Bun
29.1 (1F, s). nmax(neat)/cm21 2960, 2930, 2860, 1610, 1460, 1435, 1265,
Bun
Bun
+
1
190, 1065, 755, 730. m/z (20 eV) 208 (M , 50%), 165 (100). HRMS: calc.
F2C
for C12H13SF, 208.0722 (M
+
). Found 208.0694.
F2C
H2N
i, ii
F2C
MeS
(67%)
iii
MeS
1
L. G. Sprague, K. B. Baucom, S. F. Sellers and R. A. DuBoisson, in
O
Chemistry of Organic Fluorine Compounds II, ed. M. Hudlicky and
A. E. Pavlath, ACS Monograph 187, American Chemical Society,
Washington, DC, 1995, pp. 729–756.
3a
7 (83%)
2
CHCH -
Scheme 3 Reagents and conditions: i, CF
CH ONO (2 equiv.), MeCN, 0 °C, 0.5 h; ii, aq. NaSMe (3 equiv.), MeCN,
°C to room temp., 1.5 h; iii, aq. TiCl
MeOH–H O, room temp., 2 h
3
CO
2
H (2 equiv.), Me
2
2
3
M. J. Tozer and T. F. Herpin, Tetrahedron 1996, 52, 8619.
2
J. R. McCarthy, P. S. Sunkara, D. P. Matthews, A. J. Bitonti, E. T. Jarvi,
J. F. Sabol, R. J. Resvick, E. W. Huber, W. A. v. d. Donk, G. Yu and
J. Stubbe, in Biomedical Frontiers of Fluorine Chemistry, ed. I. Ojima,
J. R. McCarthy and J. T. Welch, ACS Symposium Series 639, American
Chemical Society, Washington, DC, 1996, ch. 18; P. Bey, J. R.
McCarthy and I. A. McDonald, in Selective Fluorination in Organic and
Bioorganic Chemistry, ed. J. T. Welch, ACS Symposium Series 456,
American Chemical Society, Washington, DC, 1991, pp. 105–133.
0
3
2 2
(2 equiv.), aq. H O (3 equiv.),
2
Bun
Bun
Bun
F2C
MeS
i
ii
F2C
F
S
4 J. Ichikawa, N. Yokota, M. Kobayashi and T. Minami, Synlett, 1993,
186.
XS
8 X = CH2OCOCF3
O
5
J. Ichikawa, M. Kobayashi, N. Yokota, Y. Noda and T. Minami,
Tetrahedron, 1994, 50, 11637; J. Ichikawa, N. Yokota, M. Kobayashi,
K. Amano and T. Minami, Synlett, 1996, 243.
7
9 (82% from 7)
Scheme 4 Reagents and conditions: i, (CF
3 2 3
CO) O (3 equiv.), Et N (3
equiv.), CH Cl , 0 °C, 0.5 h; ii, K CO (6 equiv.), MeOH, 0 °C to reflux,
6
7
J. Ichikawa, M. Kobayashi, Y. Noda, N. Yokota, K. Amano and T.
Minami, J. Org. Chem., 1996, 61, 2763.
o-Substituted b,b-dichloro- and -dibromo-styrenes have recently been
reported to undergo intramolecular cyclization via electrophilic carbe-
noids: M. Topolski, J. Org. Chem., 1995, 60, 5588.
2
2
2
3
2
h
In conclusion, nucleophilic addition–elimination reactions
8
9
(a) J. E. Baldwin, J. Chem. Soc., Chem. Commun., 1976, 734; (b) J. E.
Baldwin, J. Cutting, W. Dupont, L. Kruse, L. Silberman and R. C.
Thomas, ibid., 1976, 736; (c) J. E. Baldwin, R. C. Thomas, L. I. Kruse
and L. Silberman, J. Org. Chem., 1977, 42, 3846.
D. Craig and A. M. Smith, Tetrahedron Lett., 1992, 33, 695; P. Auvray,
P. Knochel and J. F. Normant, Tetrahedron Lett., 1985, 26, 4455; R.
Grigg, J. Kemp, J. F. Malone, S. Rajviroongit and A. Tangthongkum,
Tetrahedron, 1988, 44, 5361. For a related example, see: R. D.
Chambers and M. P. Greenhall, J. Chem. Soc., Chem. Commun., 1990,
1128.
with the b,b-difluorovinylidene moiety allows normally ‘dis-
favoured’ 5-endo-trigonal cyclizations to occur. This cycliza-
tion process affords ring-fluorinated indoles, benzo[b]furans,
and benzo[b]thiophenes in high yields. These ‘anti-Baldwin’
results indicate that some of the unique reactivity of gem-
difluoroalkenes may be derived from a partial single bond
character of the alkene.
We gratefully acknowledge financial support for this re-
search in the form of a grant from the Ministry of Education,
Science, Sports, and Culture, Japan (Grant-in-Aid for Scientific
Research No. 09640641), and Central Glass Co. Ltd. to J. I. We
also thank the Center for Instrumental Analysis KIT for the
measurement of analytical data.
1
0 A. D. Jones and D. W. Knight, Chem. Commun., 1996, 915; Y. Landais
and D. Planchenault, Synlett, 1995, 1191 and references cited therein;
B. H. Lipshutz and T. Gross, J. Org. Chem., 1995, 60, 3572 and
references cited therein; M. Kimura, H. Harayama, S. Tanaka and Y.
Tamaru, J. Chem. Soc., Chem. Commun., 1994, 2531.
1
1 For 5-endo radical cyclizations onto an unsaturated carbon, see T.
Gimisis and C. Chatgilialoglu, J. Org. Chem., 1996, 61, 1908; T. Sato,
N. Chono, H. Ishibashi and M. Ikeda, J. Chem. Soc., Perkin Trans. 1,
Footnotes and References
†
‡
E-mail: ichikawa@che.kyutech.ac.jp
Electrophile-driven cyclizations refer to ring closure initiated by the
1
995, 1115; A. V. R. Rao, A. K. Singh, K. M. Reddy and K. Ravikumar,
J. Chem. Soc., Perkin Trans. 1, 1993, 3171. See, also: D. L. J. Clive and
W. Yang, Chem. Commun., 1996, 1605. For 5-endo radical cyclizations
onto a multiple-bonded, first-row heteroatom, see: Y. Yamamoto, M.
Ohno and S. Eguchi, J. Org. Chem., 1996, 61, 9264 and references cited
therein.
coordination of the double bond in a substrate to an external electrophile
such as I and PhSeCl. Strictly speaking, this type of cyclization does not
seem likely to be an exception to Baldwin’s rules.
2
1
§
3
5a: H NMR (500 MHz, CDCl ): d 0.86 (3H, t, J 7.4 Hz), 1.21 (2H, tq,
J 7.4, 7.4 Hz), 1.53 (2H, tt, J 7.4, 7.4 Hz), 2.34 (3H, s), 2.52 (2H, td, J 7.4
Hz, JHF 0.8 Hz), 7.20 (2H, d, J 8.4 Hz), 7.23 (1H, ddd, J 7.7, 7.7, 1.2 Hz),
1
1
2 M. J. Silvester, Adv. Heterocycl. Chem., 1994, 59, 1; Aldrichim. Acta,
1
991, 24, 31; Organofluorine Chemistry, Principles and Commercial
7.28 (1H, ddd, J 7.7, 7.7, 1.4 Hz), 7.33 (1H, dd, J 7.7, 1.2 Hz), 7.73 (2H, d,
1
3
Applications, ed. R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum
Press, New York, 1994.
3 J. Ichikawa, T. Minami, T. Sonoda and H. Kobayashi, Tetrahedron
Lett., 1992, 33, 3779; see also: J. Ichikawa, M. Fujiwara, H. Nawata, T.
Okauchi and T. Minami, Tetrahedron Lett., 1996, 37, 8799.
J 8.4 Hz), 8.08 (1H, d, J 7.7 Hz). C NMR (126 MHz, CDCl
d, JCF 3 Hz), 21.5, 22.1, 30.5, 99.7 (d, JCF 11 Hz), 114.4, 118.9 (d, JCF
Hz), 124.0, 124.0 (d, JCF 4 Hz), 126.8, 128.1 (d, JCF 6 Hz), 129.8, 130.6,
3
): d 13.6, 21.3
(
7
34.7, 145.2, 147.4 (d, JCF 276 Hz). 9F NMR (470 MHz, CDCl
1
1
2
1
–C F ): d
3 6 6
9.1 (1F, s). nmax(neat)/cm21 2960, 2930, 2860, 1660, 1455, 1395, 1190,
+
14 For the synthesis of fluoroindoles, see H. F. Hodson, D. J. Madge,
A. N. Z. Slawin, D. A. Widdowson and D. J. Williams, Tetrahedron,
1994, 50, 1899. For the synthesis of fluoropyrroles, see Z.-M. Qiu and
D. J. Burton, Tetrahedron Lett., 1995, 36, 5119; J. Leroy and C.
Wakselman, Tetrahedron Lett., 1994, 35, 8605 and references cited
therein.
180, 745, 690, 665. m/z (20 eV) 345 (M , 100%), 190 (68), 148 (92).
+
HRMS: calc. for C19
H
20
O
2
SNF, 345.1199 (M ). Found, 345.1188.
1
¶
Selected data for 6: H NMR (500 MHz, CDCl
3
): d 0.94 (3H, t, J 7.4 Hz),
1.39 (2H, tq, J 7.4, 7.4 Hz), 1.66 (2H, tt, J 7.4, 7.4 Hz), 2.57 (2H, td, J 7.4
Hz, JHF 1.0 Hz), 7.19–7.25 (2H, m), 7.32–7.36 (1H, m), 7.40–7.45 (1H, m).
1
3
3
C NMR (126 MHz, CDCl ): d 13.8, 21.0 (d, JCF 3 Hz), 22.4, 30.7 (d, JCF 2
1
5 For the synthesis of fluorobenzo[b]furans, see: D. H. R. Barton, R. H.
Hesse, G. P. Jackman and M. M. Pechet, J. Chem. Soc., Perkin Trans.
1, 1977, 2604. For the synthesis of fluorofurans, see A. K. Forrest and
P. J. O’Hanlon, Tetrahedron Lett., 1995, 36, 2117; K. Burger and B.
Helmreich, J. Chem. Soc., Chem. Commun., 1992, 348; H. L. Sham and
D. A. Betebenner, J. Chem. Soc., Chem. Commun., 1991, 1134.
6 R. N. Young, J. Y. Gauthier and W. Coombs, Tetrahedron Lett., 1984,
25, 1753.
Hz), 90.6 (d, JCF 12 Hz), 110.8, 119.2 (d, JCF 6 Hz), 123.1 (d, JCF 4 Hz),
23.2, 129.3 (d, JCF 3 Hz), 147.1, 157.1 (d, JCF 278 Hz). 9F NMR (470
1
1
): d 42.0 (1F, s). nmax (neat)/cm21 2960, 2940, 2860,
MHz, CDCl –C
3 6
F
6
+
1
1
∑
675, 1455, 1380, 1295, 1260, 1185, 1140, 740. m/z (20 eV) 192 (M , 43%),
+
49 (100). HRMS: calc. for C12H13OF, 192.0950 (M ). Found, 192.0918.
This formation of benzothiophenes is favoured by Baldwin’s rules since
1
1
second-row elements are permitted 5-endo-trigonal processes [ref. 8(b)].
1
Selected data for 9: H NMR (500 MHz, CDCl
.39 (2H, tq, J 7.5, 7.5 Hz), 1.64 (2H, tt, J 7.5, 7.5 Hz), 2.75 (2H, td, J 7.5
Hz, JHF 1.3 Hz), 7.28 (1H, ddd, J 7.6, 7.6, 1.4 Hz), 7.35 (1H, ddd, J 7.6, 7.6,
3
): d 0.94 (3H, t, J 7.5 Hz),
7 For the synthesis of fluorobenzo[b]thiophenes, see; P. Nussbaumer, G.
Petrenyi and A. St u¨ tz, J. Med. Chem., 1991, 34, 65. For the synthesis of
fluorothiophenes, see K. Burger and B. Helmreich, Heterocycles, 1994,
1
1
3
0
.9 Hz), 7.58 (1H, d, J 7.9 Hz), 7.64 (1H, d, J 7.9 Hz). C NMR (126 MHz,
CDCl ): d 13.8, 22.5, 23.6, 31.0 (d, JCF 2 Hz), 115.5 (d, JCF 10 Hz), 121.5
d, JCF 6 Hz), 122.6, 124.0 (d, JCF 4 Hz), 124.6, 131.3 (d, JCF 2 Hz), 136.8
d, JCF 6 Hz), 159.2 (d, JCF 289 Hz). 19F NMR (470 MHz, CDCl
–C ): d
3
9, 819.
3
(
(
3
6 6
F
Received in Cambridge, UK, 7th May 1997; 7/03110F
1538
Chem. Commun., 1997