ, Ñ-8), 41.98 (ÑÍ , Ñ-7), 73.90 (Ñ, Ñ-2), 120.49 (Ñ, Ñ-4a), 114.74, 120.75, 121.56, 126.93, 127.04, 127.59 and
2
127.11 (7ÑÍ, Ar), 131.42 (Ñ, Ñ-5), 134.84 (Ñ, Ñ-11), 151.63 (Ñ, C-5a), 154.31 (Ñ, Ñ-14).
4

Alkylation of Hydroquinone by Prenol in the Presence of (i-PrO) Al (catalytic method). Hydroquinone (1.0 g,
3
9 mmol), prenol (0.78 g, 9 mmol), and (i-PrO) Al (0.10 g, 0.5 mmol) were heated in a two-necked flask equipped with a
3
thermometer and reflux condenser to 120 or 160°C until the prenol was completely converted (GC and TLC monitoring). The
reaction mixture was worked up and products were separated analogously to the method described above.
–1
3-Methyl-1-(3-methylbut-2-enyloxy)but-2-ene (12), light-yellow oil. IR spectrum (KBr, ꢂ, cm ): 1676 (Ñ=C),
1
1456 and 1380 (Ñ(ÑÍ ) ), 1108 and 1088 (іΖÑ). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.71 (6Í, s, ÑÍ ),
3 2
3
3
13
1.78 (6Í, s, ÑÍ ), 3.98 (4Í, d, J = 5.1, Í-1, 1ꢃ), 5.40 (2Í, t, J = 6.9, Í-2, 2ꢃ). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm):
3
3
25.79 (4ÑÍ , Ñ-5, 5ꢃ, 4, 4ꢃ), 66.46 (2ÑÍ , Ñ-1, 1ꢃ), 121.40 (2ÑÍ, Ñ-2, 2ꢃ), 134.75 (2Ñ, Ñ-3, 3ꢃ).
3
2
–1
2,2-Dimethylchroman-6-ol (15), brown oil. IR spectrum (thin layer, ꢂ, cm ): 3387 (ÎÍ), 2974, 2931, 1365 and
1348 (ÑÍ , ÑÍ ), 1618 and 1494 (Ñ=Ñ), 1244 and 1199 (=Ñ–Î), 1157 (іΖÑ), 925 and 812 (=Ñ–Í). Í NMR spectrum
1
2
3
(300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.35 (6Í, s, 2 CH ), 1.81 (2H, t, J = 6.76, Í-3), 2.74 (2H, t, J = 6.76, Í-4), 5.03 (1Í, br.s,
3
3
13
OH), 6.60–6.71 (3H, m, Ar). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.64 (ÑÍ , C-4), 26.73 (2CÍ ), 32.80 (ÑÍ ,
3
2
3
2
C-3), 74.01 (Ñ, C-2), 114.61 (ÑÍ, C-5), 115.57 (ÑÍ, C-7), 117.94 (ÑÍ, Ñ-8), 121.85 (Ñ, Ñ-4a), 147.79 (Ñ, Ñ-8a), 148.59 (Ñ,
Ñ-6).
1
2,6-Di-(3-methylbut-2-enyl)benzo-1,4-quinone (16a), light-brown oil. Í NMR spectrum (300 MHz, CDCl , ꢁ,
3
ppm, J/Hz): 1.66 (6Í, s, 2 CH ), 1.79 (6Í, s, 2 CH ), 3.15 (4Í, m, Í-1, 1ꢃ), 5.18 (2Í, t, J = 7.2, Í-2, 2ꢃ), 6.50 (2Í, s, Í-3, 5).
3
3
13
C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 17.76 (2ÑÍ , Ñ-4, 4ꢃ), 25.75 (2ÑÍ , C-5, 5ꢃ), 27.68 (2ÑÍ , Ñ-1, 1ꢃ), 118.18
3
3
3
2
(2ÑÍ, C-2, 2ꢃ), 132.17 (ÑÍ, Ñ-3, 5), 134.51 (2Ñ, C-3, 3ꢃ), 148.65 (2Ñ, Ñ-2, 6), 184.96 (2Ñ, Ñ-1, 4).
1
2,5-Di-(3-methylbut-2-enyl)benzo-1,4-quinone (16b), light-brown oil. Í NMR spectrum (300 MHz, CDCl , ꢁ,
3
ppm, J/Hz): 1.66 (6Í, s, 2 CH ), 1.79 (6Í, s, 2 CH ), 3.14 (4Í, m, Í-1, 1ꢃ), 5.18 (2Í, t, J = 7.2, Í-2, 2ꢃ), 6.50, 6.54 (each
3
3
13
1H, s, Í-3, 6). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 17.75 (2ÑÍ , Ñ-4, 4ꢃ), 25.72 (2ÑÍ , C-5, 5ꢃ), 27.19 (2ÑÍ ,
3
3
3
2
Ñ-1, 1ꢃ), 118.18 (2ÑÍ, C-2, 2ꢃ), 132.116 (ÑÍ, Ñ-6), 132.51 (ÑÍ, Ñ-3), 136.20 (Ñ, C-3, 3ꢃ), 148.29 (Ñ, Ñ-2, 5), 188.21
(2Ñ, Ñ-1, 4).
–1
2-(3-Methylbut-2-enyl)benzene-1,4-diol (17), yellow oil. IR spectrum (thin layer, ꢂ, cm ): 3219 (ÎÍ), 1516 (Ñ=Ñ),
1
1452 (ÑÍ , ÑÍ ), 758 (=Ñ–Í). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz):) 1.80 (6Í, s, 2CH ), 3.33 (2H, d,
3
2
3
3
13
J = 6.9, Í-1), 4.50 (1Í, s, OH), 4.79 (1Í, s, OH), 5.33 (1H, t, J = 6.9, Í-2), 6.60–6.73 (3Í, m, ArH). C NMR spectrum
(75 MHz, CDCl , ꢁ, ppm): 17.86 (ÑÍ , C-4), 25.77 (ÑÍ , C-5), 29.68 (ÑÍ , C-1), 113.73 (ÑÍ, C-3), 116.46 (ÑÍ, C-6),
3
3
3
2
116.62 (ÑÍ, C-5), 121.42 (ÑÍ, C-2), 128.50 (Ñ, C-3), 136.36 (Ñ, C-2), 148.12 and 149.32 (2Ñ, C-1, 4).
Alkylation of Hydroquinone by Prenol in the Presence of (i-PrO) Al (reagent method). Hydroquinone (1.0 g,
3
9 mmol), prenol (0.78 g, 9 mmol), and (i-PrO) Al (1.85 g, 9 mmol) in a two-necked flask equipped with a thermometer and
3
reflux condenser were heated to 120 or 160°C. The course of the reaction was followed using TLC (petroleum ether–Et O,
2
3:1, vanillin detector). The reaction mixture was worked up and products were separated analogously to the method described
above.
–1
Mixture of 13 and 14, light-yellow oil. IR spectrum (thin layer, ꢂ, cm ): 2972, 2926, 1471 and 1373 (ÑÍ , ÑÍ ),
2
3
1498 (Ñ=Ñ), 1255 and 1190 (=Ñ–Î), 1159 and 1120 (іΖÑ), 954 and 869 (=Ñ–Í).
2,2,7,7-Tetramethyl-2,3,4,7,8,9-hexahydropyrano[2,3-g]chromane (13), light-brown powder, mp 155–156°C
1
(lit. 157–158°C [8, 14]). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm, J/Hz): 1.34 (12Í, s, 4 CH ), 1.77–1.81 (4H, m,
3
3
13
Í-3, 3ꢃ), 2.58–2.62 (4H, m, Í-4, 4ꢃ), 6.63 (2H, s, ArH). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 20.05 (2ÑÍ , C-4, 4ꢃ),
3
2
26.61 (4CH ), 32.79 (2ÑÍ , C-3, 3ꢃ), 72.76 (Ñ, C-2ꢃ), 116.06 (2ÑÍ, Ñ-5, 6), 119.57 (2Ñ, Ñ-4a; 4aꢃ), 145.59 (2Ñ, C-5a, 6a).
3
2
3,3,8,8-Tetramethyl-1,2,3,8,9,10-hexahydropyrano[3,3-f]chromane (14), light-brown powder, mp 144–145°C
1
(lit. 141–146°C [8, 14]). Í NMR spectrum (300 MHz, CDCl , ꢁ, ppm): 1.34 (12Í, s, 4 ꢄ CH ), 1.77–1.81 (4H, m, Í-3, 3ꢃ),
3
3
13
2.71–2.76 (4H, m, Í-4, 4ꢃ), 6.53 (2H, s, Í-5, 6). C NMR spectrum (75 MHz, CDCl , ꢁ, ppm): 22.38 (2ÑÍ , C-4, 4ꢃ), 26.83
3
2
(4CH ), 33.01 (2ÑÍ , C-3, 3ꢃ), 73.56 (Ñ, C-2, 2ꢃ), 116.70 (2ÑÍ, Ñ-5, 6), 120.04 (2Ñ, Ñ-4a; 4aꢃ), 147.03 (Ñ, Ñ-5a, 6a).
3
2
ACKNOWLEDGMENT
The work was sponsored partially by the Russian Foundation for Basic Research (Project No. 16-53-00171 Bel_a).
Spectral studies were performed using equipment at the Khimiya CCU, Institute of Chemistry, Komi SC, UB, RAS.
5

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