A new method for alkylation of aromatic aldehydes using alkylboron chloride derivatives in the presence of oxygen

Article abstract of DOI:10.1016/S0040-4020(02)00237-5

Reactions of aromatic aldehydes with alkylboron chloride derivatives in the presence of oxygen have been investigated. Dialkylboron chlorides react with aryl aldehydes to produce arylalkylmethanols in good to excellent yields. Under the same reaction conditions, alkylboron dichlorides lead to the formation of arylalkyl chlorides.

Full text of DOI:10.1016/S0040-4020(02)00237-5

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 3243±3248
A new method for alkylation of aromatic aldehydes using
alkylboron chloride derivatives in the presence of oxygen
George W. Kabalka,p Zhongzhi Wu and Yuhong Ju
Departments of Chemistry and Radiology, University of Tennessee, Knoxville, TN 37996-1600 USA
This paper is dedicated to Professor Herbert C. Brown, a pioneer in organoboron chemistry, on the occasion of his 90th birthday
Received 27 November 2001; revised 26 February 2002; accepted 27 February 2002
AbstractÐReactions of aromatic aldehydes with alkylboron chloride derivatives in the presence of oxygen have been investigated.
Dialkylboron chlorides react with aryl aldehydes to produce arylalkylmethanols in good to excellent yields. Under the same reaction
conditions, alkylboron dichlorides lead to the formation of arylalkyl chlorides. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
presence of base (Scheme 1).23 It was found that reagents
containing secondary alkyl groups produce good yields of
alkylation products whereas those containing primary alkyl
groups produce low yields of desired products. Reduction
predominates when hindered alkylboranes are utilized.
Monoalkylboron chlorides failed to react with aldehydes
under the same reaction conditions.
The alkylation of carbonyl compounds by an organometallic
reagent is an important method for assembling a variety of
useful carbon skeletons. Generally, only reactive alkyl-
metals such as organomagnesium,1 organolithium,2 organo-
zinc3 and certain organotransition metal reagents4±9 can be
utilized to achieve this transformation. Allylborane, vinyl-
borane and alkynylborane reagents have been used to
successfully alkylate carbonyl compounds but saturated
organoboranes are typically unreactive.10±15 The earliest
attempt to achieving a Grignard-like reaction using tri-
alkylboranes resulted in the reduction of the aldehyde via
a b-hydrogen elimination.16 Although a general 1,2-addition
of a trialkylborane to a carbonyl compounds has not been
achieved, certain modi®cations in either the carbonyl
compound or the trialkylborane have led to a few successful
alkylation reactions.17,18 Nevertheless, a Grignard-like reac-
tion involving organoborane reagents would possess a
number of advantages including mild reaction conditions,
potential stereochemical control, and the fact that a large
number of functional substituents are unaffected by most
organoborane transformations.19
Organoboranes are known to undergo autoxidation in the
presence of oxygen and the reaction has been used to
prepare alcohols and alkyl hydroperoxides as well as to
initiate free radical reactions.24,25 Trialkylboranes readily
react with a,b-unsaturated carbonyl compounds through a
free radical 1,4-addition reaction in the presence of air26 but
they do not normally undergo 1,2-addition to saturated
carbonyl compounds. Only formaldehyde was reported to
react with trialkylboranes in the presence of air to produce
alkylation products.27 That reaction is believed to proceed
via a free radical mechanism, since no alkylation occurs in
the absence of oxygen.
We have examined the reaction of aryl aldehydes with a
variety of alkylboron chlorides in the presence of oxygen
and found that reactions involving dialkylboron chlorides
occur more readily than the corresponding alkylation
carried out in the absence of oxygen but in the presence
of base. Alkylboron dichlorides also produce the alkylation
products, arylalkyl chlorides, in the presence of oxygen. We
Alkylboron halide derivatives have been used extensively
for the reduction of carbonyl compounds as well as for
generating enolate reagents for aldol reactions.20,21 This
methodology has become one of the most important routes
for diastereoselective, and enantioselective carbon±carbon
bond formation.22 We recently reported the successful alkyl-
ation of aryl aldehydes using dialkylboron chlorides in the
Keywords: boron and compounds; aldehydes; alcohols; chlorides; alkyl-
ation.
p
Corresponding author. Tel.: 11-865-974-3260; fax: 11-865-974-2997;
e-mail: kabalka@utk.edu
Scheme 1.
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00237-5

3244
G. W. Kabalka et al. / Tetrahedron 58 (2002) 3243±3248
Table 1. Synthesis of arylalkylmethanols via reactions of aryldehydes with
R2BCl in the presence of oxygen
Entry
X
R
Product
Yield (%)a,b
1
2
3
4
5
6
7
8
H (1a)
4-F (1b)
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclopentyl
Cyclopentyl
Cyclopentyl
Cyclopentyl
Norbornyl
Norbornyl
Norbornyl
sec-butyl
sec-Butyl
sec-Butyl
sec-Butyl
sec-Butyl
sec-Butyl
n-Hexyl
n-Hexyl
n-Hexyl
n-Hexyl
n-Hexyl
(2a)
(2b)
(2c)
(2d)
(2e)
(2f)
(2g)
(2h)
(2i)
(2j)
(2k)
(2l)
(2m)
(2n)
(2o)
(2p)
(2q)
(2r)
90
95
98
63
95
96
88
98
94
84
92c
92
99
92
91
76
73
75
65
74
67
70
71
55
84d
75d
64d
72d
81d
4-Cl (1c)
2-Cl (1d)
4-Br (1e)
4-Me (1f)
2-Me (1g)
4-OMe (1h)
Naphthyl (1i)
1,4-(CHO)2 (1j)
4-CN (1k)
H (1l)
4-F (1m)
4-Br (1n)
4-Me (1o)
H (1p)
4-Br (1q)
4-Me (1r)
H (1s)
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Scheme 2.
nances were observed. Furthermore, upon addition of water,
4-bromobenzaldehyde was regenerated. This suggests that
4-bromobenzaldehyde reversibly coordinates to dicyclo-
hexylboron chloride. In a separate experiment, after oxygen
was introduced to a benzene solution of the yellow solid, a
(2s)
(2t)
1
new doublet appeared at 5.11 ppm in the H NMR and a
4-F (1t)
corresponding resonance appeared at 83.4 ppm in the
13C NMR. Hydrolysis of the reaction mixture led to the
formation of the desired alkylation product, (4-bromo-
phenyl)cyclohexylmethanol.
4-Cl (1u)
4-Br (1v)
4-Me (1w)
2-Me (1x)
H (1y)
4-Cl (1z)
4-Br (1aa)
4-Me (1ab)
2-Me (1ac)
(2u)
(2v)
(2w)
(2x)
(2y)
(2z)
(2aa)
(2ab)
(2ac)
The alkylation reaction is rapid but no alkylation occurs in
the presence of radical scavenger such as galvinoxyl. In
addition, when both primary and secondary alkyl groups
are present, as is generally the case when alkyl boron halides
are formed via hydroboration, the secondary group reacts
preferentially. These observations support the postulation
that the reaction is occurring via a radical pathway, such
as the one outlined in Scheme 2. A similar pathway was
reported for the reaction of trimethylboron with formalde-
hyde.27 It is also possible that the reaction involves
complexation of the alkylboron halide with carbonyl
group prior to radical attack.26g
a
Isolated yields based on starting aldehydes.
Physical and spectroscopic data are consistent with literature values.23
Two equivalents of borane were used.
Signi®cant quantities of the product containing the secondary alkyl group
are formed.
b
c
d
wish to report the results of our study of the alkylation
reactions of aryl aldehydes using alkylboron chlorides.
2. Results and discussion
2.2. The reaction of alkylboron dichlorides with aryl
aldehydes in the presence of oxygen
2.1. The reaction of dialkylboron chlorides with aryl
aldehydes in the presence of oxygen
Since only one alkyl group in dialkylboron chloride is trans-
ferred to the carbonyl carbon, the reaction would be more
ef®cient if monoalkylboron dichlorides could be utilized.
Thus, we examined the reaction of alkylboron dichlorides
with aryl aldehydes in the presence of oxygen. Interestingly,
instead of alkylarylmethanols, the reaction produces the
chloroalkylation products exclusively at room temperature.
We also noted that a small quantity of benzyl chloride
formed along with the desired alkylation products, an obser-
vation we made earlier.23,28 a,a-Dichlorotoluenes are also
formed in small quantities if reactions are carried out at the
higher temperature.29
We ®rst examined the reaction of dicyclohexylboron
chloride with benzaldehyde in hexane at room temperature
in the presence of oxygen. Surprisingly, the reaction occurs
rapidly at room temperature and produces the desired alkyl-
ation product, cyclohexylphenylmethanol, in excellent
yield. The reaction appears to be general for all aryl
aldehydes studied (Table 1). The reaction proceeds most
ef®ciently at 08C but partial reduction occurs when the reac-
tion is carried out at room temperature. In contrast to alkyl-
ation reactions carried out in the absence of oxygen,23
organoboranes containing primary and hindered alkyl
groups produce good yields of alkylation products.
In contrast to the reaction of di(n-hexyl)boron chloride
with aromatic aldehydes, isomeric products arising from
migration of a secondary alkyl group are not observed in
the reaction of n-butylboron dichloride with aryl aldehydes.
This suggests that the reaction of monoalkylboron
dichlorides may proceed via a different pathway, NMR
spectroscopy was used to monitor a representative reaction.
Benzaldehyde was mixed with one equivalent of n-butyl-
boron dichloride in benzene-d6 and the 1H and 13C
In an effort to probe the mechanism of the reaction, dicyclo-
hexylboron chloride (1 M in hexane) was added to 4-bromo-
benzaldehyde in hexane at 2308C. The solvent was
removed in vacuo to yield a yellow solid which was then
re-dissolved in benzene-d6 for NMR analysis. Interestingly,
1
the characteristic H and 13C resonances of the aldehyde
group were absent in the NMR spectra, and no new reso-

G. W. Kabalka et al. / Tetrahedron 58 (2002) 3243±3248
3245
Scheme 3.
resonances of carbonyl group were no longer observable. In
addition, no new resonances related to carbonyl group were
observed. [Only reductive chlorination occurred, leading to
the formation of benzyl chloride if reaction times were
prolonged.] In a separate experiment, oxygen was intro-
duced to the reaction mixture and the NMR spectra revealed
that the chloroalkylation product, 1-phenylpentyl chloride,
gradually formed. In addition, the addition of a radical
scavenger, galvinoxyl did not inhibit the alkylation reaction.
It is likely that this reaction proceeds via oxidation of the
organoborane to form a peroxide intermediate which then
undergoes alkyl transfer through an intramolecular six-
membered ring transition state 3 to give the borinate ester
4. The product would then form after migration of the
chlorine (Scheme 3). In a separate experiment, the reaction
was carried out at 2208C, and no alkylation occurred, but
n-butyl peroxide was isolated upon hydrolysis of the reac-
tion mixture. This experiment supports the presence of
peroxide intermediate in the reaction. In order to con®rm
the presence of intermediate 4, 1-phenylpentyloxyboron
dichloride was prepared by the reaction of lithium 1-phenyl-
pentyloxide with BCl3 which gradually led to the formation
of benzyl chloride 5 at room temperature.
A series of aryl aldehydes were subjected to the reaction
sequence. Essentially all aldehydes were successfully
converted to the corresponding chlorides (Table 2).
3. Conclusion
A new alkylation reaction has been developed which
provides a potentially useful alternative to traditional
Grignard and organolithium reactions. The reaction occurs
under mild reaction conditions and tolerates a variety of
functional groups. Dialkylboron chlorides react with aryl
aldehydes to produce the corresponding alkylarylmethanols
in excellent yields whereas alkylboron dichlorides afford the
corresponding chlorides in good yields.
4. Experimental
4.1. General
All glassware was dried in an oven at 1208C and ¯ushed
with dry argon prior to use. Hexane was distilled from CaH2.
n-Butylboron dichloride (1 M in hexane) and dicyclohexyl-
boron chloride were purchased from Aldrich Chemical
Company. Cyclohexylboron dichloride and sec-butylboron
dichloride were prepared by hydroboration of the corre-
sponding alkenes with HBCl2(SMe2) followed by addition
of BCl3.30 Dicyclopentylboron chloride, di(exo-norbornyl)-
boron chloride, di(n-hexyl)boron chloride and di(sec-butyl)-
boron chloride were prepared according to literature pro-
cedures.31 All aldehydes were dried and distilled prior to
use. Products were puri®ed by ¯ash chromatography using
Table 2. Synthesis of arylalkyl chlorides via reaction of aryl aldehydes with
RBCl2
Entry
X
R
Time (h) Product Yield (%)a
1
2
3
4
5
6
7
8
H (1a)
4-F (1b)
n-Butyl
n-Butyl
n-Butyl
n-Butyl
n-Butyl
n-Butyl
n-Butyl
n-Butyl
2
1
1
3
2
1
2
2
2
2
1
3
1
2
1
1
2
1
1
2
(5a)
(5b)
(5c)
(5d)
(5e)
(5f)
(5g)
(5h)
(5i)
62
85
75
50
51
63
45
55
73
81
79
20
86
16
92
67
65
67
74
25
4-Cl (1c)
2-Cl (1d)
3-Cl (1e)
4-Br (1f)
3-Br (1g)
4-Me (1h)
9
1,4-(CHO)2 (1i) n-Butyl
H (1j)
Ê
silica gel (60 A 230±400 mesh) with hexane as eluent for
10
11
12
13
14
15
16
17
18
19
20
Cyclohexyl
(5j)
(5k)
(5l)
4-Cl (1k)
2-Cl (1l)
4-Br (1m)
3-Br (1n)
4-F (1o)
1,4-(CHO)2 (1p) Cyclohexyl
H (1q)
4-Cl (1r)
4-F (1s)
2-Me (1t)
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
arylalkyl chlorides and methylene chloride for arylalkyl
methanols. Melting points are uncorrected. Elemental
analyses were performed by Atlantic Microlabs, Norcross,
GA. 1H NMR spectra were recorded in CDCl3 at 250 MHz.
13C NMR spectra were recorded at 62.9 MHz in CDCl3.
(5m)
(5n)
(5o)
(5p)
(5q)
(5r)
(5s)
(5t)
1
sec-Butyl
sec-Butyl
sec-Butyl
sec-Butyl
Chemical shifts are listed relative to SiMe4 for H NMR
and to CDCl3 for 13C NMR. In cases where more than one
diastereoisomer formed, the NMR shifts of all isomers are
reported. High-resolution mass spectra were obtained using
ZAB-EQ instrument.
a
Isolated yields based on starting aldehydes.

3246
G. W. Kabalka et al. / Tetrahedron 58 (2002) 3243±3248
4.2. General procedure for synthesis of
arylalkylmethanols
4.3.4. 1-(1-Chloropentyl)-2-chlorobenzene (5d). Colorless
liquid. 1H NMR: d 7.61±7.16 (m, 4H), 5.41 (t, 1H,
Jˆ6.9 Hz), 2.09±1.99 (m, 2H), 1.54±1.30 (m, 4H), 0.90
(t, 3H, Jˆ6.8 Hz). 13C NMR: d 139.3, 132.5, 129.4,
129.0, 128.4, 127.3, 59.1, 38.9, 28.9, 22.1, 13.9. HRMS:
Calcd for C11H14Cl2 [M]1, 216.0473. Found: m/z,
216.0466. Anal. Calcd for C11H14Cl2: C, 60.85; H, 6.50.
Found: C, 60.86; H, 6.53.
4-Chlorobenzaldehyde (3.0 mmol, 0.42 g) was dissolved in
hexane (10 ml) contained in a dry, argon-¯ushed, septum
sealed, 50 ml round-bottomed ¯ask and the mixture cooled
to 08C in an ice bath. Dicyclohexylboron chloride
(3.0 mmol, 3.0 ml of a 1.0 M hexane solution) was added
via a syringe to yield a yellow solution. Oxygen gas was
introduced over the reaction solution by means of an oxygen
®lled balloon attached to a 18 gauge needle. The reaction
solution gradually turned colorless. After being stirred at
room temperature for 1 h, the reaction solution was hydro-
lized. The organic layer was separated, dried over
anhydrous MgSO4, the solvent removed and the product
isolated by column chromatography to yield 0.66 g (98%
yield) of the desired product, (4-chlorophenyl)cyclohexyl-
methanol.
4.3.5. 1-(1-Chloropentyl)-4-chlorobenzene (5e). Colorless
liquid. 1H NMR: d 7.37 (s, 1H), 7.27±7.26 (m, 3H), 4.78 (t,
1H, Jˆ6.8 Hz), 2.12±1.98 (m, 2H), 1.48±1.26 (m, 4H), 0.89
(t, 3H, Jˆ6.9 Hz). 13C NMR: d 144.0, 134.4, 129.9, 128.3,
127.2, 125.2, 62.8, 39.7, 29.1, 22.1, 13.9. HRMS: Calcd for
C11H14Cl2 [M]1, 216.0473. Found: m/z, 216.0462. Anal.
Calcd for C11H14Cl2: C, 60.85; H, 6.50. Found: C, 60.72;
H, 6.45.
4.3.6. 1-(1-Chloropentyl)-4-bromobenzene (5f). Colorless
1
liquid. H NMR: d 7.47 (d, 2H, Jˆ8.4 Hz), 7.24 (d, 2H,
4.3. General procedure for synthesis of arylalkyl
chlorides
Jˆ8.4 Hz), 4.78 (t, 1H, Jˆ7.5 Hz), 2.10±1.96 (m, 2H),
1.52±1.21 (m, 4H), 0.88 (t, 3H, Jˆ6.7 Hz). 13C NMR: d
141.0, 131.7, 128.6, 122.0, 62.9, 39.6, 29.1, 22.1, 13.8.
HRMS: Calcd for C11H14BrCl [M]1, 261.9945. Found:
m/z, 261.9940.
Benzaldehyde (4.2 mmol, 0.44 g) was dissolved in hexane
(10 ml) contained in a dry, argon-¯ushed, septum sealed,
50 ml round-bottomed ¯ask. n-Butylboron dichloride
(4.2 mmol, 4.2 ml of a 1.0 M hexane solution) was added
via a syringe and the solution allowed to stir at room
temperature. Oxygen gas was introduced to the reaction
solution via a syringe needle attached to a oxygen ®lled
balloon. The reaction solution gradually turned cloudy.
After 1 h, the reaction mixture was ®ltered. The ®ltrate
was then hydrolyzed with water. The organic layer was
separated, dried over anhydrous MgSO4, and the product
isolated by column chromatography to afford 0.49 g
(62%)of the desired product, 1-(1-chloropentyl)benzene.
4.3.7. 1-(1-Chloropentyl)-3-bromobenzene (5g). Color-
less liquid. H NMR: d 7.53 (s, 1H), 7.44±7.17 (m, 3H),
1
4.77 (t, 1H, Jˆ7.1 Hz), 2.16±1.94 (m, 2H), 1.54±1.24 (m,
4H), 0.89 (t, 3H, Jˆ6.6 Hz). 13C NMR: d 144.2, 131.2,
130.1, 130.0, 125.6, 122.5, 62.7, 39.6, 29.1, 22.1, 13.8.
HRMS: Calcd for C11H14BrCl [M]1, 261.9945. Found:
m/z, 261.9952.
4.3.8. 1-(1-Chloropentyl)-4-methylbenzene (5h). Color-
1
less liquid. H NMR: d 7.26 (d, 2H, Jˆ8.1 Hz), 7.14 (d,
2H, Jˆ8.0 Hz), 4.82 (t, 1H, Jˆ7.1 Hz), 2.33 (s, 3H),
2.14±1.99 (m, 2H), 1.45±1.28 (m, 4H), 0.88 (t, 3H, Jˆ
6.8 Hz). 13C NMR: d 139.1, 138.0, 129.2, 126.8, 63.9,
39.7, 29.3, 22.1, 21.1, 13.9. HRMS: Calcd for C12H17Cl
[M]1, 190.102. Found: m/z, 190.102.
Compounds 1-(1-chloropentyl)-4-methylbenzene (5h) and
1-(1-chloro-2-methylbutyl)-4-methylbenzene (5t) decom-
pose on silica-gel column. Therefore, they were puri®ed
by vacuum distillation.
4.3.1. (1-Chloropentyl)benzene (5a). Colorless liquid.32 1H
NMR: d 7.38±7.21 (m, 5H), 4.83 (t, 1H, Jˆ7.4 Hz), 2.16±
1.97 (m, 2H), 1.51±1.24 (m, 4H), 0.88 (t, 3H, Jˆ6.6 Hz).
13C NMR: d 142.0, 128.6, 128.1, 126.9, 63.8, 39.7, 29.2,
22.1, 13.9.
4.3.9. 1,4-Di-(1-chloropentyl)benzene (5i). Colorless
1
liquid. H NMR: d 7.35 (s, 4H), 4.84 (t, 2H, Jˆ6.7 Hz),
2.33 (s, 3H), 2.14±1.99 (m, 4H), 1.50±1.26 (m, 8H), 0.89
(t, 6H, Jˆ6.7 Hz). 13C NMR: d 142.0, 127.2, 63.4, 39.9,
29.2, 22.1, 13.9. HRMS: Calcd for C16H24Cl2 [M]1,
286.1255. Found: m/z, 286.1257.
4.3.2. 1-(1-Chloropentyl)-4-¯uorobenzene (5b). Colorless
liquid. 1H NMR: d 7.36±7.30 (m, 2H), 7.04±6.97 (m, 2H),
4.81 (t, 1H, Jˆ7.45 Hz), 2.14±1.97 (m, 2H), 1.46±1.22 (m,
4H), 0.88 (t, 3H, Jˆ6.6 Hz). 13C NMR: d 164.3, 160.4,
137.9, 137.9, 128.7, 128.6, 115.6, 115.2, 62.9, 39.8, 29.1,
22.1, 13.8. Anal. Calcd for C11H14ClF: C, 65.84; H, 7.03.
Found: C, 65.90; H, 6.99.
4.3.10. 1-(Chloro-cyclohexyl-methyl)benzene (5j). Color-
less liquid.33 1H NMR: d 7.33±7.22 (m, 5H), 4.60 (d, 1H,
Jˆ8.4 Hz), 2.21±0.86 (m, 11H). 13C NMR: d 140.9, 128.3,
127.9, 127.5, 69.8, 45.7, 30.4, 30.3, 26.1, 25.9, 25.9.
4.3.11. 1-Chloro-4-(chloro-cyclohexyl-methyl)benzene
(5k). Colorless liquid.34 1H NMR: d 7.30 (d, 2H, Jˆ
8.7 Hz), 7.25 (d, 2H, Jˆ8.7 Hz), 4.57 (d, 1H, Jˆ8.3 Hz),
2.18±0.85 (m, 11H). 13C NMR: d 139.4, 133.6, 128.9,
128.5, 68.8, 45.6, 30.3, 30.1, 26.0, 25.8.
4.3.3. 1-(1-Chloropentyl)-4-chlorobenzene (5c). Colorless
1
liquid. H NMR: d 7.31 (dd, 4H, Jˆ3.3 Hz), 4.80 (t, 1H,
Jˆ7.2 Hz), 2.12±1.97 (m, 2H), 1.44±1.22 (m, 4H), 0.89 (t,
3H, Jˆ6.7 Hz). 13C NMR: d 140.5, 133.9, 128.7, 128.3,
62.8, 39.7, 29.1, 22.1, 13.9. HRMS: Calcd for C11H14Cl2
[M]1, 216.0473. Found: m/z, 216.0479. Anal. Calcd for
C11H14Cl2: C, 60.85; H, 6.50. Found: C, 60.96; H, 6.48.
4.3.12. 1-Chloro-2-(chloro-cyclohexyl-methyl)benzene
(5l). Colorless liquid. 1H NMR: d 7.58±7.15 (m, 4H),
5.24 (d, 1H, Jˆ8.1 Hz), 2.16±0.84 (m, 11H). 13C NMR: d

G. W. Kabalka et al. / Tetrahedron 58 (2002) 3243±3248
3247
138.6, 132.7, 129.5, 129.3, 128.8, 127.0, 64.6, 45.0, 30.1,
29.5, 26.1, 26.0, 25.8. HRMS: Calcd for C13H16Cl2 [M]1,
242.0629. Found: m/z, 242.0641. Anal. Calcd for C13H16Cl2:
C, 64.21; H, 6.63. Found: C, 64.30; H, 6.70.
19.3, 16.3, 15.5, 11.5, 10.7. HRMS: Calcd for C12H17Cl
[M]1, 190.102. Found: m/z, 190.101.
Acknowledgements
4.3.13. 1-Bromo-4-(chloro-cyclohexyl-methyl)benzene
(5m). Colorless liquid. 1H NMR: d 7.43 (d, 2H, Jˆ
8.4 Hz), 7.17 (d, 2H, Jˆ8.4 Hz), 5.54 (d, 1H, Jˆ8.2 Hz),
2.15±0.83 (m, 11H). 13C NMR: d 139.8, 131.4, 129.1,
121.7, 68.7, 45.5, 30.2, 30.0, 26.0, 25.8, 25.7. HRMS:
Calcd for C13H16BrCl [M]1, 288.0102. Found: m/z,
288.0114.
We wish to thank the US Department of Energy and the
Robert H. Cole Foundation for support of this research.
References
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4.3.14. 1-Bromo-3-(chloro-cyclohexyl-methyl)benzene
1
(5n). Colorless liquid. H NMR: d 7.48 (s, 1H), 7.43±7.17
(m, 3H), 4.54 (d, 1H, Jˆ8.2 Hz), 2.17±0.88 (m, 11H). 13C
NMR: d 143.2, 131.0, 130.6, 129.9, 126.2, 122.3, 68.6, 45.6,
30.4, 30.0, 26.0, 25.8. HRMS: Calcd for C13H16BrCl [M]1,
288.0102. Found: m/z, 288.0096.
4.3.15. 1-(Chloro-cyclohexyl-methyl)-4-¯uorobenzene
(5o). Colorless liquid. H NMR: d 7.32±7.24 (m, 2H),
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1
7.06±6.96 (m, 2H), 4.58 (d, 1H, Jˆ8.4 Hz), 2.20±0.84
(m, 11H). 13C NMR: d 164.2, 160.3, 136.8, 129.3, 129.1,
115.4, 115.0, 68.9, 45.8, 30.2, 26.1, 25.9. Anal. Calcd for
C13H16ClF: C, 68.87; H, 7.11. Found: C, 68.66; H, 7.14.
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4.3.16. 1,4-Di-(chloro-cyclohexyl-methyl)benzene (5p).
1
White solid. Mp 94±868C. H NMR: d 7.28 (s,4H), 4.60
(d, 2H, Jˆ8.2 Hz), 2.19±0.83 (m, 22H). 13C NMR: d 140.5,
127.4, 69.3, 45.6, 30.4, 30.1, 26.0, 25.9, 25.9. HRMS: Calcd
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4.3.17. (1-Chloro-2-methylbutyl)benzene (5q). Colorless
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1
Jˆ6.7 Hz), 4.70 (d, 0.45H, Jˆ8.0 Hz), 2.06±0.80 (m, 9H).
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69.3, 69.1, 42.9, 42.6, 26.8, 26.0, 16.1, 15.3, 11.4, 10.8.
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4.3.18.
1-Chloro-4-(1-chloro-2-methylbutyl)benzene
1
(5r). Colorless liquid. H NMR: d 7.31 (d, 2H, Jˆ8.8 Hz),
7.26 (d, 2H, Jˆ8.7 Hz), 4.78 (d, 0.45H, Jˆ6.6 Hz), 4.66
(d, 0.55H, Jˆ7.9 Hz), 2.01±0.79 (m, 9H). 13C NMR: d
39.7, 139.4, 133.6, 133.5, 129.0, 128.8, 128.5, 68.3,
68.1, 42.9, 42.6, 26.8, 25.9, 16.0, 15.2, 11.4, 10.8. Anal.
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4.3.19. 1-(1-Chloro-2-methylbutyl)-4-¯uorobenzene (5s).
Colorless liquid. 1H NMR: d 7.35±7.28 (m, 2H), 7.05±6.99
(m, 2H), 4.79 (d, 0.40H, Jˆ6.8 Hz), 4.68 (d, 0.60H,
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1
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