Organic & Biomolecular Chemistry
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previously reported intramolecular hydroalkoxylation as well 129.1, 126.0, 75.9, 62.7, 34.6, 32.9, 26.0, 21.0, 20.1; IR (neat,
as diverse transformations such as the deiodination of cm−1): 2937; HRMS (ESI, m/z) Calcd for C13H18NaO [M + Na]+:
iodoethers, the reductive ring opening of iodoethers and cyclic 213.1255, found 213.1259.
ethers, and the formal hydrogenation of a γ-hydroxy phenyl-
substituted alkene. The PhSiH3–I2 protocol causes the iodina- oil; H NMR (400 MHz, CDCl3): δ 7.40–7.34 (m, 2H), 7.06–7.01
2-Methyl-2-(4-fluorophenyl)tetrahydrofuran (5b). Colorless
1
tion of alcohols.
(m, 2H), 3.75–3.69 (m, 1H), 3.45 (ddd, 1H, J = 11.6, 10.6, 3.2
Hz), 2.28–2.21 (m, 1H), 1.78–1.41 (m, 5H), 1.37 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 161.6 (d, J = 244.4 Hz), 141.1 (d, J =
2.8 Hz), 127.5 (d, J = 7.6 Hz), 115.0 (d, J = 21.0 Hz), 75.5, 62.6,
34.6, 32.5, 25.9, 20.0; IR (neat, cm−1): 2939; HRMS (DART, m/z)
Calcd for C12H19FNO [M + NH4]+: 212.1451, found 212.1476.
Tandem deiodination/reductive ring opening/iodination
reaction from iodoether A to acyclic iodide E. I2 (8.4 mg,
0.033 mmol) and PhSiH3 (24 μl, 0.19 mmol) were added to a
solution of 2a (50 mg, 0.17 mmol) in CH2Cl2 (0.5 ml) at room
temperature. After stirring 12 h, the reaction mixture was
quenched with H2O and extracted with Et2O (three times). The
combined organic layer was washed with brine, dried over
MgSO4 and concentrated under reduced pressure. The crude
mixture was purified by silica gel column chromatography
(hexane/Et2O = 100 : 1) to afford 2e (39 mg, 82%) as colorless
oil.
Conclusions
The deiodination of iodoether A was rationalized by the deiodi-
native ring opening/intramolecular hydroalkoxylation mechan-
ism mediated by PhSiH2I. Stemming from the mechanistic
study, we also found a series of PhSiH2I-mediated reactions
under PhSiH3–I2 and PhSiH3–NIS protocols. Iodoether A and
cyclic ether B as well as alcohol D are converted to acyclic
iodide E under PhSiH3–I2 protocols, whereas iodoether A,
cyclic ether B, and hydroxy alkene C are converted to acyclic
alcohol D under PhSiH3–NIS protocols. These results indicate
that PhSiH2I acts as a silyl iodide species having the properties
of a Lewis acid and an iodide donor and as a hydrosilane
species having the properties of a hydride donor in these reac-
tions. Further studies on the silane–iodine system are ongoing
in our laboratory.
(6-Iodohexan-2-yl)benzene (2e). Yellow oil; 1H NMR
(400 MHz, CDCl3): δ 7.31–7.27 (m, 2H), 7.20–7.16 (m, 3H), 3.13
(td, 2H, J = 6.8, 2.0 Hz), 2.67 (sext, 1H, J = 6.8 Hz), 1.84–1.76
(m, 2H), 1.61–1.53 (m, 2H), 1.43–1.24 (m, 2H), 1.24 (d, 3H, J =
6.8 Hz); 13C NMR (100 MHz, CDCl3): δ 147.3, 128.3, 127.0,
126.0, 39.8, 37.2, 33.6, 28.6, 22.3, 6.9; IR (neat, cm−1): 2957,
2929; HRMS (DART, m/z) Calcd for C12H21IN [M + NH4]+:
306.0719, found 306.0716.
Experimental
General considerations
All reagents were obtained from commercial sources and used
without further purification. Reactions were carried out in a
glass flask with a plastic cap. Column chromatography was
1-(6-Iodohexan-2-yl)-4-methylbenzene (4e). Yellow oil; 1H
NMR (400 MHz, CDCl3): δ 7.11–7.05 (m, 4H), 3.12 (td, 2H, J =
7.2, 2.0 Hz), 2.64 (sext, 1H, J = 6.8 Hz), 2.32 (s, 3H), 1.83–1.80
(m, 2H), 1.60–1.51 (m, 2H), 1.40–1.25 (m, 2H), 1.21 (d, 3H, J =
6.8 Hz); 13C NMR (100 MHz, CDCl3): δ 144.3, 135.3, 129.0,
126.8, 39.3, 37.2, 33.7, 28.7, 22.4, 21.0, 6.9; IR (neat, cm−1):
2927; HRMS (DART, m/z) Calcd for C13H23IN [M + NH4]+:
320.0875, found 320.0873.
performed on silica gel (Cica silica gel 60N). H and 13C NMR
1
were obtained for samples in CDCl3 on a JEOL 400 MHz
spectrometer at room temperature. 1H NMR chemical shifts
are reported in terms of chemical shift (δ, ppm) relative to the
singlet at 7.26 ppm for chloroform. 13C NMR chemical shifts
were fully decoupled and are reported in terms of chemical
shift (δ, ppm) relative to the triplet at 77.0 ppm for CDCl3.
1-Fluoro-4-(6-iodohexan-2-yl)benzene (5e). Yellow oil; 1H
NMR (400 MHz, CDCl3): δ 7.14–7.10 (m, 2H), 6.99–6.95 (m,
2H), 3.13 (t, 2H, J = 7.4 Hz), 2.66 (sext, 1H, J = 6.8 Hz),
Representative procedure
Deiodination of iodoether A. I2 (1.4 mg, 5.6 μmol) and 1.83–1.75 (m, 2H), 1.58–1.53 (m, 2H), 1.38–1.25 (m, 2H), 1.22
PhSiH3 (34 μl, 0.28 mmol) were added to a solution of 2a (d, 3H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3): δ 161.2 (d, J =
(56 mg, 0.19 mmol) in toluene (2 ml) at room temperature. 243.4 Hz), 142.8 (d, J = 2.8 Hz), 128.1 (d, J = 7.6 Hz), 115.2 (d,
After stirring for 30 min, the reaction mixture was quenched J = 21.0 Hz), 39.1, 37.3, 33.5, 28.5, 22.4, 6.8; IR (neat, cm−1):
with sat. Na2S2O3 and extracted with Et2O (three times). The com- 2958; HRMS (DART, m/z) Calcd for C12H20FIN [M + NH4]+:
bined organic layer was washed with brine, dried over MgSO4 324.0624, found 324.0612.
and concentrated under reduced pressure. The crude mixture
(5-Iodopentan-2-yl)benzene (1e). Yellow oil; 1H NMR
was purified by silica gel column chromatography (hexane/Et2O = (400 MHz, CDCl3): δ 7.32–7.28 (m, 2H), 7.21–7.17 (m, 3H), 3.13
100 : 1) to afford 2b (27 mg, 82%) as colorless oil. Analytical data (t, 2H, J = 6.8 Hz), 2.71 (sext, 1H, J = 6.8 Hz), 1.76–1.68 (m, 4H),
of 1b and 2b were consistent with reported data.12
1.26 (d, 3H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3): δ 146.8,
2-Methyl-2-(4-methylphenyl)tetrahydrofuran (4b). Colorless 128.4, 126.9, 126.1, 39.2, 39.0, 31.6, 22.4, 7.1; IR (neat, cm−1):
1
oil; H NMR (400 MHz, CDCl3): δ 7.29 (d, 2H, J = 8.0 Hz), 7.17 2958; HRMS (DART, m/z) Calcd for C11H19IN [M + NH4]+:
(d, 2H, J = 8.0 Hz), 3.74–3.67 (m, 1H), 3.47 (td, 1H, J = 11.6, 4.8 292.0562, found 292.0554.
Hz), 2.35 (s, 3H), 2.28 (dt, 1H, J = 13.6, 3.2 Hz), 1.76–1.36 (m,
Tandem deiodination/reductive ring opening reaction from
5H), 1.36 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 142.2, 136.0, iodoether A to acyclic alcohol D. After a solution of NIS
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