2
8
204 Bull. Chem. Soc. Jpn., 75, No. 10 (2002)
TABCO as a Catalyst for Chemoselective Protection
.29 (m, 2H).
(Table 9) was added at 50 °C. The progress of the reaction was
monitored by TLC or GC. After completion, the reaction was
quenched with cold water (10 mL), and the mixture was extracted
General Procedure for the Synthesis of Cyclic Diacetals by
Condensation of 2,2-Bis(hydroxymethyl)-1,3-propandiol with
Carbonyl Compounds Catalyzed by TABCO: A mixture of
carbonyl compounds (2.0 mmol), 2,2-bis(hydroxymethyl)-1,3-
propandiol (pentaerythritol) (1.2 mmol), and TABCO (Table 7) as
a catalyst in dry ethanol (10 mL) was stirred at refluxing tempera-
ture using a Dean–Stark apparatus for water removal. The
progress of the reaction was monitored by TLC and GC. After
completion, the mixture was cooled and then NaOH (5%, 25 mL)
was added. The mixture was extracted with CH
The organic layer was washed with water (2 × 20 mL) and dried
over anhydrous Na SO Evaporation of the solvent under re-
duced pressure provided a crude product. The crude product was
purified by silica-gel column chromatography (petroleum ether
with CHCl
washed with saturated NaHCO
then dried over Na SO . Evaporation of the solvent under reduced
3
(3 × 30 mL). The organic layer was separated and
3
(2 × 25mL) and water 15 mL and
2
4
pressure gave the most pure acylals (1,1-diacetate). Further purifi-
cation by column chromatography on silica gel using petroleum
ether 60–80 °C/EtOAc as eluent afforded the desired product(s) in
good-to-excellent yield(s) (Table 9). All of the products were
known compounds and were identified by comparisons of their
2 2
Cl (3 × 30 mL).
1
13
spectral data (IR, H NMR, C NMR, and MS) with those report-
3
3–34
2
4
.
ed in the literature.
the following aldehydes:
Selected spectral data for some acylals of
3
3–34
1
Benzaldehyde: H NMR (CDCl
3
, 250 MHz), δ 7.67 (s, 1H),
7.40 (s, 5H), 2.12 (s, 6H); C NMR (CDCl , 63 MHz), δ 168.1,
135.4, 129.3, 128.2, 126.2, 89.5, 20.1. IR (nujol) 1750, 1380,
13
6
0–80 °C/CHCl
3
, 8/2) to afford pure crystals of their correspond-
3
ing diacetals in good-to-excellent yields. The crude product could
also be purified by recrystallization in alcohols such as ethanol,
butanol, and isopropyl alcohol to give pure crystalline diacetals
−
1
1245, 1210, 1065, 1015, 960, 758, 695 cm
4-Nitrobenzaldehyde H NMR (CDCl
(d, 2H), 7.47 (d, 2H), 7.45 (s, 1H), 2.10 (s, 6H). IR (nujol)
1760,1540, 1460, 1236, 1095, 1060 cm .
4-Chlorobenzaldehyde: H NMR (CDCl
(s, 1H), 7.31 (s, 4H), 2.12 (s, 6H). IR (nujol) 1755, 1605, 1495,
1375, 1215 cm
4-Methoxybenzaldehyde: H NMR (CDCl
7.42 (s, 1H), 7.35 (d, 2H), 6.75 (d, 2H), 3.81 (s, 3H), 2.13 (s, 6H).
IR (nujol) 1763, 1614, 1519, 1372, 1241, 1204 cm .
Butyraldehyde: H NMR (CDCl
1H), 2.40–2.20 (m, 2H), 2.01 (s, 6H), 1.90–1.30 (m, 2H), 1.02 (t,
.
1
3
, 250 MHz), δ 8.05
(
Table 7). All of the products were known compounds, and were
1
13
−1
identified by comparisons of their spectral data (IR, H NMR,
NMR, and MS) with those reported in the literature. Selected
spectral data for some cyclic diacetals with the following alde-
C
3
0
1
3
, 250 MHz), δ 7.50
3
0
−1
hydes:
Benzaldehyde: H NMR (CDCl
m, 10H), 5.01 (d, 2H), 4.34 (s, 2H), 4.01–3.52 (m, 6H). IR 2960,
.
1
1
3
, 250 MHz), δ 7.70–7.42
3
, 250 MHz), δ
(
−
1
−1
2
925, 1600, 1175, 745, 965 cm
.
1
1
4
-Methylbenzaldehyde: H NMR (CDCl
3
, 250 MHz), δ
3
, 250 MHz), δ 6.51 (m,
7
3
1
.30–7.12 (m, 8H), 5.42 (s, 2H), 4.85 (d, 2H), 3.81–3.72 (m, 4H),
−
1
.60 (d, 2H), 2.34 (s, 6H). IR 2910, 2862, 1600, 1460, 1390,
3H). IR (nujol) 2960, 1765,1374, 1244, 1208, 1010 cm .
050, 805 cm−
1
.
Cinnamaldehyde: H NMR (CDCl
(m, 6H), 6.87 (d, 1H), 5.93 (dd, 1H), 2.10 (s, 6H). C NMR
(CDCl , 63 MHz), δ 168.2, 136.4, 135.3,128.8, 127.6, 127.0,
121.8, 89.7, 20.8. IR (nujol) 1755, 1660, 1490, 1470, 1245, 1195,
1
, 250 MHz), δ 7.60–7.10
3
1
13
4
-Chlorobenzaldehyde: H NMR (CDCl
3
, 250 MHz), δ
7
.61–7.02 (dd, 8H), 4.55 (d, 2H), 4.33 (s, 2H), 3.61–3.23 (m, 6H).
3
−
1
IR(neat) 2960, 2930, 1600, 1500, 1090, 820 cm
.
1
−1
Furfural: H NMR (CDCl
3
, 250 MHz), δ 7.61–7.42 (m, 6H),
1120, 1060, 1005,940, 748, 690 cm .
1
4
2
.90 (d, 2H), 4.24 (s, 2H), 3.61–3.22 (m, 6H). IR(neat) 2960,
4-Methylbenzaldehyde: H NMR (CDCl
3
, 250 MHz), δ 7.31
(q, 4H), 2.35 (s, 3H), 2.10 (s, 6H). C NMR (CDCl , 63 MHz), δ
168.6, 139.6, 132.8, 129.2, 126.6, 89.8, 21.1, 20.7. IR (nujol)
940, 2850, 1090, 740 cm−
1
.
13
3
Direct Conversion of Epoxides to 1,3-Dioxolanes Catalyzed
1765, 1750, 1230, 1205, 1070, 1005, 960, 930, 815 cm−
.
1
with TABCO in Dry Acetone under Reflux Conditions: To a
solution of epoxide (1.0 mmol) in dry acetone (5 mL), appropri-
ate amounts TABCO (Table 8) were added, and the resulting solu-
tion was stirred under the reflux condition. The progress of the re-
action was monitored by TLC or GC. After completion (Table 8),
the reaction was quenched with a cold aqueous solution of NaOH
The authors are thankful to the Shiraz University Research
Council for the partial support of this work.
References
(
5%, 20 mL) and the mixture was extracted with CH
mL). The organic extracts were washed with water (2 × 20 mL),
and dried over anhydrous Na SO . Evaporation of the solvent un-
2 2
Cl (3 × 30
1
a) T. W. Greene and P. G. M. Wuts, “Protective Groups in
2
4
Organic Synthesis,” 2nd ed, John Wiley, NewYork (1991); b) A. J.
Pearson and W. J. Roush, “Handbook of Reagents for Organic
Synthesis Activating Agents and Protecting Groups,” 1st ed, John
Wiley, New York (1999).
P. J. Kocienski, “Protective Groups,” ed by R. Enders, R.
Noyori, and B. M. Trost, Thieme, Stuttgart (1994).
D. Seebach, R. Imwinkelried, and T. Weber, “Modern Syn-
der reduced pressure gave almost pure 1,3-dioxolanes. Further
purification was achieved by vacuum distillation to give pure
product(s) in-good-to excellent yield(s) (Table 8). All of the prod-
ucts were known compounds, and were identified by comparisons
of their spectral data (IR, H NMR, C NMR, and MS) with those
reported in the literature.
2
1
13
3
1–32
Selected spectral data for:
3
3
1–32
2
,2-Dimethyl-4-phenyl-1,3-dioxolane:
(Table 8, Entry
, 250 MHz), δ 7.10 (s, 5H), 4.85 (dd, 1H),
thetic Methods,” ed by R. Scheffold, Springer-Verlag, Berlin
(1986), Vol. 4, pp. 125-256.
1
1
4
3
7
): H NMR (CDCl
3
.12 (dd, 1H), 3.45 (dd, 1H), 1.43 (s, 3H), 1.38 (s, 3H). IR (neat)
4
a) E. G. Howard and R. V. Lindsey, J. Am. Chem. Soc., 82,
040, 2990, 3880, 1500, 1450, 1370, 1220, 1160, 1070, 950, 860,
158 (1960); b) R. A. Daignault and E. L. Elier, Org. Synth., Coll.
Vol. V, 303 (1973); c) N. H. Anderson and H. S. Uh, Synth. Com-
mun., 125, 3 (1973); d) F. T. Brown, R. H. Lenhard, and S.
Bernstein, J. Am. Chem. Soc., 86, 2183 (1964); e) F. T. Bond, J. E.
Stemke, and D. W. Powell, Synth. Commun., 5, 427 (1975); f) R.
Sterzycki, Synthesis, 1979, 724.
90, 700 cm−
1
.
General Procedure for the Preparation of Acylals (1,1-Di-
acetate) from Aldehydes Catalyzed with TABCO in the Pres-
ence of Acetic Anhydride: To a magnetically stirred solution of
2
aldehydes (1.0 mmol) and freshly distilled AC O (2mL), TABCO