Reaction of some alkenols with tetrachloromethane

Article abstract of DOI:10.1007/s007060070042

The reaction of some alkenols with tetrachloromethane in the presence of a radical initiator was investigated. Regarding the effects of structural features of the starting alkenol (number and position of methyl substituents at the double bond and at the carbinol carbon atom, constitutional relationship between the double bond and the hydroxyl group) there are two possible competing reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and with a more remote double bond) addition occurs; mono-and disubstituted secondary and tertiary Δ⁴-and Δ⁵-alkenols cyclize in high yields to give the corresponding cyclic ethers.

Full text of DOI:10.1007/s007060070042

Monatshefte fuÈr Chemie 131, 1091±1096 (2000)
Reaction of Some Alkenols with
Tetrachloromethane
Ã
and Stanimir Konstantinovic
Ï Â
Zorica M. Bugarcic , Biljana Mojsilovic, Ljiljana Marjanovic,
Â
Â
Â
University of Kragujevac, Faculty of Science, Department of Chemistry, YU-34000 Kragujevac,
Yugoslavia
Summary. The reaction of some alkenols with tetrachloromethane in the presence of a radical
initiator was investigated. Regarding the effects of structural features of the starting alkenol (number
and position of methyl substituents at the double bond and at the carbinol carbon atom, constitutional
relationship between the double bond and the hydroxyl group) there are two possible competing
reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and
with a more remote double bond) addition occurs; mono- and disubstituted secondary and tertiary
Á4- and Á5-alkenols cyclize in high yields to give the corresponding cyclic ethers.
Keywords. Addition; Alkenols; Cyclization; Tetrachloromethane; Radical initiator.
Introduction
Substituted tetrahydrofuran and tetrahydropyran rings are common in many naturally
occuring products, and thus play an important role as building blocks for the
syntheses of various biologically active organic molecules [1]. Intramolecular
cyclization of unsaturated alcohols has become a convenient route for the con-
struction of these oxacyclic compounds [2]. In continuation of our studies on electro-
phile-assisted intramolecular cyclization of alkenols [3±6] we have investigated the
reaction of ole®nic alcohols with tetrachloromethane in the presence of a radical
initiator.
Tetrachloromethane adds to a double bond in the presence of radical initiators
(acyl peroxides) as a result of a radical chain reaction [7]. Reactions can be
complicated by rearrangement and/or elimination of hydrogen chloride. Such
rearrangements involving a halogen shift have been reviewed by Friedlina [8]. A
common complication of these reactions is polymerization which often becomes
the prevailing process. On the other hand, it has recently been reported that
tetrachloromethane in the presence of dibenzoyl peroxide (DBP) is an ef®cient
reagent for the oxidation of some secondary alcohols to ketones [9].
In connection with these results, the oxidation of some alkenols with
tetrachloromethane in the presence of DBP was investigated with respect to the
Ã
Corresponding author

Ï Â
Z. M. Bugarcic et al.
1092
effect of methyl substitution at the unsaturated (trigonal) carbon atoms and at the
carbinol carbon atom as well as a function of the constitutional relationship
(distance) between the double bond and the hydroxyl group.
Results and Discussion
The reactions with CCl4 were performed by addition of the alkenols dissolved in
CCl4 to a stirred solution of dibenzoyl peroxide (DBP) as a radical initiator and
NaHCO3 in the same solvent at room temperature. The ratio of substrate to DBP
was 2:1, and tetrachloromethane served at the same time as reagent and solvent. The
reaction mixture was stirred under re¯ux for 24 h. After work-up and separation of
the reaction products the isolated products were analyzed and characterized
chromatographically and spectroscopically. The results are given in Scheme 1 and
in Table 1.
Regarding the effects of structural features in the starting alkenols in general,
two possible competing reactions may occur, one giving addition and the other one
leading to cyclization, which are illustrated in Scheme 1. The most simple alkenols
(without substituents at the double bond and at the carbinol carbon atom) do not
undergo cyclization upon treatment with tetrachloromethane. Some Á3- and Á4-
alkenols, such as 3-buten-1-ol (1a), 4-penten-1-ol (1b), and some primary and
secondary alkenols with a more remote double bond (1e±g), yield addition
products only (2a±g, Scheme 1). In contrast, the secondary and tertiary Á4- and
Á5-alkenols mono- and disubstituted at the double bond cyclize in good yield to
give the corresponding cyclic ethers 3h,i, 4h,i, and 5j,k (Scheme 1). The ring size
of the heterocyclic products was found to be in accordance with Baldwin's rules
[10]. In the case of Á4-alkenols with a terminally disubstituted double bond (1h
and 1f) the reaction was mostly dominated by the ring size and stability of the
products (favoured according to Baldwin's terminology). Two cyclic products were
Scheme 1

Reactions of Alkenols with CCl4
1093
Table 1. Reaction of alkenols with tetrachloromethane
R1
R2
R3
R4
R5
n
Products Yield/%a
1a
1b
1c
1d
1e
1f
H
H
H
H
H
0
1
2
3
3
4
5
1
1
2
2
2a
2b
80
86
85
80
60
88
84
H
H
H
H
H
H
H
H
H
H
2c
2d
H
H
CH3
H
H
H
H
H
CH3
H
H
2e
H
H
H
H
2f
2g
1g
1h
1i
H
H
H
H
H
CH3
CH3
H
CH3
CH3
H
H
CH3
CH3
CH3
CH3
H
3h‡4h
3i‡4i
5j
80b (45:55)c
H
CH3
H
86b (45:55)c
1j
1k
CH3
CH3
89
95
H
H
CH3
5k
a
b
Isolated yields; combined yields; relative distribution of the THF- and THP-type products as
c
1
evaluated by capillary GLC and H NMR analysis
likely to be formed in about equal amounts. The unsaturated tetrahydrofuran
derivatives 3h and 3i resulted from elimination of trichloromethane (which was
identi®ed in the reaction mixture). As previously reported, intramolecular
cyclization of alcohols 1h and 1i by means of t-butyl hypochlorite [5] and lead
tetraacetate [3] also affords these products. The tetrahydropyran-type products 4h
and 4i are formally derived from initial addition of a benzoyloxy radical. It has
been noticed that acyloxylation also takes place upon reaction with lead
tetraacetate and lead tetrabenzoate [3, 11]. As expected, cyclization of the Á5-
alkenols 1j and 1k afforded solely the tetrahydropyran-type products 5j and 5k in
high yields (Scheme 1 and Table 1).
All investigated secondary alkenols afforded as minor products the correspond-
ing carbonyl compounds (10±20%). Primary alkenols usually do not afford
oxidation products because of a very high activation barrier for ꢀ-hydrogen
abstraction [9].
The mechanism of the above reactions has not been studied extensively, but
current knowledge suggests that initial electrophilic attack of the reagent (CCl3Á
from CCl4) on the ꢁ-system of the double bond results in the preferential formation
of a more stable secondary or tertiary free radical as the favoured intermediate. The
decisive factors which lead to either addition or cyclization appear to be the
stability of free radicals and the activation entropy. On the one hand, in the case of
unsubstituted alkenols external nucleophilic addition of ClÁ furnished the ®nal
reaction product. On the other hand, substituted alkenols gave cyclic ether products
by internal nucleophilic addition of the hydroxylic oxygen to the initially generated
free radical.
In conclusion, the mild conditions used, inexpensive reagents, and no necessity
to use a complicated apparatus make this reaction useful for the synthesis of many
organic compounds. The method described here is thus a versatile way of
introducing one more carbon atom into alkenols. The trichloromethyl group can
then be converted to a carboxyl group [12]. Moreover, the polychloroalkanols
prepared by treatment with tetrachloromethane are suitable for the transformation

Ï Â
Z. M. Bugarcic et al.
1094
into a variety of reaction products by dehalogenation, dehydrohalogenation, and
cyclization reactions [13]. It thus appears that this procedure is of value for the
preparation of cyclic ethers and their functionalized derivatives.
Experimental
GLC analyses were obtained with a Deni 2000 instrument with capillary apolar columns. 1H and 13
C
NMR spectra were run in CDCl3 on a Varian Gemini 200 MHz NMR spectrometer. IR spectra were
obtained with Perkin-Elmer Model 137B and Nicolet 7000FT spectrophotometers. Thin layer
chromatography (TLC) was carried out on 0.25 mm (Merck) precoated silica gel plates (60F-254)
using UV light for visualization. For column chromatography silica gel 60 (Merck, particle size 0.063±
0.200 mm) was used. All ole®nic alcohols used as substrates are known compounds which are either
commercially available or were prepared according to known procedures [3, 14]. Tetrachloromethane
was dried by distillation from P2O5. Dibenzoyl peroxide (Aldrich) was puri®ed prior to use by
precipitation from a solution in CHCl3 by addition of twice its volume of methanol.
General procedure
All reactions were carried out on a 10 mmol scale. To a magnetically stirred solution of 1.21 g DBP
(5 mmol) and 0.84 g NaHCO3 (10 mmol) in 25 cm3 dry CCl4, 10 mmol alkenol dissolved in 5 cm3
CCl4 were added. Stirring was continued under re¯ux for 24 h. After completion of the reaction, the
mixture was allowed to reach room temperature. Insoluble parts were ®ltered off, and the mixture
was washed a few times with H2O and dried over Na2SO4. After drying, the solvent was distilled off,
and the residue was analyzed by gas chromatography and TLC. Reaction products were separated by
column chromatography (silica gel/CH2Cl2:petroleum ether (b.p. 40±60ꢀC) ˆ 7:3) or by preparative
gas chromatography (20% Carbowax column at 100ꢀC) and identi®ed and characterized by their
spectroscopic data.
3,5,5,5-Tetrachloropentan-1-ol (2a; C5H8OCl4)
Yield: 80%; IR (®lm): ꢂ ˆ 700, 790, 1070, 3400 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:52±1.94
(m, CH2CH2OH), 2.53 (br s, OH), 3.12 (ABX system, JAB ˆ 15:3 Hz, JAX ˆ 6:7 Hz, CHCCl3), 3.26
(ABX system, JAB ˆ 15:3 Hz, JBX ˆ 6:9 Hz, CHCCl3), 3.65 (t, J ˆ 6:0 Hz, CH2OH), 4.09 (m,
CHCl) ppm.
4,6,6,6-Tetrachlorohexan-1-ol (2b; C6H10OCl4)
Yield: 86%; IR (®lm): ꢂ ˆ 704, 790, 1060, 3400 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:62±2.17
(m, CH2CH2CH2OH), 2.61 (br s, OH), 3.13 (ABX system, JAB ˆ 15:6 Hz, JAX ˆ 6:9 Hz, CHCCl3),
3.27 (ABX system, JAB ˆ 15:6 Hz, JBX ˆ 7:0 Hz, CHCCl3), 3.67 (t, J ˆ 6:0 Hz, CH2OH), 4.11 (m,
CHCl) ppm; 13C NMR (CDCl3, DEPT, 50 MHz): ꢃ ˆ 28:83 (CH2CHCl), 35.29 (CH2CH2OH), 57.32
(CHCl), 61.17 (CH2CCl3), 62.01 (CH2OH), 95.93 (CCl3) ppm.
5,7,7,7-Tetrachloroheptan-1-ol (2c; C7H12OCl4)
Yield: 85%; IR (®lm): ꢂ ˆ 706, 790, 1064, 3420 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:53±2.05
(m, CH2CH2CH2), 2.05 (s, OH), 3.12 (ABX system, JAB ˆ 15:7 Hz, JAX ˆ 7:9 Hz, CHCCl3), 3.26
(ABX system, JAB ˆ 15:7 Hz, JBX ˆ 10:6 Hz, CHCCl3), 3.67 (t, J ˆ 6:0 Hz, CH2OH), 4.27 (m,
CHCl) ppm; 13C NMR (CDCl3, DEPT, 50 MHz): ꢃ ˆ 22:13 (CH2CH2), 31.44 (CH2CHCl), 38.47
(CH2CH2OH), 57.22 (CHCl), 61.56 (CH2CCl3), 61.87 (CH2OH), 95.82 (CCl3) ppm.

Reactions of Alkenols with CCl4
1095
6-Methyl-6,8,8,8-tetrachlorooctan-1-ol (2d; C9H16OCl4)
1
Yield: 80%; IR (®lm): ꢂ ˆ 710, 800, 1068, 3432 cm 1; H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:84 (s,
CH3), 1.33±1.85 (m, CH2CH2CH2), 1.95 (t, J ˆ 6:8 Hz, CH2CCl), 2.15 (s, OH), 3.22 (s, CH2CCl3),
3.65 (t, J ˆ 6:2 Hz, CH2OH) ppm.
7,9,9,9-Tetrachlorononan-2-ol (2e; C9H16OCl4)
Yield: 60%; IR (®lm): ꢂ ˆ 709, 810, 1062, 1411, 3416 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:22
(d, J ˆ 6:0 Hz, CH3), 1.45±2.18 (m, CH2CH2CH2), 2.16 (s, OH), 3.12 (ABX system, JAB ˆ 16:1 Hz,
JAX ˆ 6:9 Hz, CHCCl3), 3.26 (ABX system, JAB ˆ 16:1 Hz, JBX ˆ 10:6 Hz, CHCCl3), 3.68 (t,
J ˆ 6:0 Hz, CHOH), 4.25 (m, CHCl) ppm.
7,9,9,9-Tetrachlorononan-1-ol (2f; C9H16OCl4)
Yield: 88%; IR (®lm): ꢂ ˆ 705, 791, 1070, 3476 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:25±2.05
(m, CH2CH2CH2CH2), 2.31 (br s, OH), 3.12 (ABX system, JAB ˆ 15:8 Hz, JAX ˆ 7:8 Hz, CHCCl3),
3.26 (ABX system, JAB ˆ 15:8 Hz, JBX ˆ 10:5 Hz, CHCCl3), 3.69 (t, J ˆ 6:0 Hz, CH2OH), 4.25 (m,
CHCl) ppm.
8,10,10,10-Tetrachlorodecan-1-ol (2g; C10H18OCl4)
Yield: 84%; IR (®lm): ꢂ ˆ 704, 790, 1069, 3456 cm 1; 1H NMR (CDCl3, 200 MHz): ꢃ ˆ 1:25±2.05
(m, CH2CH2CH2CH2CH2), 2.23 (br s, OH), 3.12 (ABX system, JAB ˆ 15:8 Hz, JAX ˆ 7:8 Hz,
CHCCl3), 3.26 (ABX system, JAB ˆ 15:8 Hz, JBX ˆ 10:5 Hz, CHCCl3), 3.68 (t, J ˆ 6:0 Hz,
CH2OH), 4.25 (m, CHCl) ppm.
2-(1-Methylvinyl)-5-methyl-tetrahydrofuran (3h; C8H14O)
Yield: 36%; for spectroscopic data, see Ref. [3].
2-(1-Methylvinyl)-5,5-dimethyl-tetrahydrofuran (3f; C9H16O)
Yield: 39%; for spectroscopic data, see Ref. [3].
2,2,6-Trimethyl-3-benzoyloxy-tetrahydropyran (4h; C15H20O3)
1
Yield: 44%; IR (®lm): ꢂ ˆ 715, 780, 1178, 1260, 1715 cm 1; H NMR (CDCl3, COSY, 200 MHz):
ꢃ ˆ 1:22 (d, J ˆ 6 Hz, CH3CHO), 1.45±1.55 (m, CH2CHCH3), 1.61 and 1.63 (2Âs, (CH3)2CO),
1.82±1.98 (m, CHaxCHOCOPh), 1.98±2.21 (m, CHeqCHOCOPh), 4.05 (m, CHO), 5.28 (dd,
J ˆ 2 Hz and 10.1 Hz, CHOCOPh), 7.40±7.62 (m, o- and p-CH), 8.06±8.12 (m, m-CH) ppm; 13C
NMR (CDCl3, DEPT, HETCOR, 50 MHz): ꢃ ˆ 24:96 (CH2OCOPh), 28.82 and 29.35 (CH3)2CO),
31.12 (CH3CO), 39.97 (CH2CHCH3), 70.45 (CHO), 70.64 (CO), 79.86 (CHOCOPh), 128.43 (p-CH),
129.64 ( ˆ CCOO), 129.76 (o-CH), 133.73 (m-CH), 166.15 (C=O) ppm.
2,2,6,6-Tetramethyl-3-benzoyloxy-tetrahydropyran (4f; C16H22O3)
1
Yield: 47%; IR (®lm): ꢂ ˆ 715, 784, 1180, 1262, 1715 cm 1; H NMR (CDCl3, COSY, 200 MHz):
ꢃ ˆ 1:20 and 1.22 (2Âs, (CH3)2CCH2), 1.43±1.56 (m, CH2C(CH3)2), 1.62 and 1.64 (2Âs,
(CH3)2CCH), 1.82±1.98 (m, CHaxCHOCOPh), 1.98±2.21 (m, CHeqCHOCOPh), 5.28 (dd, J ˆ 2 Hz

Ï Â
Z. M. Bugarcic et al.: Reactions of Alkenols with CCl4
1096
and 10.1 Hz, CHOCOPh), 7.40±7.62 (m, o- and p-CH), 8.06±8.12 (m, m-CH) ppm; 13C NMR
(CDCl3, DEPT, HETCOR, 50 MHz): ꢃ ˆ 24:90 (CH2OCOPh), 28.76 and 29.23 (CH3)2CCH), 28.91
and 29.59 (CH3)2CCH2), 39.70 (CH2C(CH3)2), 70.52 and 70.59 (COC), 79.89 (CHOCOPh), 128.41
(p-CH), 129.66 ( ˆ CCOO), 129.75 (o-CH), 133.75 (m-CH), 166.13 (C=O) ppm.
2,6-Dimethyl-2-(1,1,1-trichloroethyl)-tetrahydropyran (5i; C9H15OCl3)
1
Yield: 89%; IR (®lm): ꢂ ˆ 710, 736, 775, 913, 1149 cm 1; H NMR (CDCl3, COSY, 200 MHz):
ꢃ ˆ 1:21 (d, J ˆ 6:0 Hz, CH3CHO), 1.40±1.54 (m, CH2CH2), 1.55±1.72 (m, CH2CHO), 1.86 (s,
CH3CO), 1.88±2.05 (m, CH2CO), 3.38 (s, CH2CCl3), 3.83 (d, J ˆ 6:0 Hz, CHO) ppm.
2,6,6-Trimethyl-2-(1,1,1-trichloroethyl)-tetrahydropyran (5j; C10H17OCl3)
1
Yield: 95%; IR (®lm): ꢂ ˆ 710, 736, 775, 913, 1149 cm 1; H NMR (CDCl3, COSY, 200 MHz):
ꢃ ˆ 1:25 (s, (CH3)2CO), 1.42±1.52 (m, CH2CH2), 1.53±1.72 (m, CH2C(CH3)2), 1.86 (s, CH3CO),
1.88±2.04 (m, CH2CCH3), 3.39 (s, CH2CCl3) ppm; 13C NMR (CDCl3, DEPT, HETCOR, 50 MHz):
ꢃ ˆ 19:25 (CH2CH2), 29.05 and 29.10 (CH3)2CO), 29.93 (CH3CO), 43.22 (CH2C(CH3)2), 44.88
(CH2CCH3), 63.94 (CH2CCl3), 70.51 C(CH3)2), 71.43 (CCH3), 95.63 (CCl3) ppm.
Acknowledgements
The authors are grateful to the Ministry of Science and Technology of Serbia for ®nancial support.
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Received March 17, 2000. Accepted (revised) May 31, 2000