Y.-G. Wang et al. / Tetrahedron Letters 45 (2004) 2973–2976
Table 6. Deprotection of tetrahydropyranyl ethers of phenols and
2975
References and notes
2 3 2
alcohols catalyzed by PdCl (CH CN)
1
. (a) Greene, T. W.; Wuts, P. G. M. Protective Groups in
Organic Synthesis. 3rd ed.; John Wiley and Sons: New
York, 1999, pp 49–54; (b) Kocienski, P. J. In Protecting
Groups; Enders, D., Noyori, R., Trost, B. M., Eds.; Georg
Thieme: Stuttgart, 1994; pp 83–85.
0
.1 equiv. PdCl
2 3 2
(CH CN)
ROH
RO
O
3
CH CN , reflux
Entry
R
Reaction
time (h)
Yield
a
(%)
2
. (a) Creenhalgh, C. W.; Henbest, H. B.; Jones, E. R. H.
J. Chem. Soc. 1951, 1190–1193; (b) Ott, A. C.; Murray, M.
F.; Pederson, R. L. J. Am. Chem. Soc. 1952, 74, 1239–
1241; (c) Jones, R. G.; Mann, M. J. J. Am. Chem. Soc.
1953, 75, 4048–4052; (d) Miyashita, M.; Yoshikoshi, A.;
Grieco, P. A. J. Org. Chem. 1977, 42, 3772–3774; (e) Torii,
S.; Inokuchi, T.; Kondo, K.; Ito, H. Bull. Chem. Soc. Jpn.
1985, 58, 1347–1348; (f) Bolitt, V.; Mioskowski, C.; Shin,
D. S.; Falck, J. R. Tetrahdron Lett. 1988, 29, 4583–4586;
(g) Yadav, J. S.; Srinivas, D.; Reddy, G. S. Synth.
Commun. 1998, 28, 1399–1404; (h) Branco, L. C.; Afonso,
C. A. M. Tetrahedron 2001, 57, 4405–4410; (i) Hon, Y.-S.;
Lee, C.-F.; Chen, R.-J.; Szu, P.-H. Tetrahedron Lett. 2001,
57, 5991–6001; (j) Naik, S.; Gopinath, R.; Patel, B. K.
Tetrahedron Lett. 2001, 42, 7679–7681; (k) Ravindranath,
N.; Ramesh, C.; Das, B. Synlett 2001, 1777–1778; (l)
Romanelli, G. P.; Baronetti, G.; Thomas, H. J.; Autino,
J. C. Tetrahedron Lett. 2002, 43, 7589–7591.
1
2
3
4
5
6
7
8
9
CH
3
(CH
CH
4-NO
CH
2
)
6
CH
2
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
11.5
11
82
75
C
6
H
5
2
2
C
6
H
4
CH
2
11
87
C
6
H
5
2
CH
2
15
93
c-C
t-C
4-ClC
4-CH
TsO(CH
TBSO(CH
TBDPSO(CH
6
H
11
18
48
37
Trace
95
4
H
9
6
H
4
6.0
6.0
14
3
OC
6
H
4
91
2
)
6
89
b
10
11
12
13
14
15
2
)
4
12
16
Trace
72
85
2
)
4
CbzO(CH
AllylO(CH
BnO(CH
BzO(CH
2
)
4
13
11
2
)
4
59
2
)
4
12
80
c
2
)
4
8.0
88
a
b
c
Isolated yield (average of two runs).
TBS was deprotected under the reaction conditions.
The product is 4-benzoyl-1-butanol (36).
3
4
. (a) Alper, H.; Dinkes, L. Synthesis 1972, 81; (b) Nam-
boodiri, V. V.; Varma, R. S. Tetrahedron Lett. 2002, 43,
1
143–1146; (c) Karimi, B.; Maleki, J. Tetrahedron Lett.
002, 43, 5353–5355.
. Brown, D. S.; Ley, S. V.; Vile, S.; Thompson, M.
2
Tetrahedron 1991, 47, 1329–1342.
1
5
5. (a) Tanemura, K.; Horaguchi, T.; Suzuki, T. Bull. Chem.
Soc. Jpn. 1992, 65, 304–305; (b) Deka, N.; Sarma, J. C.
J. Org. Chem. 2001, 66, 1947–1948.
Recently, Spencer and co-workers demonstrated that
protons, rather than metal ions, were the active catalysts
2 3 2
in PdX (CH CN) mediated hetero-Michael addition
reactions in the presence of small amount of water.
Based on these facts, it is possible that protons from the
6
. (a) Iqbal, J.; Srivastava, R. R.; Gupta, K. B.; Khan, M. A.
Synth. Commun. 1989, 19, 901–906; (b) Bhuma, V.;
Kantam, M. L. Synth. Commun. 1992, 22, 2941–2944; (c)
Maity, G.; Roy, S. C. Synth. Commun. 1993, 23, 1667–
1671; (d) Kantam, M. L.; Santhi, P. L. Synth. Commun.
1993, 23, 2225–2228; (e) Ma, S.; Venanzi, L. M. Tetrahe-
dron Lett. 1993, 34, 5269–5272; (f) Bhalerao, U. T.; Davis,
K. J.; Rao, B. V. Synth. Commun. 1996, 26, 3081–3085; (g)
Molnar, A.; Beregszaszi, T. Tetrahedron Lett. 1996, 37,
2 3 2 3
hydrolyis of PdCl (CH CN) in CH CN (with a small
amount of water) under reflux act as the active catalysts
in our deprotection reaction. The researches on the
mechanism of this catalytic reaction are in progress.
In conclusion, we have developed an efficient and facile
method for the formation and cleavage of THP ethers.
Primary alcohols could be chemoselectively tetrahy-
dropyranylated in the presence of phenols, secondary,
8
597–8600; (h) Habibi, M. H.; Tangesaninejad, S.;
Mohammadpoor-Baltork, I.; Mirkhani, V.; Yadollahi, B.
Tetrahedron Lett. 2001, 57, 2851–2853; (i) Pachamuthu,
K.; Vankar, Y. D. J. Org. Chem. 2001, 66, 7511–7513; (j)
Mineno, T. Tetrahedron Lett. 2002, 43, 7975–7978.
and tertiary alcohols by using PdCl (CH CN) in
2
3
2
anhydrous THF at room temperature. Meanwhile,
chemoselective deprotection of THP ethers of phenols
7
. (a) Bongini, A.; Cardillo, G.; Orena, M.; Sandri, S.
Synthesis 1979, 618–620; (b) Menger, F. M.; Chu, C. H.
J. Org. Chem. 1981, 46, 5044–5045; (c) Olah, G. A.;
Husain, A.; Singh, B. P. Synthesis 1983, 892–895; (d)
Hoyer, S.; Laszlo, P.; Orlovic, M.; Polla, E. Synthesis
and
PdCl
primary alcohols
was
achieved
using
(CH CN) in wet MeCN at reflux temperature.
2
3
2
The THP-protected secondary and tertiary alcohols as
well as Ts-, TBDPS-, Bn-, Allyl-, Bz-, and Cbz-protected
alcohols are stable under these conditions.
1
986, 655–657; (e) Johnston, R. D.; Marston, C. R.;
Krieger, P. E.; Goe, G. L. Synthesis 1988, 393–394; (f)
Patney, H. K. Synth. Commun. 1991, 21, 2329–2333; (g)
Chavez, F.; Godinez, R. Synth. Commun. 1992, 22, 159–
1
64; (h) Campelo, J. M.; Garcia, A.; Lafont, F.; Luna, D.;
Marinas, J. M. Synth. Commun. 1992, 22, 2335–2342; (i)
Kumar, P.; Dinesh, C. U.; Reddy, R. S.; Pandey, B.
Synthesis 1993, 1069–1070; (j) Campelo, J. M. Synth.
Commun. 1994, 24, 1345–1350; (k) Bandgar, B. P.; Jagtap,
S. R.; Aghade, B. B.; Wadgaonkar, P. P. Synth. Commun.
Acknowledgements
1
995, 25, 2211–2215; (l) Upadhya, T. T.; Daniel, T.;
This work was financially supported by the National
Natural Science Foundation of China (No 20272051) as
well as the Teaching and Research Award Program for
Outstanding Young Teachers in Higher Education
Institutions of MOE, P.R.C.
Sudalai, A.; Ravindranathan, T.; Sabu, K. R. Synth.
Commun. 1996, 26, 4539–4544.
8
. (a) Bauduin, G.; Bondon, D.; Pietrasanta, Y.; Pucci, B.
Tetrahedron 1978, 34, 3269–3274; (b) Corey, E. J.; Niwa,
H.; Knolle, J. J. Am. Chem. Soc. 1978, 100, 1942–1943; (c)