Acetonyltriphenylphosphonium bromide and its polymer-supported analogues as catalysts for the protection of carbonyl compounds as acetals or thioacetals

Article abstract of DOI:10.1081/SCC-120022172

Both acetonyltriphenylphosphonium bromide (ATPB) and poly-p-styryldiphenylacetonylphosphonium bromide (PATPB) are excellent catalysts in the protection of aldehydes as acetals or thioacetals. In general, ATPB is highly selective as ketones do not give good yields of ketals with this catalyst.

Full text of DOI:10.1081/SCC-120022172

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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 16, pp. 2829–2842, 2003
Acetonyltriphenylphosphonium Bromide and
Its Polymer-Supported Analogues as Catalysts
for the Protection of Carbonyl Compounds
as Acetals or Thioacetals
1
Yung-Son Hon,1,2, Chia-Fu Lee,
*
Rong-Jiunn Chen,1 and Yi-Fen Huang1
1Department of Chemistry and Biochemistry, National
Chung Cheng University, Chia-Yi, Taiwan, R.O.C.
2Institute of Chemistry, Academia Sinica,
Nankang, Taipei, Taiwan, R.O.C.
ABSTRACT
Both acetonyltriphenylphosphonium bromide (ATPB) and poly-
p-styryldiphenylacetonylphosphonium bromide (PATPB) are excel-
lent catalysts in the protection of aldehydes as acetals or thioacetals.
In general, ATPB is highly selective as ketones do not give good
yields of ketals with this catalyst.
*Correspondence: Yung-Son Hon, Department of Chemistry and Biochemistry,
National Chung Cheng University, Chia-Yi, Taiwan, 621, R.O.C.; Institute of
Chemistry, Academia Sinica, Nankang, Taipei, Taiwan 115, R.O.C.; Fax: 886-5-
2721040; E-mail: cheysh@ccu.edu.tw.
2829
DOI: 10.1081/SCC-120022172
Copyright & 2003 by Marcel Dekker, Inc.
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2830
Hon et al.
Key Words: Acetonyltriphenylphosphonium bromide; Poly-p-
styryldiphenylacetonylphosphonium bromide; Acetals; Thioacetals.
INTRODUCTION
The most useful protective groups for carbonyl groups are
acetals and thioacetals. The synthesis of acetals orthioacetal form
aldehydes and ketones is carried out by different methods depending on
the case.[1] In the study of this reaction, particular attention was given to
the selection of catalysts, ranging from conventional acids (sulfuric acid,
ethanolic hydrochloric acid, p-toluenesulfonic acid, pyridinium p-
toluenesulfonate, ferric chloride, etc.), to acidic resins such as, amberlyst-
15 oracidic Montmorillonite clay K-10, [2,3] and finally to solid superacids,
Nafion-H type.[4] Recently, many heterogeneous catalytic systems such as
SOCl2-SiO2,[5] HY zeolite,[6] Mg-ZnTf,[7] natural kaolinitic clay[8] and
modified clays such as Mont-KSH[9] and Ce-Mont[10] have been
developed for such synthetic transformations.
We have reported the catalytic activity of acetonyltriphenylphos-
phonium bromide (ATPB) in the protection of alcohols with alkyl
vinyl ethers and their deprotection.[11] It can also be employed to
induce the cyclotrimerization of the aliphatic aldehydes.[12] ATPB can
be easily prepared from triphenylphosphine and bromoacetone in
benzene at room temperature in excellent yield.[11–13] It is crystalline
(C21H20BrOP, FW 399.27, m.p. 221–223ꢀC), nonhydroscopic, and
soluble in CH2Cl2, CHCl3, MeOH, EtOH, CH3CN but not in THF,
Et2O, benzene, and EtOAc.
+
+
-
-
PPh2CH2COMe Br
PPh2CH2COMe Br
PATPB
ATPB
Intrigued by ATPB’s peculiar catalytic activity described above,
we anchored the ATPB moiety on the cross-linked polystyrene back-
bone for practical purposes. This is primarily because insoluble
polymeric reagents, among other features, expand the range of applicable
solvents, increase the ease of work-up and product purification, lower
the environmental hazards, and in most cases provide for recovery
and regeneration of the supported reagents. We found that the
poly-p-styryldiphenylacetonylphosphonium bromide (PATPB) is also a
very efficient and excellent catalyst for the above mentioned reactions.[14]

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Acetonyltriphenylphosphonium Bromide
2831
In continuation of our efforts to explore its synthetic applications further,
herein we report the catalytic activities of ATPB and PATPB in the
formation of acetals and thioacetals from the corresponding carbonyl
compounds.
RESULTS AND DISCUSSION
ATPB as a Catalyst in the Protection of Aldehydes
as Acetal or Thioacetal
We have investigated the protection of aldehydes with alcohol in
the presence of ATPB. To a solution of 3-phenylpropanal (1) (287 mg,
2.14 mmol) in 2 mL of methanol was added ATPB (85 mg, 0.21 mmol)
and the solution was stirred at RT. The reaction was complete in 20 min.
The desired product 1a was obtained in 93% yield (Sch. 1; Entry 1,
Table 1). Undersimilarcondition, 3-phenylporpanal ( 1) reacted with
isopropanol to give the corresponding acetals in 65% yield after stirring
at room temperature for 24 h (Entry 3). The lower yield and longer
reaction time observed in the case of isopropanol shows that there is a
steric problem associated with the bulky isopropoxy group in the
protection of aldehyde. It is not surprising that 3-phenylpropanal (1)
does not react with tert-butanol at all.
The protection of aldehydes with diols was also investigated. In the
presence 0.1 mol equiv. of ATPB, 3-phenylpropanal (1) reacted with ethy-
lene glycol and 1,3-propanediol, respectively, to give the corresponding
acetals in excellent yields in 1 h (Entries 5, 7).
Underthe catalysis of ATPB, the a,a-disubstituted aldehyde such as
cyclohexanecarboxaldehyde (2) could react with methanol, ethylene
glycol, and 1,3-propanediol, respectively, to give the corresponding
2
2
R OH
R SH
R1CH(OR2)2
R1CH(SR2)2
R1CHO
Catalyst
Catalyst
R1 = -CH2CH2Ph 1
R1 = -CH2CH2Ph, R2=Me 1a
R1 = -CH2CH2Ph, R2=Et 1e
1 =Cyclohexyl, R2=Et 2e
R
1 = -CH2CH2Ph, R2=i-Pr 1b
1 =Cyclohexyl, R2=Me 2a
R
Cyclohexyl
2
R
R1 =Cyclohexyl, R2=i-Pr 2b
R1
S
R1
H
O
HS(CH )nSH
2
HO(CH )nOH
2
( )n
( )n
H
S
1 = -CH2CH2Ph, n=3 1f
1 =Cyclohexyl, n=3 2f
Catalyst
Catalyst
O
R1 = -CH2CH2Ph, n=2 1c
R
Catalyst = ATPB
or PATPB
1 = -CH2CH2Ph, n=3 1d
1 =Cyclohexyl, n=2 2c
R1 =Cyclohexyl, n=3 2d
R
R
R
Scheme 1.

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2832
Hon et al.
Table 1. The reaction of aldehyde with alcohol or thiol in the presence of ATPB
catalysts at room temperature.
ATPB
(mol
Acetal
or
equiv.) (h) thiacetal (%)
(mol Time
Yieldb
Entry R1CHO R1 ¼ equiv.)
Alcohol
MeOH
MeOH
a
1
2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
1
1
1
1
1
1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
–
–
–
–
1/3
1/6
24
1a
2a
1b
2b
1c
2c
1d
2d
1e
2e
1f
93
90
65
15c
92
88
91
92
90
89
83
81
a
a
a
3
i-PrOH
i-PrOH
4
24
5
HO(CH2)2OH
HO(CH2)2OH
HO(CH2)3OH
HO(CH2)3OH
EtSH
2
3/4
2/3
1
6
2
2
2
3
3
2
2
7
8
5/6
1/2
1/4
1/2
2/3
9
10
11
12
EtSH
HS(CH2)2SH
HS(CH2)3SH
2f
aAlcohol was used as solvent.
bIsolated yields.
cAbout 80% of the aldehyde 2 was recovered.
acetals in excellent yields (Entries 2, 6, 8, Table 1). All these reactions
completed within 1 h at RT. However, aldehyde 2 reacted sluggishly with
isopropanol to afford the corresponding acetal in only about 15% yield.
We recovered most of the aldehyde 2 (Entry 4).
ATPB is also effective in the protection of aldehydes with
mercaptans. In the presence 0.1 mol equiv. of ATPB, both aldehydes 1
and 2 reacted with ethanethiol (5 mol equiv.) to give the corresponding
dithioacetals 1e and 2e, respectively in excellent yields (Entries 9
and 10, Table 1). Similarly, both aldehydes 1 and 2 reacted with 1,3-
propanedithiol to give the corresponding dithioacetals 1f and 2f, respec-
tively in excellent yields (Entries 11 and 12, Table 1; Eq. (1)). All these
reactions completed within 1 h at RT. Interestingly, we isolated a small
amount of dithiol 1f 0 and 2f 0 in each of these two reactions (Eq. (1)).
cat.
S
S
S
S
SH
SH
ATPB
R1CHO + HS(CH2)3SH
R1
R1
+
(1)
1
R
= PhCH CH - 1
2 2
1
1f (83%)
1f (81%)
R
= Cyclohexyl 2
1f' (6%)
1f' (7%)

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Acetonyltriphenylphosphonium Bromide
2833
We wish to investigate the catalytic activity of ATPB in the pro-
tection of ketones. We found that when cyclohexanone (3) was treated
with 3 mol equiv. of ethylene glycol or2,2-dimethyl-1,3-porpanediol in
the presence of catalytic amount of ATPB in dichloromethane, the
1,3-dioxane 3a and 1,3-dioxolane 3b could be isolated in 75% and 92%
yields, respectively (Eq. 2). Under similar reaction conditions, we could
not form ketals from a-tetralone (4) with eitherethylene glycol or
2,2-dimethyl-1,3-propanediol. However, acyclic ketones such as aceto-
phenone (5) or4-phenyl-2-butanone ( 6) reacted with ethylene glycol or
2,2-dimethyl-1,3-propanediol to give less than 20% conversion of the
ketals. Attempts to improve the yield of the ketals by increasing the
reaction temperature and prolonging the reaction time did not produce
the expected results. In general, ATPB might not be a good catalyst in the
protection of ketones as ketals. This is indicative of its selectivity in
forming acetals from aldehydes.
R1OH, CH2Cl2
OR1
O
(2)
Cat. ATPB,
2 h
OR1
3
1
1
R , R =-CH CH -
3a 75%
2
2
1
1
R , R =-CH C(Me) CH - 3b 92%
2
2
2
PATPB as a Catalyst in the Protection of Aldehyde
as Acetal or Thioacetal
A copolymerof styerne and p-styryldiphenylphosphine (5:1), con-
taining 2% divinylbenzene (4) as cross-linking agent was treated with
excess bromoacetone to give polymeric acetonyltriphenylphosphonium
bromide (PATPB) in quantitative yield. Each gram of the polymeric
phosphonium salt contained ca. 1.88 mmol of phosphine estimated
from the elemental analysis.[14] We employed this home-made resin
in the present study. Polymer-supported triphenylphosphine (2.6–
3.2 mmol/g on polystyrene, 2% crosslinked, 200–400 mesh) is also
commercially available.[15] It can also be employed to prepare the cor-
responding polymeric acetonyltriphenylphosphonium bromide (PATPB).
We tried to find out optimal reaction condition for the acetal forma-
tion catalyzed by PATPB. To a solution of 3-phenylpropanal (1)
(321.6 mg, 2.40 mmol) in 2.4 mL of methanol was added PATPB
(127 mg, it is estimated to contain 0.24 mol equiv. of the acetonyltri-
phenylphosphonium bromide moiety) and the heterogeneous mixture

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2834
Hon et al.
Table 2. The reaction of aldehyde with alcohol or thiol in the presence of
PATPB catalysts at room temperature.
Acetal
or
PATPB
Entry R1CHO R1 ¼ (mol equiv.)
(mol Time
Yieldb
equiv.) (h) thiacetal (%)
Alcohol
MeOH
MeOH
a
1
2
PhCH2CH2À
PhCH2CH2À
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
PhCH2CH2À
Cyclohexyl 2
1
1
1
1/10
1/30
1/50
1/50
1/20
1/50
1/50
1/50
1/50
1/40
1/40
1/40
1/10
–
–
–
–
–
0.25
1.6
1a
1a
1a
2a
1b
1c
2c
1d
2d
1e
2e
1f
91
90
90
87
82
84
73
85
78
70
62
50
67
a
a
a
a
3
MeOH
MeOH
i-PrOH
10
4
24
48
48
48
24
26
24
24
24
24
5
1
1
6
HO(CH2)2OH
HO(CH2)2OH
HO(CH2)3OH
HO(CH2)3OH
EtSH
5
7
5
5
5
3
3
3
3
8
1
1
1
9
10
11
12
13
EtSH
HS(CH2)2SH
HS(CH2)3SH
2f
aAlcohol was used as solvent.
bIsolated yields.
was stirred at RT for 15 min to give the dimethylacetal 1a in 91% yield
(Entry 1, Table 2). When the mole ratio of aldehyde to phosphonium
bromide moiety on PATPB was changed to 1:30, the reaction took 1.6 h
to give the acetal 1a in 90% yield (Entry 2). When their mole ratio was
changed to 1:50, the reaction was complete only after 10 h to give the
acetal 1a in 90% yield (Entry 3). Thus, it is inferred that the mole ratio of
aldehyde to phosphonium bromide moiety on PATPB affects the reaction
rate significantly, but not on chemical yields. In order to minimize the use
of PATPB, we choose the reaction condition of Entry 3 for the further
study. In a typical procedure, PATPB (25 mg, 0.05 mol equiv. of the
catalytic moiety) was added to a solution of 3-phenylpropanal (1)
(321.6 mg, 2.40 mmol) in 2.4 mL of methanol and the reaction mixture
was stirred at RT. The reaction was complete in 10 h. The reaction
mixture was diluted with ethyl acetate (5 mL) followed by filtration
through a sintered glass funnel. The filtrate was concentrated to give a
practically pure product. In order to get analytically pure product, the
crude product was chromatographed on silica gel to give the desired
product 1a (388.8 mg, 2.16 mmol) in 90% yield (Entry 3, Table 2).
Using the above procedure, 3-phenylpropanal (1) was reacted with
isopropanol, ethylene glycol, and 1,3-propanediol, respectively, to give

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Acetonyltriphenylphosphonium Bromide
2835
the corresponding acetals in good yields at room temperature within 48 h
(Entries 5, 6, 8, Table 2). Cyclohexanecarboxaldehyde (2) reacts with
methanol, ethylene glycol, and 1,3-propanediol, respectively, to give the
corresponding acetals in good yields (Entries 4, 7, 9, Table 2). All these
reactions were found to be complete within 48 h at RT. When the mole
ratio of aldehyde to phosphonium bromide moiety on PATPB was
changed to 1:40, both aldehydes 1 and 2 reacted with ethanethiol or
1,3-propanedithiol to give the corresponding dithioacetals 1e, 2e, 1f,
and 2f, respectively, in good yields (Entries 10, 11, 12, and 13).
The important feature of this polymer-supported reagent is that the
catalyst can be recovered by simple filtration during the work-up. We are
able to recover most of the PATPB. The recovered PATPB was washed
with benzene followed by drying in vacuo before reusing it. We have
tested the reactivity of the recovered PATPB and found that it can be
reused at least four times to protect 3-phenylpropanal as dimethyl acetal
in excellent yields. However, we did observe a slight decay of its catalytic
activity each time. It has been reported that a-bromo ketones undergo
debromination with polymer-supported triphenylphosphine in refluxing
methanol.[16] Presumably, the corresponding phosphonium bromide
might react with methanol under refluxing conditions to give the cor-
responding debrominated ketone. Our protection reactions were carried
out in the presence of alcohols at room temperature. This possible side
reaction might occur only in small portion. Therefore, the possible reason
of the decrease in reactivity of the PATPB after several times of reuse
might be due to the decomposition of the polymer-supported ATPB
moiety by the alcohols.
CONCLUSIONS
In summary, ATPB is a useful and economic catalyst to protect
aldehydes with methanol, ethylene glycol or1,3-porpanediol as their
corresponding acetals in excellent yields in a short reaction time. It is
also an effective catalyst to protect aldehydes with ethanethiol, or
1,3-propanedithiol as their corresponding dithioacetals in good yields
in short time. ATPB is also an effective catalyst for the protection of
cyclohexanone with 1,3-propandiol or 2,2-dimethylpropanediol as their
ketals in good yields. However, it is not a good catalyst for the protection
of acetophenone, a-tetralone, and 4-phenyl-2-butanone as their ketals. In
comparison, PATPB, its polymeric analogue, showed a good reactivity
forthe protection of aldehydes as theiracetals orthioacetals although the

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2836
Hon et al.
reaction time takes longer. However, it has the advantage in terms of the
easy work-up and isolation of the product. Furthermore, PATPB can be
recycled and reused several times, thereby making it a convenient catalyst
forthe protection of aldehydes as acetals orthioacetals.
EXPERIMENTAL
All reactions were carried out under nitrogen. Unless otherwise
noted, materials were obtained from commercial suppliers and used with-
1
out further purification. The H and 13C NMR spectra were recorded on
a Bruker Avance DPX400 spectrometer, and chemical shifts were given in
ppm downfield from tetramethylsilane (TMS). Infrared spectra were taken
with a JASCO FT/IR 460 plus spectrophotometer and only noteworthy
absorptions were listed. Mass spectra were measured on a VG Trio-
2000GC/MS spectrometer by electronic impact at 70 eV (unless otherwise
indicated). High Resolution Mass Spectroscopy (HRMS) was measured
on a Finnigan/Thermo Quest MAT 95XL (National Chung Hsing
University) or VG-11-250J Mass Spectrometer (National Chia-Tung
University). The acetonyltriphenyl-phosphonium bromide (ATPB) was
prepared by the reaction of bromoacetone with triphenylphosphine
according to the literature procedure.[11–13] The poly-p-styryldiphenyl-
acetonylphosphonium bromide (PATPB) was prepared by the reaction
of bromoacetone with the copolymer of p-styryldiphenlyphosphine,
styrene, and p-divinylbenzene according to our previous report.[14]
General procedure of the protection of aldehyde with alcohol in the
presence of ATPB. To a solution of 3-phenylpropanal (1) (287 mg,
2.14 mmol) in 2 mL of methanol was added ATPB (85 mg, 0.21 mmol)
and the solution was stirred at RT. The reaction was complete in 20 min.
The solution was concentrated and the residue was chromatographed
on silica gel to give the desired product 1a (358.8 mg, 1.99 mmol) in
93% yield.
General procedure of the protection of aldehyde with diol in the pre-
sence of ATPB. To a solution of 3-phenylpropanal (1) (314 mg,
2.34 mmol) and ethylene glycol (160 mg, 2.58 mmol) in 2 mL of CH2Cl2
was added ATPB (92 mg, 0.23 mmol) and the solution was stirred at RT.
The reaction was complete in 45 min, after which the solution was
concentrated and chromatographed on silica gel to give the desired
product 1c (383.4 mg, 2.16 mmol) in 92% yield.
General procedure of the protection of aldehyde with thiol in the
presence of ATPB. To a solution of 3-phenylpropanal (1) (278 mg,
2.07 mmol) and ethanethiol (270 mg, 4.36 mmol) in 2 mL of CH2Cl2

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Acetonyltriphenylphosphonium Bromide
2837
was added ATPB (83 mg, 0.21 mmol) and the solution was stirred at RT.
The reaction was complete in 30 min. Then the solution was concentrated
in well-ventilated fuming hood and chromatographed on silica gel to give
the desired product 1e (447.3 mg, 1.86 mmol) in 90% yield.
General procedure of the protection of aldehydes with alcohol in the
presence of PATPB. To a solution of 3-phenylpropanal (1) (321.6 mg,
2.40 mmol) in 2.4 mL of methanol was added PATPB (25 mg, it is
estimated to be 0.05 mol equiv. of the catalytic moiety) and the hetero-
geneous mixture was stirred at RT. The reaction was complete in 10 h.
Then the reaction mixture was diluted with ethyl acetate and filtered
through a sintered glass funnel. The solution was concentrated and the
residue chromatographed on silica gel to give the desired product 1a
(388.8 mg, 2.16 mmol) in 93% yield.
General procedure of the protection of aldehydes with diol in the
presence of PATPB. To a mixture of 3-phenylpropanal (1) (321.6 mg,
2.40 mmol) and ethylene glycol (744.84 mg, 12.0 mmol) was added
PATPB (25 mg, 0.05 mol equiv. of the catalytic moiety) and the hetero-
geneous mixture was stirred at RT. The reaction was complete in 48 h,
afterwhich the solution was diluted with ethyl acetate and filteerd
through a sintered glass funnel. The filtrate was concentrated and
chromatographed on silica gel to give the desired product 1c (358.8 mg,
2.02 mmol) in 84% yield.
General procedure of the protection of aldehydes with thiol in the
presence of PATPB. To a mixture of 3-phenylpropanal (1) (321.6 mg,
2.40 mmol) and ethanethiol (313.1 mg, 5.04 mmol) in 2.4 mL of CH2Cl2
was added PATPB (25 mg, 0.05 mol equiv. of the catalytic moiety). The
heterogeneous mixture was stirred at RT and the reaction was complete
in 48 h. The reaction mixture was diluted with ethyl acetate and filtered
through a sintered glass funnel. The filtrate was concentrated and the
residue was chromatographed on silica gel to give the desired product
1e (518.6 mg, 2.16 mmol) in 90% yield.
General procedure of the protection of aldehyde with dithiol in the
presence of PATPB. To a mixture of 3-phenylpropanal (1) (321.6 mg,
2.40 mmol) and 1,3-propanedithiol (389.6 mg, 3.60 mmol) in 2.4 mL of
CH2Cl2 was added PATPB (25 mg, 0.05 mol equiv. of the catalytic
moiety). The heterogeneous mixture was stirred at RT and the reaction
was complete in 24 h. The reaction mixture was diluted with ethyl acetate
and filtered through a sintered glass funnel. The filtrate was concentrated
and chromatographed on silica gel to give the desired product 1f
(268.8 mg, 2.16 mmol) in 50% yield.
3-Phenylpropionaldehyde dimethyl acetal (1a).[17] 1H NMR (CDCl3,
400 MHz) ꢀ 1.90–1.95 (m, 2H, PhCH2CH2À), 2.67 (dd, J ¼ 8.2 and

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2838
Hon et al.
6.1 Hz, 2H, PhCH2À), 3.33 (s, 6H, –OCH3), 4.37 (t, J ¼ 5.7 Hz, 1H,
–CH(OCH3)2), 7.18–7.28 (m, 5H, Ar-H). 13C NMR (CDCl3, 100 MHz)
ꢀ 30.8 (PhCH2CH2À), 34.1 (PhCH2À), 52.7 (–OCH3), 103.8 (–CH(OCH3)2),
125.8, 128.4, 141.6 (4ꢀ). IR (KBr) 2958, 1604, 1493, 1457, 1383 cmÀ1
.
MS m/z (relative intensity): 180 (Mþ, 4), 148 (89), 91 (100), 75 (96).
HRMS calcd. forC 11H16O2: 180.1151. Found: 180.1147.
3-Phenylpropionaldehyde diisopropyl acetal (1b).[18] 1H NMR (CDCl3,
400 MHz) ꢀ 1.13 (d, J ¼ 6.1 Hz, 6H, –OCH(CH3)2), 1.20 (d, J ¼ 6.2 Hz,
6H, –OCH(CH3)2), 1.90–1.93 (m, 2H, PhCH2CH2À), 2.69 (t, J ¼ 8.2 Hz,
2H, PhCH2À), 3.83–3.86 (m, 2H, –OCH(CH3)2), 4.55 (1H,
–CH(OC3H7)2), 7.18–7.26 (m, 5H, Ar-H). 13C NMR (CDCl3, 100 MHz)
ꢀ 22.5, 23.4, 31.0 (PhCH2CH2À), 36.9 (PhCH2À), 67.6 (–OCH(CH3)2), 99.6
(–CH(OC3H7)2), 125.6, 128.2, 128.3, 142.0 (4ꢀ). IR (KBr) 2967, 1461,
1374 cmÀ1. MS m/z (relative intensity): 235 (MþÀ1, 0.2), 117 (18), 148
(31), 91 (59), 75 (100). HRMS calcd. forC 15H24O2: 236.1777. Found:
236.1770.
2-(2-Phenylethyl)-1,3-dioxolane (1c).[19] 1H NMR (CDCl3, 400 MHz)
ꢀ 2.03–2.08 (m, 2H, PhCH2CH2À), 2.80–2.84 (m, 2H, PhCH2À), 3.88–3.92
(m, 2H, –OCH2CH2O–), 4.02–4.05 (m, 2H, –OCH2CH2O–), 4.96
(t, J ¼ 4.7 Hz, 1H, –CH(OCH2)2), 7.24–7.36 (m, 5H, Ar-H). 13C NMR
(CDCl3, 100 MHz)
ꢀ 30.1 (PhCH2CH2À), 35.4 (PhCH2À), 64.8
(–OCH2À), 103.7 (–CH(OCH2)2), 125.8, 128.3, 141.5 (4ꢀ). IR (KBr)
2949, 2875, 1599, 1493, 1457 cmÀ1. MS m/z (relative intensity): 178
(49), 116 (81), 91 (95), 100 (100). HRMS calcd. forC 11H14O2:
178.0994. Found: 178.0994.
2-(2-Phenylethyl)-1,3-dioxane (1d).[20] 1H NMR (CDCl3, 400 MHz) ꢀ
1.26–1.31 (m, 1H, –CH2CH2CH2À), 1.88–1.93 (m, 2H, PhCH2CH2À),
2.04–2.08 (m, 1H, –CH2CH2CH2À), 2.71 (t, J ¼ 8.3 Hz, 2H, PhCH2À),
3.67–3.74 (m, 2H, –OCH2CH2À), 4.06–4.10 (m, 2H, –OCH2CH2À) 4.49
(t, J ¼ 5.2 Hz, 1H, –CH(OCH2)3), 7.14–7.27 (m, 5H, Ar-H). 13C NMR
(CDCl3, 100MHz) ꢀ 25.7 (–CH2CH2CH2À), 30.0 (PhCH2CH2À), 36.5
(PhCH2À), 66.7 (–OCH2À), 101.3 (–CH(OCH2)3), 125.7, 128.2, 128.3,
141.6 (4ꢀ). IR (KBr) 2949, 2857, 1604, 1498, 1457, 1383 cmÀ1. MS m/z
(relative intensity): 192 (Mþ, 55), 133 (69), 114 (76), 86 (100). HRMS
calcd. forC 12H16O2: 192.1151. Found: 192.1157.
3-Phenylpropanal diethyl thioacetal (1e).[21] 1H NMR (CDCl3,
400 MHz) ꢀ 1.22 (t, J ¼ 7.5 Hz, 1H, –SCH2CH3), 2.10 (q, J ¼ 7.8 Hz,
2H), 2.54–2.88 (m, 8H), 2.85 (t, J ¼ 7.9 Hz, 2H), 3.73 (t, J ¼ 7.1 Hz, 1H,
–CH(SEt)2, 7.16–7.26 (m, 5H, Ar-H). 13C NMR (CDCl3, 100 MHz) ꢀ
14.4 (–SCH2CH3), 23.9 (–SCH2CH3), 33.3 (PhCH2CH2À), 37.5 (PhCH2À),
50.4 (–CH(SEt)2, 125.8, 128.3, 128.4, 141.0 (4ꢀ). IR (KBr) 3022,
2921, 1595, 1489, 1452, 1378 cmÀ1. MS m/z (relative intensity): 240

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Acetonyltriphenylphosphonium Bromide
2839
(Mþ, 3), 178 (19), 117 (100), 91 (79). HRMS calcd. forC 13H20S2:
240.1008. Found: 240.1016.
2-(2-Phenylethyl)-1,3-dithiolane (1f).[22] 1H NMR (CDCl3, 400 MHz)
ꢀ 1.85–1.88 (m, 1H), 2.04–2.12 (m, 3H), 2.81–2.84 (m, 6H), 3.98
(t, J ¼ 7.0 Hz, 1H), 7.17–7.30 (m, 5H, Ar-H). 13C NMR (CDCl3;
100MHz) ꢀ 25.9, 30.1, 32.4, 36.8, 46.4, 125.9, 128.3, 128.4, 140.8 (4ꢀ).
IR (KBr) 3032, 2930, 1609, 1493, 1420 cmÀ1. MS m/z (relative intensity):
224 (Mþ, 1), 196 (74), 131 (33), 121 (100). HRMS calcd. forC 12H16S2:
224.0695. Found: 224.0701.
3-Phenylpropionaldehyde 3-propanethiol thioacetal (1f0). 1H NMR
(CDCl3, 400 MHz) ꢀ 1.38 (t, J ¼ 8.0 Hz, 2H), 1.85–1.88 (m, 4H),
2.10–2.12 (m, 2H), 2.60–2.87 (m, 10H), 3.69 (1H, –CH(SR)2), 7.19–7.29
(m, 5H, Ar-H). 13C NMR (CDCl3, 100 MHz) ꢀ 23.6, 28.4, 33.2, 33.4, 37.5,
51.2, 126.1, 128.5, 140.8 (4ꢀ). IR (KBr) 3022, 2921, 2543, 1604, 1493,
1442 cmÀ1. MS m/z (relative intensity): 332 (Mþ, 50), 225 (25), 117
(100). HRMS calcd. forC 15H24S4: 332.0763. Found: 332.0771.
Cyclohexanecarboxaldehyde dimethyl acetal (2a).[17] 1H NMR
(CDCl3, 400 MHz) ꢀ 0.97–1.23 (m, 5H), 1.58–1.79 (m, 6H), 3.33 (s, 6H,
-OCH3), 3.99 (d, J ¼ 7.2 Hz, 1H, –CH(OCH3)2). 13C NMR (CDCl3,
100 MHz) ꢀ 25.7, 26.4 28.0, 40.0, 53.5 (1ꢀ, –OCH3), 108.5 (3ꢀ,
–CH(OCH3)2). IR (KBr) 2912, 1452, 1378 cmÀ1. MS m/z (relative intensity):
158 (Mþ, 4), 154 (100), 136 (74), 117 (37).
Cyclohexanecarbaldehyde diisopropyl acetal (2b).[23] 1H NMR
(CDCl3, 400 MHz) ꢀ 0.93–1.05 (m, 2H), 1.06–1.30 (m, 14H), 1.40–1.52
(m, 1H), 1.58–1.86 (m, 6H), 3.78–3.89 (m, 2H, –OCH(CH3)2), 4.23
(d, J ¼ 6.1 Hz, 1H, –CH(OR)2). 13C NMR (CDCl3, 100 MHz) ꢀ 22.6
(1ꢀ), 23.4 (1ꢀ), 26.0 (2ꢀ), 26.5 (2ꢀ), 28.2 (2ꢀ), 42.2 (3ꢀ), 68.0
(3ꢀ, –CH(OCH3)2), 103.7 (3ꢀ, –CH(OR)2). IR (KBr) 2930, 1456,
1382 cmÀ1. MS m/z (relative intensity): 117 (MþÀ97, 4), 91 (50), 71
(43), 69 (44), 55 (100).
2-Cyclohexyl-1,3-dioxolane (2c).[24] 1H NMR (CDCl3, 400 MHz) ꢀ
1.07–1.25 (m, 5H), 1.53–1.80 (m, 6H), 3.81–3.94 (m, 4H,
–OCH2CH2O–), 4.59 (d, J ¼ 5.0 Hz, 1H, –CH(OCH2)2). 13C NMR
(CDCl3, 100 MHz) ꢀ 25.6, 26.3, 27.2, 41.6, 64.8 (2ꢀ, –OCH2À), 107.5
(3ꢀ, –CH(OCH2)2). IR (KBr) 2921, 1452, 1397, 1272 cmÀ1. MS m/z
(relative intensity): 156 (Mþ, 8), 155 (MþÀ1, 14), 73 (100). HRMS
calcd. for(M þÀH) C9H15O2: 155.1073. Found: 155.1073.
2-Cyclohexyl-1,3-dioxane (2d).[20] 1H NMR (CDCl3, 400 MHz)
ꢀ 1.00–1.33 (m, 6H), 1.48–1.49 (m, 1H), 1.63–1.80 (m, 5H), 2.03–2.06
(m, 1H), 3.70–3.76 (m, 2H, –OCH2CH2À), 4.07–4.11 (m, 2H,
–OCH2CH2À), 4.23 (d, J ¼ 5.3 Hz, 1H, –CH(OCH2)3). 13C NMR
(CDCl3, 100 MHz) ꢀ 25.7, 26.0, 26.4, 27.3, 42.5, 66.8 (–OCH2À), 105.3

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2840
Hon et al.
(–CH(OCH2)3). IR (KBr) 2921, 1452, 1378, 1240 cmÀ1. MS m/z (relative
intensity): 87 (MþÀ83, 100), 83 (24), 55 (57). HRMS calcd. forC 10H18O2:
170.1307. Found: 170.1307.
Cyclohexanecarbaldehyde diethyl thioacetal (2e).[21] 1H NMR
(CDCl3, 400 MHz) ꢀ 1.18–1.28 (m, 11H), 1.67–1.94 (m, 6H), 2.59–2.70
(m, 4H, –SCH2CH3), 3.65 (d, J ¼ 5.6 Hz, 1H, –CH(SEt)2). 13C NMR
(CDCl3, 100 MHz) ꢀ 14.6 (–SCH2CH3), 25.7, 26.3, 26.4, 30.7 (2ꢀ,
–SCH2CH3), 43.4, 58.7 (3ꢀ, –CH(SEt)2. IR (KBr) 2912, 1443, 1369,
1254 cmÀ1. MS m/z (relative intensity): 218 (Mþ, 28), 157 (84), 95
(100), 75 (75). HRMS calcd. forC 11H22S2: 218.1165. Found: 218.1165.
2-Cyclohexyl-1,3-dithioxane (2f ).[22] 1H NMR (CDCl3, 400 MHz) ꢀ
1.18–1.27 (m, 4H), 1.63–1.90 (m, 7H), 2.08–2.13 (m, 1H), 2.13–2.88 (m,
4H), 4.04 (d, J ¼ 5.4 Hz, 1H, –CH(SR)2). 13C NMR (CDCl3, 100 MHz) ꢀ
26.1, 26.2, 26.4, 30.4, 30.9, 43.1, 55.3. IR (KBr) 2921, 2847, 1452,
1268 cmÀ1. MS m/z (relative intensity): 202 (Mþ, 25), 119 (100), 107
(100), 95 (8.0). HRMS calcd. forC 10H18S2: 202.0851. Found: 202.0849.
Cyclohexanylcarbaldehyde 3-propanethiol thioacetal (2f 0). H NMR
1
(CDCl3, 400 MHz) ꢀ 1.27–1.44 (m, 6H), 1.78–1.96 (m, 9H), 2.64–2.82
(m, 10H), 3.64 (d, J ¼ 5.6 Hz, 1H, –CH(SR)2). 13C NMR (CDCl3,
100 MHz) ꢀ 23.5, 26.1, 26.2, 29.9, 30.7, 33.2, 43.1, 59.4. IR (KBr) 2921,
2838, 1447, 1347, 1263 cmÀ1. MS m/z (relative intensity): 309 (MþÀ1, 4),
203 (28), 107 (100), 95 (48). HRMS calcd. forC 13H26S4: 310.0920.
Found: 310.0925.
1,4-Dioxaspiro[4.5]decane (3a).[25] 1H NMR (CDCl3, 400 MHz) ꢀ
1.39–1.40 (brs, 2H), 1.57–1.60 (brs, 8H), 3.93 (brs, 4H,
–O(CH2)2O–). 13C NMR (CDCl3, 100 MHz) ꢀ 23.9 (2ꢀ), 25.2 (2ꢀ), 35.2
(2ꢀ), 64.1 (2ꢀ), 109.0 (4ꢀ). IR (KBr) 2936, 1447, 1366, 1282, 1162,
1104 cmÀ1
.
3,3-Dimethyl-1,5-dioxaspiro[5.5]undecane (3b).[26] 1H NMR (CDCl3,
400 MHz) ꢀ 0.96 (brs, 6H), 1.30–1.60 (m, 6H), 1.70–1.85 (m, 4H), 3.49
(brs, 4H). 13C NMR (CDCl3, 100 MHz) ꢀ 22.50 (1ꢀ), 22.71 (2ꢀ), 25.70
(2ꢀ), 30.10 (4ꢀ), 32.50 (2ꢀ), 69.73 (2ꢀ), 97.62 (4ꢀ). IR (KBr) 2937, 2858,
1473, 1446, 1393, 1268 cmÀ1. MS m/z (relative intensity): 309 (MþÀ1, 4),
203 (28), 107 (100), 95 (48). HRMS calcd. forC 11H20O2: 184.1464.
Found: 184.1466.
ACKNOWLEDGMENT
We are grateful to the National Science Council, National Chung
Cheng University and Academia Sinica, Republic of China for financial
support.

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Acetonyltriphenylphosphonium Bromide
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2841
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Received in Japan November20, 2002

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