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Z. Han et al.
LETTER
Cl
TiCl4
Et3N
+
Cl
n-C10H21
OH
n-C10H21
n-C10H21
7
8
9
Scheme 3
Table Oxidation of Propargylic Alcohols with TiCl4/Et3N System
References and Notes
O
(1) a) Hudlicky, M. Oxidations in Organic Chemistry, ACS
Monograph Series: American Chemical Society: Washington
DC 1990. b) Nishimura, T.; Onoue, T.; Ohe, K.; Uemura, S. J.
Org. Chem. 1999, 64, 6750.
OH
TiCl4/Et3N
R
R
CH2Cl2
0 °C1h
H
1
2
(2) The TiCl4/R3N system has been extensively used in the
preparation of titanium enolates for aldol reactions. a) Evans,
D. A.; Clark, J. S.; Metternich, R.; Novack, V. J.; Sheppard,
G. S. J. Am. Chem. Soc. 1990, 112, 866. b) Evans, D. A.; Urpi,
F.; Somers, T. C.; Clark, J. S.; Bilodeau, M. T. J. Am. Chem.
Soc. 1990, 112, 8215. c) Evans, D. A.; Rieger, D. L.; Bilodeau,
M. t.; Urpi, F. J. Am. Chem. Soc. 1991, 113,1047. d) Harrison,
C. R. Tetrahedron Lett. 1987, 28, 4135. e) Annunziata, R.;
Cinquini, M.; Cozzi, f.; Cozzi, P. G.; Consolandi, E.
Tetrahedron 1991, 47, 7897. f) Xiang, Y.; Olivier, E.; Ouimet,
N. Tetrahedron Lett. 1992, 33, 457. g) Yan, T.-H.; Lee, H.-C.;
Tan, C.-W. Tetrahedron Lett. 1993, 34, 3559. h) Mahrwald,
R. Chem. Ber. 1995, 128, 919. h) Crimmins, M. T.; King, B.
W.; Tabet, E. A. J. Am. Chem. Soc. 1997, 119, 7883.
i) Yoshida, Y.; Hayashi, R.; Sumihara, H.; Tanabe, Y.
Tetrahedron Lett. 1997, 8727.
(3) The TiCl4/R3N reagent system has also been reported to be
effective for the oxidative coupling. a) Phenylacetic acid
esters to the corresponding 2,3-diphenylsuccinic acid
derivatives: Matsumura, Y; Nishimura, M.; Hiu, H.;
Watanabe, M.; Kise, N. J. Org. Chem. 1996, 61, 2809.
b) Terminal acetylenes into symmetrical 1,3-diynes. Bharathi,
P.; Periasamy, M. Organometallics 2000, 19, 5511.
(4) The formation of an iminium ion (Et2N+ = CHCH3Cl−) has
been reported. Bharathi, P.; Periasamy, M. Org. Lett. 1999, 1,
857.
Typical experimental procedure:
To the solution of 2-pentadecyn-1-ol (1a, 0.224 g, 1 mmol) and tri-
ethylamine (0.505 g, 5 mmol) in CH2Cl2 (5 mL) was added drop-
wise TiCl4 (1.0 M solution in CH2Cl2, 3 mL, 3 mmol) at 0 °C. After
stirring for 1 h at 0 °C, the mixture was quenched with 1 M HCl
aqueous solution and extracted with AcOEt. The organic layers
were washed with brine, dried over Na2SO4, and concentrated in
vacuo. The residue was purified by silica gel column chromatogra-
phy (AcOEt/Hex = 1/10) to yield 2-pentadecynal (2a, 0.20 g) in
90% yield.
(5) a) Miklos, J. Polyhedron 1994, 13, 445. b) Veliev, M. G.;
Guseinov, M. M. Synthesis 1980, 461.
(6) In contrast to 3-dodecyn-2-ol, a highly reactive propargylic
secondary alcohol, n-C6H13C C-CH(Ph)OH, was partially
oxidized to the corresponding ketone (n-C6H13C C-C(O)Ph)
in 40% yield along with the starting material under the
standard reaction conditions.
(7) a) Mukaiyama, T.; Sato, Hanna, J. Chem. Lett. 1973, 1041.
b) Fürstner, A.; Bogdanovic, B. Angew. Chem., Int. Ed. Engl.
1996, 35, 2442.
Acknowledgement
This work was supported by Grants-in-Aid for Scientific Research
(Nos. 12305058 and 10208208) from the Ministry of Education,
Science, Sports, and Culture, Government of Japan.
Article Identifier:
1437-2096,E;2001,0,09,1421,1422,ftx,en;Y12801ST.pdf
Synlett 2001, No. 9, 1421–1422 ISSN 0936-5214 © Thieme Stuttgart · New York