LETTER
Oxidation of Alcohols with Ion-Supported (Diacetoxyiodo)benzenes
1255
N-[3-(4′-Iodophenoxy)-1-propyl]-N,N,N-trimethyl-
2 H), 3.28 (s, 9 H), 3.67 (t, J = 8.4 Hz, 2 H), 4.13 (t, J = 5.5
Hz, 2 H), 6.96 (d, J = 9.1 Hz, 2 H), 8.00 (d, J = 9.1 Hz, 2 H);
δ (anion TsO–) = 2.31 (s, 3 H), 7.12 (d, J = 8.2 Hz, 2 H), 7.71
(d, J = 8.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 20.24,
21.43, 23.03, 53.44, 64.12, 64.68, 111.79, 116.98, 126.35,
129.23, 137.09, 138.19, 142.44, 160.76, 176.63. ESI-
HMRS: m/z calcd for C16H25NI [M+]:438.0772; found:
438.0760.
ammonium 4′′-Methylbenzenesulfonate: mp 222–226 °C.
IR (KBr) 1285, 1010, 816 cm–1. 1H NMR (400 MHz,
CDCl3): δ = 2.12–2.19 (m, 2 H), 2.29 (s, 3 H), 3.08 (s, 9 H),
3.46 (t, J = 8.3 Hz, 2 H), 4.02 (t, J = 6.0 Hz, 2 H), 6.80 (d,
J = 9.0 Hz, 2 H), 7.12 (d, J = 7.9 Hz, 2 H), 7.47 (d, J = 7.9
Hz, 2 H), 7.61 (d, J = 9.0 Hz, 2 H). 13C NMR (100 MHz,
DMSO): δ = 20.74, 22.42, 52.25, 62.84, 64.84, 83.53,
117.29, 125.44, 128.00, 137.51, 138.01, 145.80, 158.04.
HRMS (APPI): m/z calcd for C12H19ONI [M+]: 320.0506;
found: 320.0499.
Typical Procedure for the Preparation of N-Methyl-N-
[3-(4′-diacetoxyiodo)phenyl-1-propyl]pyrrolidinium 4′′-
Methylbenzenesulfonate (IS-DIB A): To a solution of
N-methyl-N-[3-(4′-iodophenyl)-1-propyl]pyrrolidium 4′′-
methylbenzenesulfonate (5 mmol, 2.50 g) in AcOH (50 mL)
was added portionwise NaBO3·4H2O (10 equiv, 50 mmol,
7.69 g). The mixture was stirred for 15 h at 45 °C. After the
reaction, the reaction mixture was concentrated in vacuo,
then the residue was dissolved in H2O (50 mL), and the
obtained mixture was washed with Et2O (50 mL) once.
Then, the aqueous layer was extracted with CHCl3 (5 × 30
mL). The organic layer was dried over Na2SO4. Removal of
the solvent under reduced pressure afforded N-methyl-N-
[3-(4′-diacetoxyiodo)-phenyl-1-propyl]pyrrolidium 4′′-
methylbenzenesulfonate in the range of 60–70% yields
(counteranion; TsO–/AcO– = 1:1; IS-DIB A). The
(9) McKillop, A.; Kemp, D. Tetrahedron 1989, 45, 3299.
(10) General Procedure for the Oxidation of Alcohols with IS-
DIB A, B, and C in the Presence of TEMPO: To a solution
of IS-DIB A, B, or C (1.5 equiv, 0.75 mmol) in CH2Cl2 (2
mL) were added alcohol (0.5 mmol) and TEMPO (10 mol%,
0.05 mmol). Then, the reaction mixture was stirred for 2 h at
r.t. Then, the reaction mixture was concentrated in vacuo,
H2O (20 mL) was added to the residue, and the aqueous layer
was extracted with Et2O (3 × 20 mL). The organic layer was
dried over Na2SO4. Removal of the solvent under reduced
pressure afforded the product (ketone or aldehyde), and
purity of the product was estimated by 1H NMR
spectroscopy. On the other hand, the aqueous layer was
extracted with CHCl3 three times (3 × 20 mL). Then, the
organic layer was washed with aq Na2SO3 and brine. The
organic layer was dried over Na2SO4, and removal of the
solvent under reduced pressure afforded ion-supported
iodobenzene (recovery rate: 75–90%).
Typical Procedure for the Regeneration of N-methyl-N-
[3-(4′-diacetoxyiodo)phenyl-1-propyl]pyrrolidinium 4′′-
Methylbenzenesulfonate (IS-DIB A): To a solution of N-
methyl-N-[3-(4′-iodophenyl)-1-propyl]pyrrolidinium 4′′-
methylbenzenesulfonate (5 mmol, 2.50 g) in AcOH (50 mL)
was added portionwise NaBO3·4H2O (10 equiv, 50 mmol,
7.69 g). The mixture was stirred for 15 h at 45 °C. After the
reaction, the reaction mixture was concentrated, and H2O
(20 mL) was added to the residue. Then the aqueous solution
was washed with H2O once, and then extracted with CHCl3
five times (3 × 30 mL). The organic layer was dried over
Na2SO4. Then, removal of the solvent at 45 °C under
reduced pressure afforded N-methyl-N-[3-(4′-diacetoxy-
iodo)phenyl-1-propyl]pyrrolidinium 4′′-methylbenzene-
sulfonate (TsO–/AcO– = 1:1). The counteranion was
completely converted into the tosylate anion by the stirring
treatment of the obtained IS-DIB A with PTSA·H2O (1.0
equiv) in MeCN (20 mL) at r.t. overnight. Then the solvent
was removed and, and H2O (20 mL) was added to the
residue. The aqueous layer was washed with Et2O and then
extracted with CHCl3 (3 × 30mL). Finally, removal of the
solvent gave the regenerated IS-DIB A.
counteranion was completely converted into the tosylate
anion by the stirring treatment of the obtained IS-DIB A with
PTSA·H2O (1.0 equiv) in MeCN (20 mL) at r.t. overnight.
Then the solvent was removed, and H2O (20 mL) was added
to the residue. The aqueous layer was washed with Et2O and
then extracted with CHCl3 (3 × 30 mL). Finally, removal of
the solvent gave IS-DIB A. IS-DIB B and C were prepared
from pre-B and pre-C in the range of 60–70% yields,
respectively, by the same procedure. The purity of IS-DIB
A, B, and C was estimated to be nearly 90% by 1H NMR
spectroscopy, due to containing a trace amount of pre-A,
pre-B, and pre-C, respectively.
N-Methyl-N-[3-(4′-diacetoxyiodo)phenyl-1-propyl]-
pyrrolidinium 4′′-Methylbenzenesulfonate (IS-DIB A):
viscous oil. IR (neat): 1646, 1556, 1272, 799 cm–1. 1H NMR
(400 MHz, CDCl3): δ (cation) = 2.00 (s, 6 H), 2.06–2.29 (m,
6 H), 2.78 (t, J = 7.8 Hz, 2 H), 3.14 (s, 3 H), 3.54–3.73 (m, 6
H), 7.36 (d, J = 8.6 Hz, 2 H), 7.99 (d, J = 8.6 Hz, 2 H); δ
(anion TsO–) = 2.35 (s, 3 H), 7.17 (d, J = 8.2 Hz, 2 H), 7.77
(d, J = 8.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
δ = 20.28, 21.50, 21.80, 25.27, 31.83, 48.34, 63.47, 64.33,
118.75, 125.68, 128.66, 131.08, 135.11, 139.61, 143.31,
144.49, 176.46. ESI-HMRS: m/z calcd for C18H27O4NI [M+]:
448.0979; found: 448.0967.
Regenerated IS-DIB B and C were prepared from recovered
N-methyl-N-[3-(4′-iodophenoxy)-1-propyl]pyrrolidinium
4′′-methylbenzenesulfonate (pre-B), and N-[3-(4′-
N-Methyl-N-[3-(4′-diacetoxyiodo)phenoxy-1-propyl]-
pyrrolidinium 4′′-Methylbenzenesulfonate (IS-DIB B):
viscous oil. IR (neat): 1650, 1583, 1275, 1010, 823 cm–1. 1H
NMR (400 MHz, CDCl3): δ (cation) = 1.98 (s, 6 H), 2.18–
2.29 (m, 6 H), 3.17 (s, 3 H), 3.59–3.74 (m, 6 H), 4.13 (t,
J = 5.6 Hz, 2 H), 6.93 (d, J = 9.1 Hz, 2 H), 7.97 (d, J = 9.1
Hz, 2 H); δ (anion TsO–) = 2.31 (s, 3 H), 7.12 (d, J = 8.2 Hz,
2 H), 7.73 (d, J = 8.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
δ = 20.28, 21.58, 22.03, 23.85, 48.46, 61.51, 64.51, 64.85,
111.67, 117.03, 125.66, 128.66, 137.02, 138.20, 143.32,
160.77, 176.43. ESI-HMRS: m/z calcd for C18H27O5NI [M+]:
464.0928; found: 464.0919.
iodophenoxy)-1-propyl]-N,N,N-trimethylammonium 4′′-
methylbenzenesulfonate (pre-C), respectively, by the same
method and conditions.
Most of ketones and aldehydes in the present study are
commercially available, and they are identified with
authentic samples, except for the following products.
1-(5′-Methylfuran-2′-yl)-1-pentanone (2d): oil. IR (neat):
3121, 2931, 2827, 1671, 1518, 1452, 876 cm–1. 1H NMR
(400 MHz, CDCl3): δ = 0.94 (t, J = 7.5 Hz, 3 H), 1.39 (sext,
J = 7.5 Hz, 2 H), 1.69 (quin, J = 7.5 Hz, 2 H), 2.39 (s, 3 H),
2.75 (t, J = 7.5 Hz, 2 H), 6.14 (d, J = 3.4 Hz, 1 H), 7.09 (d,
J = 3.4 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 13.15,
13.33, 21.76, 26.11, 37.17, 108.10, 118.22, 150.84, 156.84,
188.40. ESI-HMRS: m/z calcd for C10H15O2 [M + H]:
167.1067; found: 167.1065.
3-[4′-(Diacetoxyiodo)phenoxy]-1-propyl-N,N,N-tri-
methylammonium 4′′-Methylbenzenesulfonate (IS-DIB
C): viscous oil. IR (neat): 1650, 1243, 1040, 812 cm–1.
1H NMR (400 MHz, CDCl3): δ = 1.98 (s 6 H), 2.30–2.35 (m
© Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 1250–1256