T. Pundt et al. / Tetrahedron Letters 48 (2007) 2745–2747
2747
8. For a review of the synthesis of carbacycles by [3+3]
cyclizations of 1,3-bis(silyl enol ethers) with 1,3-dielectro-
philes, see: Feist, H.; Langer, P. Synthesis 2007, 327.
9. Purrington, S. T.; Bumgardner, C. L.; Lazaridis, N. V.;
Singh, P. J. Org. Chem. 1987, 52, 4307.
with BBr3 and subsequent addition of an aqueous solu-
tion of potassium tert-butanolate afforded the novel
fluorinated dibenzo[b,d]pyran-6-ones 6a and 6b in good
yields, respectively (Scheme 3).
10. Xu, Z.-Q.; DesMarteau, D. D.; Gotoh, Y. J. Chem. Soc.,
Chem. Commun. 1991, 179.
11. Xiao, J.-C.; Shreeve, J. M. J. Fluorine Chem. 2005, 126,
475, and references cited therein.
12. Molander, G. A.; Cameron, K. O. J. Am. Chem. Soc.
1993, 115, 830.
We have reported a new and regioselective synthesis of
functionalized 4-fluorophenols based on [3+3] cycliza-
tions of 1,3-bis(silyl enol ethers) with novel 2-fluoro-3-
silyloxy-2-en-1-ones.
13. General procedure for the synthesis of aryl fluorides 5: To a
CH2Cl2 solution (2 mL/1 mmol of 3) of 3 (10.0 mmol) was
added 4 (10.0 mmol) and, subsequently, TiCl4 (1.1 mL,
10.0 mmol) at ꢀ78 ꢁC. The temperature of the solution
was allowed to warm to 20 ꢁC during 14 h with stirring.
To the solution was added hydrochloric acid (10%, 20 mL)
and the organic and the aqueous layer were separated. The
latter was extracted with CH2Cl2 (3 · 20 mL). The com-
bined organic layers were dried (Na2SO4), filtered and the
filtrate was concentrated in vacuo. The residue was
purified by chromatography (silica gel, n-heptane/EtOAc).
Synthesis of methyl 20-fluoro-50-hydroxy-[1,10;30,100]ter-
phenyl-40-carboxylate (5f). Starting with 3b (0.630 g,
2.0 mmol), 4a (0.520 g, 2.0 mmol) and TiCl4 (0.25 ml,
2.2 mmol), 5f was isolated as a colourless solid (0.528 g,
82%); mp = 114–115 ꢁC; Rf = 0.60 (toluene). 1H NMR
(250 MHz, CDCl3): d = 3.46 (s, 3H, OCH3), 7.12 (d,
4J = 6.6 Hz, 1H, Ar), 7.20–7.50 (m, 8H, Ph), 7.53–7.63 (m,
2H, Ph), 10.64 (s, OH). 13C NMR (75.5 MHZ, CDCl3):
d = 51.9 (OCH3), 111.6 (d, 3J = 1.8 Hz, CCOOCH3),
118.2 (br s, CHAr), 127.4, 127.7, 128.5, 128.6 (CHPh),
128.9 (br s, CHPh), 129.1 (d, 4J = 2.9 Hz, CHPh), 131.1 (d,
2J = 20.5 Hz, CAr), 134.7 (d, 3J = 1.4 Hz, CPh), 135.6 (br s,
Acknowledgements
Financial support by the state of Pakistan (HEC schol-
arships for I.H. and for M.A.Y.) is gratefully
acknowledged.
References and notes
1. (a) Kirsch, P. Modern Fluoroorganic Chemistry; VCH:
Weinheim, 2004; (b) Chambers, R. D. Fluorine in Organic
Chemistry; Blackwell Publishing CRC Press, 2004; (c)
Fluorine in Bioorganic Chemistry; Filler, R., Kobayasi, Y.,
Yagupolskii, L. M., Eds.; Elsevier: Amsterdam, 1993; (d)
Hudlicky, M. Chemistry of Organic Fluorine Compounds;
Ellis Horwood: Chichester, 1992; (e) Filler, R. Fluorine
Containing Drugs in Organofluorine Chemicals and Their
Industrial Application; Pergamon: New York, 1976, Chap-
ter 6.
2. Reviews: (a) Tredwell, M.; Gouverneur, V. Org. Biomol.
Chem. 2006, 4, 26; (b) Ma, J.-A.; Cahard, D. Chem. Rev.
2004, 104, 6119; (c) Singh, R. P.; Shreeve, J. M. Synthesis
2002, 17, 2561; (d) Taylor, S. D.; Kotoris, C. C.; Hum, G.
Tetrahedron 1999, 55, 12431; (e) Purrington, S. T.; Kagen,
B. S.; Patrick, T. B. Chem. Rev. 1986, 86, 997.
3. Reviews: (a) Nyffeler, P. T.; Duron, S. G.; Burkart, M. D.;
Vincent, S. P.; Wong, C.-H. Angew. Chem. 2005, 117, 196;
Angew. Chem., Int. Ed. 2005, 44, 192; (b) Singh, R. P.;
Shreeve, J. M. Acc. Chem. Res. 2004, 37, 31.
4. Banks, R. E.; Besheesh, M. K.; Mohialdin-Khaffaf, S. N.;
Sharif, I. J. Chem. Soc., Perkin Trans. 1 1996, 2069.
5. Stavber, S.; Jereb, M.; Zupan, M. Synlett 1999, 9, 1375.
6. Chan, T.-H.; Brownbridge, P. J. Am. Chem. Soc. 1980,
102, 3534.
C
Ph), 135.9 (d, 2J = 17.6 Hz, CAr), 150.0 (d, 1J = 238.3 Hz,
CF), 157.4 (d, 4J = 2.4 Hz, COH), 170.6 (4J = 2.4 Hz,
COOCH3). 19F NMR (235 MHz, Cl3CF): d = ꢀ127.6
(CF). IR (Nujol, cmꢀ1): m ¼ 1669 (m), 1616 (m), 1601 (m),
~
1336 (m), 1254 (m), 1222 (m), 1208 (m), 1114 (m). MS (EI,
70 eV): m/z (%) = 322 (M+, 62), 291 (30), 290 (100), 262
(34), 233 (48). HRMS (EI, 70 eV): calcd for C20H15FO3
(M+): 322.09997; found: 322.09939. All products gave
satisfactory spectroscopic and analytical and/ or high
resolution mass data.
14. CCDC-634352 contains all crystallographic details of this
publication and is available free of charge at www.ccdc.
the following address: Cambridge Crystallographic Data
Centre, 12 Union Road, GB-Cambridge CB21EZ; fax:
(+44)1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
7. For a review of 1,3-bis(silyl enol ethers) in general, see:
Langer, P. Synthesis 2002, 441.