â-AlkylVinyl(chloro)-λ3-iodanes
J. Am. Chem. Soc., Vol. 120, No. 10, 1998 2281
1-(trimethylsilyl)-1-butyne. By a similar procedure used for 1a, (E)-
3-methyl-1-(trimethylsilyl)-1-butene (220 mg, 1.55 mmol) was treated
with iodosylbenzene (614 mg, 2.79 mmol) and BF3-Et2O (396 mg,
2.79 mmol) in dichloromethane (8 mL) for 5 h at room temperature
under nitrogen. Recrystallization from hexane-dichloromethane gave
the vinyliodonium salt 1c (94 mg, 17%) as colorless crystals: mp 91.5-
92 °C. IR (KBr) 2964, 1563, 1471, 1306, 1095, 740, 681, 651, 522
on the rate constant ks for the substitution reaction of chloride
ion (Table 1). Free carbon-carbon bond rotation allows these
smaller alkyl substituents to adopt a conformation that can avoid
interfering with the incoming nucleophile. The nucleophile is
assumed to approach the vinylic carbon from the direction of
the R-hydrogen atom and may in fact form a stabilizing
hydrogen bond to this R-hydrogen. This hydrogen bond has
been detected in theoretical calculations of the reaction coor-
dinate for SN2 nucleophilic substitution reactions at vinylic
carbon.7a,17
cm-1 1H NMR (CDCl3) δ 7.99 (d, J ) 7.8 Hz, 2H), 7.68 (t, J ) 7.4
.
Hz, 1H), 7.52 (dd, J ) 7.8, 7.4 Hz, 2H), 6.96 (dd, J ) 14.3, 7.0 Hz,
1H), 6.78 (d, J ) 14.3 Hz, 1H), 2.64 (octet, J ) 7.0 Hz, 1H), 1.09 (d,
J ) 7.0 Hz, 6H). HRFAB MS calcd for C11H14I [(M - BF4)+]
273.0140. Found 273.0150. Anal. Calcd for C11H14BF4I: C, 36.71;
H, 3.92. Found: C, 36.45; H, 3.90.
In conclusion, it is now established that the in-plane SN2
substitution occurs at the vinylic carbon of primary vinyl-λ3-
iodane/iodonium substrates.
(E)-3,3-Dimethyl-1-butenyl(phenyl)iodonium Tetrafluoroborate
(1d). (E)-3,3-Dimethyl-1-(trimethylsilyl)-1-butene was prepared in 68%
yield by the hydroalumination-protonolysis22 of 3,3-dimethyl-1-(trim-
ethylsilyl)-1-butyne. By a similar procedure used for 1a, the vinylsilane
(2.07 g, 13.2 mmol) was treated with iodosylbenzene (4.37 g, 19.9
mmol) and BF3-Et2O (2.82 g, 19,9 mmol) in dichloromethane (66 mL)
for 3 h at room temperature under nitrogen. Recrystallization from
hexane-dichloromethane gave the vinyliodonium salt 1d (2.37 g, 48%)
as colorless needles: mp 147-147.5 °C. IR (KBr) 3092, 2964, 1470,
Experimental Section
1H NMR spectra were recorded on a JEOL JNM-FX200 or a Varian
INOVA 500 spectrometer and chemical shifts are given in ppm
downfield from internal TMS. IR and UV spectra were obtained by
JASCO IRA-1 and Shimadzu UV-2200 spectrophotometers, respec-
tively. Mass spectrometers JEOL JMS-SX102A and JMS-DX303HF
were used for MS. Gas chromatography was conducted on a Shimadzu
GC-14B with a DB-1 capillary column (0.25 mm × 30 m). Melting
points were measured on a Yanaco micro-melting-point apparatus and
are not corrected.
Acetonitrile was distilled from calcium hydride. Chloroform of
analytical grade stabilized with 2-methyl-2-butene obtained from TCI
(Tokyo) was used without purification. Other solvents are of the best
grade commercially available. Acetonitrile-d3 containing 99.6 atom
% of D and 0.03% of TMS and CDCl3 (99.9 atom % D) were obtained
from Aldrich. Tetrabutylammonium chloride (TCI) and perchlorate
(Fluka) and tetrmethylammonium chloride (Wako, Osaka) were used
without further purification. 1-Decyne (4b, TCI), 3,3-dimethyl-1-butyne
(4d, TCI), and iodobenzene (5, Wako) were purchased for authentic
samples.
1446, 1263, 1080, 990, 742, 680, 523 cm-1 1H NMR (CDCl3) δ 8.00
.
(d, J ) 8.0, 2H), 7.67 (t, J ) 7.5 Hz, 1H), 7.51 (dd, J ) 8.0, 7.5 Hz,
2H), 6.99 (d, J ) 14.4 Hz, 1H), 6.78 (d, J ) 14.4 Hz, 1H), 1.11 (s,
9H). HRFAB MS calcd for C12H16I [(M - BF4)+] 287.0297. Found
287.0312. Anal. Calcd for C12H16BF4I‚1/4H2O: C, 38.08; H, 4.26.
Found: C, 38.07; H, 4.27.
Product Determination for Reaction of 1b. A sample of 1b (2-5
mg) was dissolved in acetonitrile solution containing the specified
concentrations of tetrabutylammonium chloride and perchlorate and kept
at 25 °C for about 10 half-lives. The amount of the chloride solution
was decided for the chloride to be at least 5 times excess of the substrate.
The reaction mixture was diluted with water, and the products were
extracted 3 times with pentane containing tetradecane (2.5 × 10-6 mol)
for a GC internal standard. The combined pentane layer was washed
with water, dried over MgSO4, and analyzed by GC before and after
concentration. GC MS was examined when necessary.
(E)-1-Propenyl(phenyl)iodonium Tetrafluoroborate (1a). (E)-1-
(Trimethylsilyl)-1-propene was prepared stereoselectively from 3-(tri-
methylsilyl)-1-propene by Fe(CO)3-catalyzed photoisomerization in
27% yield according to a literature procedure.18 To a stirred suspension
of iodosylbenzene (4.70 g, 21.4 mmol) and (E)-1-(trimethylsilyl)-1-
propene (1.22 g, 10.7 mmol) in dichloromethane (67 mL) was added
dropwise BF3-Et2O (3.98 g, 28.1 mmol) at 0 °C under nitrogen, and
the mixture was stirred for 50 h at 0 °C and then for 1 h at room
temperature. The mixture was stirred with a saturated aqueous solution
of sodium tetrafluoroborate (15 g) for 30 min and then extracted with
dichloromethane. The organic layer was concentrated under an aspirator
vacuum to give an oil, which was washed several times with hexane
by decantation at -78 °C. Recrystallization from hexane-dichlo-
romethane gave the vinyliodonium salt 1a (1.11 g, 31%) as colorless
crystals: mp 67.5-68 °C. IR (KBr) 3030, 1472, 1441, 1063, 992,
Pure samples of 3b23 and 4b were isolated by preparative GC (20%
silicone GE SF-96, 1 m) from a large-scale reaction of 1b. 3b: IR
(CHCl3) 2935, 2850, 1620, 1570, 1465, 1435, 1050, 1005, 990 cm-1
.
1H NMR (CDCl3) δ 6.01 (dt, J ) 7.3, 1.5 Hz, 1H), 5.75 (q, J ) 7.3
Hz, 1H), 2.22 (dq, J ) 1.5, 7.3 Hz, 2H), 1.50-1.15 (12H), 0.89 (t, J
) 6.5 Hz, 3H). 4b: 1H NMR (CDCl3) δ 2.18 (dt, J ) 2.6, 6.8 Hz,
2H), 1.93 (t, J ) 2.6 Hz, 1H), 1.60-1.20 (12H), 0.88 (t, J ) 6.6 Hz,
3H).
Products of Reaction of 1d. Reaction products of 1d were
determined by GC in the same way as those of 1b by comparison with
the authentic samples of 4d and 5. No sign of formation of 3d was
found.
NMR Determination of Product Ratio. Reaction was carried out
at the substrate concentration of 2 mmol dm-3 in acetonitrile-d3
containing 0.01 mol dm-3 tetramethylammonium chloride and 0.03%
TMS in an NMR tube. For the reactions of 1a and 1c, the tube was
sealed by fusion to avoid evaporation of the products, but it was only
stoppered with a cap for 1d. The required amount (0.2 mL) of the
stock solution of 1 in chloroform (0.01 mol dm-3) was placed in a
flask, the solvent was completely removed under vacuum, and 1 mL
of the ammonium chloride solution in acetonitrile-d3 was added. The
solution was transferred in an NMR tube and kept at 25 °C for 5 h and
subjected to the NMR measurements. From the relative integral
intensities of the olefinic and the acetylenic signals or those of the
735, 680, 522 cm-1 1H NMR (CDCl3) δ 8.01 (d, J ) 8.0 Hz, 2H),
.
7.67 (t, J ) 7.3 Hz, 1H), 7.51 (dd, J ) 8.0, 7.3 Hz, 2H), 7.03 (dq, J
) 13.7, 6.8 Hz, 1H), 6.80 (dq, J ) 13.7, 1.4 Hz, 1H), 2.05 (dd, J )
6.8, 1.4 Hz, 3H). HRFAB MS calcd for C9H10I [(M - BF4)+] 244.9827.
Found 244.9817. Anal. Calcd for C9H10BF4I: C, 32.57; H, 3.04.
Found: C, 32.51; H, 2.98.
(E)-1-Decenyl(phenyl)iodonium Tetrafluoroborate (1b). The BF3-
catalyzed silicon-iodonium exchange reaction between (E)-1-(trim-
ethylsilyl)-1-decene and iodosylbenzene was carried out in the same
way as described previously.19 The yield of 1b was 72%.
(E)-3-Methyl-1-butenyl(phenyl)iodonium Tetrafluoroborate (1c).
(E)-3-Methyl-1-(trimethylsilyl)-1-butene was prepared in 69% yield by
the benzenesulfinic acid catalyzed isomerization20 of the (Z) isomer,
which was obtained by hydroalumination-protonolysis21 of 3-methyl-
(20) Ochiai, M.; Takaoka, Y.; Ukita, T.; Nagao, Y.; Fujita, E. J. Org.
Chem. 1989, 54, 2346.
(21) (a) Miller, R. B.; McGarvey, G. J. Org. Chem. 1978, 43, 4424. (b)
Zweifel, G.; Lewis, W. J. Org. Chem. 1978, 43, 2739. (c) Eisch, J. J.; Rhee,
S.-G. J. Am. Chem. Soc. 1975, 97, 4673. (d) Uchida, K.; Utimoto, K.;
Nozaki, H. J. Org. Chem. 1976, 41, 2215.
(22) Eisch, J. J.; Foxton, M. W. J. Org. Chem. 1971, 36, 3520.
(23) Miyano, S.; Izumi, Y.; Fujii, K.; Ohno, Y.; Hashimoto, H. Bull.
Chem. Soc. Jpn. 1979, 52, 1197.
(17) Yamataka, H.; Nagase, S.; Okuyama, T.; Ochiai, M. Unpublished
results.
(18) Mizuno, K.; Daimon, S.; Nakanishi, K.; Isagawa, K.; Otsuji, Y.
Chem. Express 1992, 7, 209.
(19) Ochiai, M.; Sumi, K.; Takaoka, Y.; Kunishima, M.; Nagao, Y.;
Shiro, M.; Fujita, E. Tetrahedron 1988, 44, 4095.