A Convenient Procedure for the Synthesis of Acetals from α-Halo Ketones

Article abstract of DOI:10.1002/1615-4169(200201)344:1<57::AID-ADSC57>3.0.CO;2-0

A study for determining the scope and limitations of a procedure for synthesising ethylene acetals from haloketones is presented. The method uses 1,2-bis(trimethylsilyloxy)ethane, BTSE, as reagent and Nafion-TMS as catalyst. Two procedures have been tested: (A) stoichiometric amounts of the haloketone and BTSE and a catalytic amount of Nafion-TMS were heated to reflux in chloro-form solution, and (B) stoichiometric amounts of the reactants and a catalytic amount of Nafion-TMS were heated to 90-100°C in the absence of solvent. The following ketones have been tested: 2-bromo-1-phenyl-1-ethanone, 2-bromo-cyclopentenone, 3-bromo-3-methyl-2-butanone, 3-chloro-3-methyl-2-butanone, 1-bromo-3,3-dimethyl-2-butanone, 1-chloro-3,3-dimethyl-2-butanone, 2-bromocyclohexanone, 2-chloro-1-cyclohexyl-1-ethanone, 1,1-dibromo-3,3-dimethyl-2-butanone, 1,3-dibromo-3-methyl-2-butanone, 1,3-dibromo-2-butanone, 1,3-dibromo-2-propanone, 2-chloro-1-phenyl-1-ethanone, and endo-2-bromocamphor. Yields were in the range 57-100% with the exceptions of endo-2-bromocamphor which afforded < 10% yield and the dibromoketones 1,1-dibromo-3,3-dimethyl-2-butanone and 1,3-dibromo-3-methyl-2-butanone for which the method failed. Factors determining the scope and limitations are briefly discussed. Full experimental details and spectroscopic data of the acetals are given.

Full text of DOI:10.1002/1615-4169(200201)344:1<57::AID-ADSC57>3.0.CO;2-0

FULL PAPERS
A Convenient Procedure for the Synthesis of Acetals from a-Halo Ketones
a,
b
a
Rolf Carlson, * Hanna Gautun, Andreas Westerlund
a
Department of Chemistry, Faculty of Science, University of Troms˘, 9037 Troms˘, Norway
Fax: ( ‡ 47)-776-44-765, e-mail: rolf.carlson@chem.uit.no
b
Department of Chemistry, Norwegian Institute of Science and Technology, 7491 Trondheim, Norway
Received September 1, 2001; Accepted November 6, 2001
Abstract: A study for determining the scope and limitations
of a procedure for synthesising ethylene acetals from
haloketones is presented. The method uses 1,2-bis(trime-
bromocyclohexanone,
2-chloro-1-cyclohexyl-1-ethanone,
1,1-dibromo-3,3-dimethyl-2-butanone, 1,3-dibromo-3-meth-
yl-2-butanone, 1,3-dibromo-2-butanone, 1,3-dibromo-2-
propanone, 2-chloro-1-phenyl-1-ethanone, and endo-2-bro-
mocamphor. Yields were in the range 57 ± 100% with the
exceptions of endo-2-bromocamphor which afforded <10%
yield and the dibromoketones 1,1-dibromo-3,3-dimethyl-2-
butanone and 1,3-dibromo-3-methyl-2-butanone for which
the method failed. Factors determining the scope and
limitations are briefly discussed. Full experimental details
and spectroscopic data of the acetals are given.
¾
thylsilyloxy)ethane, BTSE, as reagent and Nafion -TMS as
catalyst. Two procedures have been tested: (A) stoichio-
metric amounts of the haloketone and BTSE and a catalytic
¾
amount of Nafion -TMS were heated to reflux in chloro-
form solution, and (B) stoichiometric amounts of the
¾
reactants and a catalytic amount of Nafion -TMS were
heated to 90 ± 1008C in the absence of solvent. The
following ketones have been tested: 2-bromo-1-phenyl-1-
ethanone, 2-bromo-cyclopentenone, 3-bromo-3-methyl-2-
butanone, 3-chloro-3-methyl-2-butanone, 1-bromo-3,3-di-
methyl-2-butanone, 1-chloro-3,3-dimethyl-2-butanone, 2-
Keywords: acetals; 1,2-bis(trimethylsilyoxy)ethane; 1,3-di-
oxolanes; a-halo ketones; protecting group.
Introduction
tones have been found in the literature.[8] We have recently
used a modification of this method in which trimethylsilyl
triflate was replaced by the commercially available Nafion -
¾
Acetal protection of the carbonyl group is a common operation
and is mentioned in any textbook on organic chemistry. A
thorough compilation of methods for their preparation is given
by Green and Wuts.[ In our studies of functionalized
haloketones we needed an efficient procedure for the prepa-
ration of ethylene acetals from haloketones. A survey of the
vast literature on the synthesis of acetals showed that the
TMS, which is a polymeric perfluorosulfonic ester of trime-
thylsilanol.[ In the present paper we report that this method
can be used also for the preparation of ethylene acetals from
haloketones.
9]
1]
number of general methods for their preparation from Methods and Results
haloketones are remarkably few in number. It is not possible
to say whether this is due to a lack of interest in such
compounds or due to difficulties encountered in their prepa-
ration. Classical acid-catalyzed treatment with 1,2-ethanediol
has been used.[ One such example of this is given by the
Organic Synthesis procedure[ for the acid-catalyzed reaction
of 2-bromo-2-cyclopenten-1-one with 1,2-ethanediol which
required 64 h of reflux to afford 80% of the acetal. Attempts to
use microwave radiation to increase the rate of the reaction of
Haloketones
The haloketones 1 ±14 shown in Figure 1 were studied.
Ketones 1 ±11 were prepared by published procedures, see
the Experimental Section for references and physical data.
Ketones 12 ± 14 were obtained from commercial sources.
2]
3a]
haloketones with 1,2-ethanediol have also been reported.[4]
A
Acetal Formation
paper describing a method which uses a combination of 1,2-
ethanediol and chlorotrimethylsilane also reported the for-
mation of the ethylene acetal from a-chloroacetophenone.[
However, the use of acidic conditions and long reaction time is
not recommended for reactions involving haloketones since
these compounds may rearrange to yield mixtures of isomeric
haloketones in acid medium.[6] A promising method for
ethylene acetal synthesis under neutral conditions involves
the reaction of carbonyl compounds with 1,2-bis(trimethylsi-
We have used two variants of the procedure. Method A: For
5]
sterically unhindered haloketones, stoichiometric amounts of
¾
haloketone and BTSE and a catalytic amount of Nafion -TMS
were heated in refluxing chloroform solution until all starting
ketone was consumed. Method B: For sterically crowded
ketones and dihaloketones, the reactants were heated to 90 ±
1008C without solvent. The yields obtained are summarized in
Table 1 and refer to isolated yields of purified product (>95%
pure, GC) after Kugelrohr distillation or flash chromatography
lyloxy)ethane, BTSE, in the presence of trimethylsilyl tri-
flate.[ Two examples of the use of this method with haloke- on silica gel. The reactions were monitored by gas chromatog-
7]
Adv. Synth. Catal. 2002, 344, No. 1
¹ VCH Verlagsgesellschaft mbH, D-69451 Weinheim, 2002 1615-4150/02/34401-057 ± 060 $ 17.50+.50/0
57

FULL PAPERS
Rolf Carlson et al.
monohaloketones in the study to determine whether or not
steric effects would inhibit the reaction and thereby limit the
scope of the method. The low yield of acetal from bromocam-
phor shows that severe crowding limits the reaction. 1-Bromo-
3
,3-dimethyl-2-butanone (5) and 1-chloro-3,3-dimethyl-2-bu-
tanone (6) afford good yields showing that moderate steric
hindrance does not reduce the utility of the reaction. For the
dibromoketones, 1,3-dibromo-2-butanone (11) and 1,3-dibro-
mopropanone (12), the reaction affords good yields. However,
the reaction time increases considerably going from 12 to 11.
With 1,3-dibromo-3-methyl-2-butanone (10) and 1,1-dibromo-
3
,3-dimethyl-2-butanone (9) the method failed. We interpret
this largely to be due to the effect of increasing steric
hindrance. However, the bromo substituent is isosteric with a
methyl group and the observation that 1,1-dibromo-3,3-
dimethyl-2-butanone (9) affords good yields but 1,3-dibro-
mo-3-methyl-2-butanone (10) fails indicate that there is also an
electronic component involved. Chan, Brook and Chaly[
claim that the presence of a halogen substituent alpha to the
carbonyl facilitates acetal formation in the procedure when
using ethylene glycol and chlorotrimethylsilane. We do not
agree with this interpretation and our findings contradict the
statement by these authors. Our arguments follow from the
tentative mechanism for the conversion of ketones to acetals in
the presence of BTSE and chlorotrimethylsilane which is
sketched in Scheme 1. This mechanism is very similar to the
mechanism proposed in Ref.[
5]
Figure 1. Haloketones investigated.
Table 1. Yields of acetals.
Starting ketone
Method
Reaction time [h]
Yield [%]
1
1
2
2
3
4
5
5
6
6
7
8
9
9
A
B
A
B
A
A
B
A
A
B
A
A
A
B
A
B
B
B
B
B
22
4
10
5
94
>99
60
57[
73
74
85
100
84
90
97
68
0
5]
a]
If the mechanism in Scheme 1 is correct, an electron-
withdrawing a-halo substituent should strongly disfavour the
formation of charged intermediates due to severe dipole-
dipole repulsion. Hence, one a-halo substituent disfavours
acetal formation and two a-halogens may inhibit the reaction.
49
20
23
68
68
17
21
67
120
72
404
40
89
9
0
0
0
1
1
1
1
1
1
0
0
1
2
3
4
90
89
99
<10[
5
93
b]
[
a]
Decomposes.
[
b]
The product was not isolated, the identity was inferred from its mass
spectrum.
raphy and were interrupted when all starting material had
disappeared or when there was no further increase in the
amount of acetal formed. In the latter case, the pure acetal was
Scheme 1.
obtained by flash chromatography. The identities of the
1
products were inferred from their mass spectrum, H and Conclusions
13
C NMR spectra, and IR spectrum.
The method described in this paper offers a procedure for
preparing ethylene acetals from a-haloketones under neutral
conditions. This is an advantage since a-haloketones are prone
to rearrange under acidic conditions. The method affords good
to excellent yields with moderately congested monohaloke-
tones. With sterically hindered dihaloketones, the methods
fails.
Discussion
The results show that the present method can be used for the
synthesis of ethylene acetals from monohaloketones under
almostneutral conditions. We have included sterically crowded
5
8
Adv. Synth. Catal. 2002, 344, 57 ±60

A Convenient Procedure for the Synthesis of Acetals from a-Halo Ketones
FULL PAPERS
[
12]
mide analogous to the procedure given by Rappe and Kumar. Bp of 3: 40 ±
Experimental Section
28C/17 torr (Lit.[ 408C/17 torr); bp of 7: 84 ±868C/15 torr (Lit. 688C/
12]
[13]
4
2
torr).
Spectroscopic Methods
3
-Chloro-3-methyl-2-butanone (4) was obtained by chlorination of the
parent ketone with sulfuryl chloride according to Wyman and Kaufman.
The pure ketone was obtained by spinning band distillation; bp 113 ± 1148C
[
14]
1H and 13C NMR spectra were recorded in deuteriochloroform with TMS as
internal reference on a Jeol JNM-EX400 spectrometer operating at
(Lit.[ 143 ± 1458C).
14]
1
13
4
00 MHz ( H) and 100 MHz ( C). Mass spectra were taken via gas
1-Bromo-3,3-dimethyl-2-butanone (5) and 1,1-dibromo-3,3-dimethyl-2-
butanone (9) were prepared by bromination of the parent ketone according
to Ramasseul and Rassat.[ Ketone 5 was purified by fractionation over a
Vidmer column, bp 1078C/80 torr (Lit.[ 72 ± 748C/10 torr). Ketone 9 was
recrystallized from ethanol, mp 73 ± 748C (Lit.[ 748C).
chromatograph on a VG Quattro or a VG Tribrid instrument. Electron
impact ionization (70 eV, 1808C ion source) was used. In the reported
spectra, mass fragments under 5% relative abundance are not included. The
mass spectra are reported as follows: m/z (relative abundance in %)
15]
15]
15]
[
assignment]. IR spectra were recorded as neat film between NaCl plates
1-Chloro-3,3-dimethyl-2-butanone (6) and 2-chloro-1-cyclohexyl-1-etha-
none (8) were prepared by halogenation of the morpholine enamine of the
using a Perkin Elmer 1600 Series FT-IR instrument.
parent ketone according to Carlson.[ Bp of 6: 83 ±858C/10 torr (Lit.
16]
[17]
108C/14 torr), bp of 8: 98 ± 1008C/10 torr (Lit.[ 1108C/14 torr).
18]
1
1
,3-Dibromo-3-methyl-2-butanone (10) and 1,3-dibromo-2-butanone
11) were obtained by bromination of the parent ketones in chloroform
solution. The pure ketones were obtained by fractionation over a Vidmer
Gas Chromatography
(
[
19]
A CP-Sil-8 CB open tubular column (0.32 mm i.d.) was used with helium as
carrier gas, flow rate 1.5 mL/min. A Varian 3300 gas chromatograph
equipped with a FID; injector temperature 2508C, detector temperature
column; bp of 10: 82 ±848C/10 torr (Lit.
86 ± 888C/12 torr), bp of 11:
1038C/50 torr (Lit.[ 64 ± 658C/2.3 torr).
20]
1,3-Dibromo-2-propanone (12) was obtained from Lancaster Ltd., 2-
chloro-1-phenyl-1-ethanone (13), was obtained from Fluka and endo-2-
bromocamphor (14) was obtained from Aldrich.
3
008C. Chromatograms were recorded on a Varian 4400 integrator. For
monitoring the reactions, chromatograms were generally taken isothermally
at 1208C, with exception of reactions run with 3-chloro-3-methyl-2-
butanone, when a program 408C/2 min, 208C/min, 1208C was used.
Acetal Synthesis
Chemicals
The reactions were run using 10.0 mmol of the haloketone.
Method A: A 25-mL, round-bottomed flask was mounted with a reflux
condenser with a drying tube. The flask was charged with haloketone
(10.0 mmol) and BTSE (2.06 g, 10.0 mmol) dissolved in 10 mL of chloro-
2 2 3
Solvents (CH Cl and CHCl ) were pro analysi qualities and supplied from
Merck and used as delivered. 1,2-Ethanediol puriss. from Fluka was used as
¾
delivered. Chlorotrimethysilane from Fluka was distilled. The haloketones
form. The catalyst, Nafion -TMS (50 mg), was added and the mixture was
¾
were prepared by published procedures, see below. The Nafion -TMS
magnetically stirred and heated to reflux. Samples were taken at time
intervals and analyzed by GC. The heating was discontinued when all
starting ketone was consumed or when there was no further increase in yield
of acetal. The reaction mixture was transferred into a clean flask by using a
Pasteur pipette. The solvent was evaporated under reduced pressure and the
residue was distilled using a Kugelrohr apparatus.
catalyst was obtained from Aldrich and used as delivered.
Melting points and boiling points are uncorrected.
1,2-Bis(trimethylsilyloxy)ethane, BTSE
Method B: A 10-mL, round-bottomed flask was equipped with an air
condenser mounted with a drying tube. The flask was charged with
A slightly modified literature procedure[10] was used. A 500-mL, three-
necked Erlenmeyer flask was charged with 1,2-ethanediol (25 mL, 0.44 mol)
and chlorotrimethylsilane (230 mL; a large excess). The flask was fitted with
a gas inlet and a reflux condenser coupled to a trap for hydrogen chloride via
a moisture protective tube with calcium chloride. The resulting two-phase
system was magnetically stirred and heated to reflux while a slow stream of
dry nitrogen was led through the flask. The reflux was maintained for 50 h
during which time the reaction mixture became homogeneous. The reflux
condenser was replaced by a 20-cm Vigreux column and unreacted
haloketone (10.0 mmol), BTSE (2.06 g, 10.0 mmol) and Nafion -TMS
¾
(50 mg). The mixture was magnetically stirred and the flask was placed in
an oil bath heated to 90 ± 958C. Samples (one drop), taken at time intervals,
were diluted with dichloromethane and analyzed by GC. The work-up
procedure was as above with the exception that the reaction flask was rinsed
with three 1-mL portions of dichloromethane which were combined with the
crude product prior to evaporation and Kugelrohr distillation.
chlorotrimethylsilane was removed by distillation. BTSE was collected at
1
Physical and Spectral Properties of the Acetals
1
60 ± 1688C; yield: 74.6 g (82%); H NMR: d ˆ 0.10 (18H, s), 3.61 (4H, s);
C NMR: d ˆ 0.4, 63.9; MS: no molecule ion was observed, m/z ˆ 193 (10),
1
3
‡
1
92 (24) 191 (57) [M -CH3], 150 (5), 149 (39), 147 (100) 134 (5), 132 (43), 131
2-Phenyl-2-bromomethyl-1,3-dioxolane (acetal from 1): colourless oil, bp
‡
[2a]
(
28), 117 (9), 115 (10), 105 (8), 104 (11), 103 (48), 101 (12), 89 (8)[Me
3
SiO ],
1308C/12 torr, solidifies on standing, mp 60 ± 618C, (Lit. mp 60 ± 618C ).
‡
1
8
8 (17), 87 (6), 75 (30), 74 (29), 73 (57) [Me
3
Si ], 67 (10), 66 (34), 61 (9), 60 (5),
H NMR: d ˆ 3.67 (2H, s), 3.84 ± 3.95 (2H, m), 4.13 ± 4.24 (2H, m), 7.31 ± 7.40
1
3
5
9 (30), 58 (14), 52 (11), 47 (11), 45 (29), 44 (14), 43 (25).
(3H, m), 7.44 ± 7.57 (2H, m); C NMR: d ˆ 38.2, 65.9, 107.3, 126.0, 128.4,
1
28.9, 139.7.
-Bromo-6,9-dioxa-spiro[4.4]non-2-ene (acetal from 2): colourless oil, bp
2
[
3a]
1
4
2
3
88C/ 0.5 mbar (Lit. 65 ± 658C/0.7 torr). H NMR: d ˆ 2.14 ± 2.18 (2H, m),
.34 ± 2.38 (2H, m), 3.97 ± 4.02 (2H, m), 4.15 ± 4.20 (2H, m), 6.17 (1H, dd, J ˆ
Haloketones
1
3
.2 Hz, J ˆ 2.6 Hz); C NMR: d ˆ 28.7, 34.4, 66.0, 117.7, 123.9, 136.7
2
-Bromo-1-phenyl-1-ethanone (1) was prepared by bromination of aceto-
2-(1-Bromo-1-methyl-ethyl)-2-methyl-1,3-dioxolane (acetal from 3): col-
1
phenone in the presence of aluminium trichloride according to Cowper and
ourless oil, bp 58 ± 628C/14 torr. H NMR: d ˆ 1.50 (3H, s), 1.77 (6H, s), 4.03
[
11]
[11]
13
Davidson. It was recrystallized from ethanol, mp 49 ± 508C (Lit. 49 ±
18C).
-Bromo-2-cyclopentene-1-one (2) was prepared from 2-cyclopenten-1-
(4H, s); C NMR: d ˆ 20.6, 29.6, 66.0, 70.1, 112.0. MS: (no molecule ion was
‡
5
observed), m/z ˆ 195 (5), 193 (6) [M À CH
3
], 129 (14), 114 (17), 113 (7), 99
2
(11), 88 (7), 87 (100), 69 (11), 57 (16), 45 (6), 43 (60), 42 (6), 41 (22). IR: nmax
ˆ
[
3a]
one according to Smith III et al. It was recrystallized from hexane, mp
5.2 ± 35.78C (Lit. 36 ± 378C, Lit. 39 ± 39.58C).
-Bromo-3-methyl-2-butanone (3) and 2-bromocyclohexanone (7) were
2986, 2884, 1454, 1372, 1260, 1217, 1159, 1137, 1092, 1043, 950, 894, 881, 771,
[
3a]
[3b]
À1
3
648, 590 cm . HRMS: No molecule ion was observed. High-resolution mass
‡
3
determination was made using the [M À CH
3
] ion. Observed: 194.984091
synthesized from the parent ketone by bromination with N-bromosuccini-
6 2
and 192.987014; C H10BrO requires 194.984370 and 192.986416.
Adv. Synth. Catal. 2002, 344, 57 ±60
59

FULL PAPERS
Rolf Carlson et al.
‡
‡
2
-(1-Chloro-1-methyl-ethyl)-2-methyl-1,3-dioxolane (acetal from 4): col-
observed, m/z ˆ 261 (24) 259, (24) [M À CH
3
], 197 (21), 195 (100) [M À
1
ourless oil, bp 51 ± 538C/12 torr. H NMR: d ˆ 1.45 (3H, s), 1.59 (6H, s), 4.02
Br], 180 (8), 179 (33), 167 (20), 166 (36), 165 (14), 164 (35), 156 (24), 155 (36),
153 (6), 151 (22), 149 (6), 142 (26), 141 (37), 140 (26), 139 (32), 138 (26), 137
(6), 135 (19), 134 (5), 133 (28), 132 (9), 127 (25), 126 (26), 125 (32), 123 (29),
122 (25), 121 (32), 120 (26), 119 (26), 117 (8), 115 (14), 114 (26), 112 (67), 111
(18), 110 (15), 109 (33), 108 (22), 107 (33), 106 (17), 105 (31), 103 (13), 100 (6),
99 (31), 98 (6), 97 (30), 96 (13), 95 (36), 94 (13), 93 (33), 92 (21), 91 (37), 89 (6),
87 (27), 86 (14), 85 (7), 84 (21), 83 (34), 82 (26), 81 (31), 80 (24), 79 (33), 78
(24), 77 (31), 74 (7), 73 (31), 70 (16), 69 (30), 68 (29), 67 (30), 66 (26), 65 (28),
64 (7), 63 (18), 59 (7), 58 (5), 57 (19), 56 (22), 55 (29), 54 (24), 53 (26), 52 (23),
51 (24), 50 (13), 45 (24), 44 (22), 43 (26), 42 (23), 41 (26).
(
4H, s); 13C NMR: d ˆ 20.2, 28.0, 66.0, 73.8, 112.0. MS: No molecule ion was
‡
observed, m/z ˆ 151 (11), 149 (33) [M À CH
3
], 129 (19), 113 (15), 88 (20), 87
(
(
1
100), 85 (8), 79 (8), 77 (21), 73 (9), 69 (14), 67 (15), 57 (28), 53 (8), 45 (11), 44
6) 43 (64) 42 (10), 41 (34). IR: nmax ˆ 2984, 2886, 1454, 1371, 1253, 1219, 1164,
À1
095, 1045, 950, 887, 846, 774, 674, 600 cm . HRMS: No molecule ion was
‡
observed. High-resolution mass determination was made using the [M À
CH
3 6 2
] ion. Observed: 151.033243 and 149.036296; C H10ClO requires
1
51.033982 and 149.036932.
2
-(1,1-Dimethylethyl)-2-bromomethyl-1,3-dioxolane (acetal from 5): col-
1
ourless oil, bp 55 ± 578C/12 torr. H NMR: d ˆ 1.21 (9H, s), 3.72 (2H, s),
1
3
3
1
1
4
1
.95 ± 4.07 (2H, m), 4.26 ± 4.37 (2H, m); C NMR: d ˆ 25.8, 38.1, 40.6, 67.7,
‡
13.0. MS: No molecule ion was observed, m/z ˆ 209 (3), 207 (3) [M À CH
3
],
67 (96), 165 (100), 129 (51), 122 (20), 121 (20) 86 (31) 73 (8), 57 (24), 55 (7),
Acknowledgements
3 (13), 42 (12), 41 (18). IR: nmax ˆ 2965, 2898, 1478, 1414, 1365, 1246, 1171,
À1
063, 1042, 982, 955, 823, 674 cm . HRMS: No molecule ion was observed.
We thank Professor Einar Uggerud at the University of Oslo for running the
high resolution mass spectra and Professor Ed Hough for linguistic
assistance. We also thank the Norwegian Research Council for generous
financial support.
‡
High-resolution mass determination was made using the [M À CH
3
] ion.
Observed: 208.999646 and 207.001291; C
07.002066.
7 2
H12BrO requires 209.000020 and
2
2
-(1,1-Dimethylethyl)-2-chloromethyl-1,3-dioxolane (acetal from 6): col-
1
ourless oil, bp 73 ± 758C/12 torr. H NMR: d ˆ 1.20 (9H, s), 3.80 (2H, s),
1
3
3
1
1
.96 ± 4.07 (2H, m), 4.23 ± 4.33 (2H, m); C NMR: d ˆ 25.7, 40.2, 48.5, 67.7,
‡
References
13.2. MS: No molecule ion was observed, m/z ˆ 165 (3), 163 (9) [M À CH
3
],
30 (10), 129 (88), 123 (76), 122 (13), 121 (100), 99 (5), 86 (14), 79 (13), 77
(
n
36), 73 (12), 57 (35), 55 (9), 51 (6), 49 (13), 45 (9), 43 (12), 42 (11), 41 (23). IR:
[1] T. W. Greene, P. G. M. Wuts, Protective Groups in Organic Synthesis,
3rd Edn., Wiley-Interscience, New York, 1999, Chap. 4.
[2] A. Kuehn, J. Prakt. Chem. 1940 156, 103; A. Kumar, R. A. Rane,
V. K. Ravindran, S. Y. Dike, Synth. Commun. 1997, 27, 1183.
[3] A. B. Smith III, S. J. Branco, M. A. Guaciao, P. M. Wovkulich, A.
Korn, Org. Synth. 1983, 61, 65; E. W. Garbisch Jr, J. Org. Chem. 1965,
30, 2109.
max ˆ 2964, 2900, 1480, 1422, 1393, 1366, 1172, 1065, 1018, 995, 955, 844, 746
À1
cm . HRMS: No molecule ion was observed. High-resolution mass
‡
‡
determination was made using the [M À CH
3
] and [M À C(CH
3 3
) ] ions.
7 2
Observed: 165.050454 and 163.052189; C H12ClO requires 165.049632 and
1
1
63.052582. Observed: 123.002849 and 121.005229; C
23.002682 and 121.005632.
4 6 2
H ClO requires
6
-Bromo-2,5-dioxa-spiro[4.5]decane (acetal from 7): colourless oil, bp
[4] M. Moghaddam, F. Sharifi, Synth. Commun. 1995, 25, 2457.
[5] T. H. Chan, M. A. Brook, T. Chaly, Synthesis 1983, 203.
[6] M. D. Metha, D. Miller, J. D. Tidy, J. Chem. Soc. 1963, 4614; E.
Warnhoff, M. Rampersad, P. Sundara Raman, F. W. Yerhoff, Tetra-
hedron Lett. 1978, 32, 1659.
[
20]
1
1
(
4
6
12 ± 1168C/12 torr (Lit.
1H, m), 1.46 ± 1.73 (4H, m), 1.95 ± 2.08 (2H, m), 2.15 ± 2.25 (1H, m), 3.91 ±
90.5 ± 92.58C/5 torr). H NMR: d ˆ 1.30 ± 1.42
1
3
.02 (2H, m), 4.05 ± 4.18 (3H, m); C NMR: d ˆ 23.2, 24.1, 34.2, 35.0, 57.2,
5.6, 65,7, 108.0
2
-Chloromethyl-2-cyclohexyl-1,3-dioxolane (acetal from 8): colourless
[7] T. Tsunoda, M. Suzuki, R. Noyori,Tetrahedron Lett. 1980, 21, 1357; S.
Morata, R. Noyori, Tetrahedron Lett. 1980, 21, 767.
[8] M. A. Tius, G. S. K. Kannangara, Tetrahedron 1992, 48, 9173; E. A.
Mash, S. B. Hemperty, K. A. Nelson, P. C. Heidt, S. Ven Deusen, J.
Org. Chem. 1990, 55, 2045.
[9] A. Westerlund, R. Carlson, Synth. Commun. 1999, 29, 4035.
[10] A. E. Pierce, Silylation of Organic Compounds, A Technique for Gas-
Phase Analysis. Pierce Chemical Co., Rockford, Ill. 1968, pp. 18 and
24.
[11] R. M. Cowper, L. H. Davidson, Org. Synth. Coll. Vol. II, 1943, p. 480.
[12] C. Rappe, R. Kumar, Ark. Kemi 1965, 23, 475.
[13] P. C. Purohit, H. R. Sonawane, Tetrahedron 1981, 37, 873.
[14] D. P. Wyman, P. R. Kaufman, J. Org. Chem. 1964, 29, 1956.
[15] R. Ramasseul, A. Rassat, Bull. Soc. Chim. Fr. 1963, 2214.
[16] R. Carlson, Acta Chem. Scand. Ser. 1978, 32, 646.
[17] J. Villieras, C. Bacquet, J. F. Normant, J. Organometal. Chem. 1975,
97, 355.
[18] S. Sarel, M. S. Newman, J. Am. Chem. Soc. 1956, 78, 5416.
[19] N. de Kimpe, L. D×Hondt, L. Moens, Tetrahedron 1992, 48, 3183.
[20] E. W. Garbish Jr, J. Org. Chem. 1964, 29, 2109.
1
oil, bp 100 ± 1058C/12 torr. H NMR: d ˆ 1.06 ± 1.20 (6H, m), 1.75 ± 1.89 (5H,
1
3
m), 3.52 (2H, s), 3.93 ± 3.99 (2H, m), 4.01 ± 4.07 (2H, m); C NMR: d ˆ 26.2,
2
(
7
6.3, 26.6, 28.5, 66.2, 111.0. MS: No molecule ion was observed, m/z ˆ 156
‡
‡
6), 155 (70) [M À CH
2
Cl], 123 (42), 121 (100) [M À C
6
H11], 83 (12), 79 (9),
‡
7 (18), 73 (10), 55 (21), 51 (4), 49 (7) [CH
2
Cl ], 43 (6), 42 (5), 41 (17). HRMS
could not be obtained since the substance decomposed during transporta-
tion.
2
-(1-Bromoethyl)-2-bromomethyl-1,3-dioxolane (acetal from 11): col-
[
21]
1
ourless oil, bp 115 ± 1188C/12 torr (Lit. 118 ± 1298C/12 torr). H NMR:
d ˆ 1.69 (3H, d, J ˆ 7.3 Hz), 3.57 (1H, d, J ˆ 11.7 Hz), 3.79 (1H, d, J ˆ
1
3
1
1.7 Hz), 4.45 (1H, q, J ˆ 7.3 Hz); C NMR: d ˆ 20.2, 34.5, 50.0, 67.1, 108.6.
2
,2-Bis(bromomethyl)-1,3-dioxolane (acetal from 12): colourless oil, bp
[
2a]
1
1
4
07 ± 1108C/12 torr (Lit. bp 1138C/16 torr). H NMR: d ˆ 3.59 (4H, s),
.12 (4H, s); 13C NMR: d ˆ 33.7, 66.7, 106.7.
2
-Chloromethyl-2-phenyl-1,3-dioxolane (acetal from 13): colourless oil,
bp 1288C/15 torr, solidifies on standing, mp (from MeOH) 63.6 ± 64.18C
[
5]
1
(
Lit. 908C). H NMR: d ˆ 3.75 (2H, s), 3.92 (2H, m), 4.18 (2H, m), 7.37 (3H,
1
3
m), 7.51 (2H, m); C NMR: d ˆ 49.5, 65.9, 107.9, 126.1, 128.4, 129.9, 139.8.
Ethylene acetal from endo-2-bromocamphor: the compound was identi-
fied from its mass spectrum. It was not isolated. MS: no molecule ion was
[21] J. Gelas, S. Michaud, Bull. Soc. Chim. Fr. 1972, 2445.
6
0
Adv. Synth. Catal. 2002, 344, 57 ±60