R. L. Garrell and A. K. Tucker-Schwartz
Device (SQUID) magnetometer. Transmission electron microscopy
(TEM) images were taken on a FEI CM120 operating at 120 kV. Reac-
tion conversions and selectivities were quantified by using an Agilent
6890–5975 GC/MS with autosampler, equipped with a HP-5 column.
TEM images, particle recycling tables, particle leaching studies, experi-
mental procedures for synthesis of bare Fe3eO4 particles and Cu/C, and
detailed spectroscopic data for all isolated compounds are contained in
the Supporting Information.
uct, and Et3NH+, Na+ salts: 399.17 (17) [M++Na+2H], 377.19 (100)
[M++2H], 194.06 (15) [CgH13NO4P+], 102.13 (30) [C6H10N+]. MS
ACHTUNGTRENNUNG(ESI)
calcd for C15H28N4O5P [M++2H]=377.1948; found 377.1945. Note: See
Supporting Information for high-resolution mass spectrum with assigned
peaks.
Azide-coated particles (4): A 14.8 mL glass vial was charged with of 1
(600 mg), crushed bare Fe3O4 nanoparticles (600 mg), chloroform (6 mL),
and methanol (0.6 mL). The vial was tightly capped and the mixture soni-
cated for 2 h at room temperature. The resulting particles were separated
by using a hand-held rare-earth magnet and the supernatant decanted.
The particles were washed three times with methanol and dried in a
vacuum desicator to yield 4 as a light brown powder. Azide loadings, de-
termined by elemental analysis of the nitrogen content, ranged from
2.40–2.93 mmolgÀ1. IR (KBr): n˜ =2958, 2933, 2870, 2111, 1633, 1066,
Diethyl 3-azidopropylphosphonate: A 100 mL round-bottom flask was
charged with diethyl 3-bromopropylphosphonate (10.1 mmol), dry NaN3
(20.2 mmol), and dry acetone (15 mL), and refluxed under argon for
24 h. The reaction mixture was filtered over a pad of celite and the celite
washed several times with dry acetone. The organic liquid was concen-
trated in vacuo to give
a
clear/light brown oil (97%). 1H NMR
(400 MHz, CDCl3, 258C): d=4.09 (m, 4H; CH2), 3.37 (t, 3J
A
580 cmÀ1
.
3
6.40 Hz, 2H; CH2N3), 1.67 (m, 4H; CH2), 1.32 ppm (t, J
U
Catalyst 5a made by using Approach A: A 10 mL round-bottom flask
was charged with 4 (1 equiv N3, typically 0.70 mmol N3), 2 (1.1 equiv,
0.77 mmol), CuSO4·6H2O (0.05 equiv, 0.04 mmol), sodium ascorbate
(0.15 equiv, 0.11 mmol), Et3N (2 equiv, 1.40 mmol), and degassed 1:1 tBu/
H2O (3 mL). The suspension was stirred under ambient conditions at
room temperature for 24 h. The solvent was then removed in vacuo and
the particles were washed three times with dichloromethane/diethyl ether
(1:1) and then three times with diethyl ether using a hand-held rare-earth
magnet to separate the particles after each wash. The particles were then
dried in a vacuum desicator to yield a light brown powder. TEMPO load-
ings determined by elemental analysis of the nitrogen content range from
0.71–1.08 mmolgÀ1. IR (KBr): n˜ =2993, 2977, 2935, 2854, 1643, 1066,
6H; CH3); 13C NMR (100 MHz, CDCl3, 258C): d=61.7 (d, 2J
7 Hz, 2C), 51.6 (d, 2J(C,P)=16 Hz, 2C), 23.6 (d, 2J
22.5 (d, 2J(C,P)=27 Hz, 2C), 16.5 ppm (d, 2J
ACHTUNGTRENNUNG
T
ACHTUNGTRENNUNG
C
ACHTUNGTRENNUNG
(160 MHz, CDCl3, 258C): d=30.7 ppm (s, 1P); IR: n˜ =2993, 2983, 2937,
2910, 2873, 2104, 1444, 1392, 1369, 1350, 1247, 1163, 1097, 1029, 960, 785,
543 cmÀ1
.
3-Azidopropylphosphonic acid (1): Prepared according to a method pre-
viously reported.[17] Briefly, a 100 mL round-bottom flask was charged
with diethyl 3-aizdopropylphosphonate (5 mmol), acetonitrile (20 mL),
and the mixture cooled to À58C with continuous argon purging. TMSBr
(25 mmol) was added dropwise over 10–15 min with continuous argon
purging and vigorous stirring. The reaction mixture was then warmed to
room temperature and stirred under argon for 24 h. The resulting mix-
ture was concentrated in vacuo and then a 9:1 mixture of MeOH/H2O
(10 mL) was added. The resulting solution was stirred at room tempera-
ture for an additional 24 h. The reaction mixture was concentrated in
vacuo, co-evaporated again with dry toluene and then fully dried in a
vacuum desicator overnight to yield a yellow gummy/oil product (99%).
580 cmÀ1
.
Catalyst 5b made by using Approach B: A 14.8 mL glass vial was
charged with 3 (800 mg), crushed bare Fe3O4 nanoparticles (800 mg),
chloroform (8 mL), and methanol (0.8 mL). The vial was tightly capped
and the mixture sonicated for 2 h at room temperature. The resulting par-
ticles were separated by using a hand-held rare-earth magnet and the su-
pernatant decanted and saved. Particles were washed four times with di-
chloromethane/diethyl ether (1:1), and the supernatant saved. Particles
were dried in a vacuum desicator to yield 5b as a dark brown/black
powder. TEMPO loadings determined by elemental analysis of the nitro-
gen content range from 0.30–0.73 mmolgÀ1. The collected supernatant
was concentrated in vacuo to afford 3, which was not attached to the par-
ticles. This material could be reused to make another batch of 5b.
TEMPO loadings determined by elemental analysis of the nitrogen con-
tent range from 0.50–0.93 mmolgÀ1. IR (KBr): n˜ =2993, 2977, 2935, 2854,
1H NMR (400 MHz, CD3OD, 258C): d=3.39 (t, 3J
CH2N3), 1.79 ppm (m, 4H; CH2); 13C NMR (100 MHz, CD3OD, 258C):
d=51.4 (d, 2J(C,P)=17 Hz, 2C), 24.6 (d, 2J
(C,P)=139 Hz, 2C), 22.5 ppm
(d, 2J(C,P)=4 Hz, 2C); 31P NMR (162 MHz, CD3OD, 258C): d=
28.8 ppm (s, 1P); IR: n˜ =2948, 2881, 2842, 2110, 1652, 1250, 1163, 1020,
943 cmÀ1
ACHTUNGTREN(NUGN H,H)=6.64 Hz, 2H;
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
.
2,2,6,6-Tetramethyl-4-(prop-2-ynyloxy)piperidin-1-oxyl (2): An oven-
dried 100 mL round-bottom flask was charged with tBuOK (30 mmol)
and dry THF (20 mL), placed under an argon atmosphere, and cooled to
08C. 4-Hydroxy-TEMPO (23 mmol) was dissolved in dry THF (10 mL),
injected into the flask, and stirred for 1 h at 08C. Propargyl bromide
(30 mmol, 80% in toluene) was added slowly to the flask and the reac-
tion mixture warmed to room temperature and stirred for an additional
24 h. The reaction mixture was opened to air, and de-ionized (DI) H2O
(2 mL) added. The mixture stirred for an additional 15 min and then all
the solvent was removed in vacuo. The resulting viscous liquid was sub-
jected to silica gel flash chromatography by using ethyl acetate/hexanes
(3:7) to yield an orange crystalline solid (65%). IR: n˜ =3439, 3232, 2995,
2973, 2937, 2870, 1631, 1465, 1379, 1365, 1350, 1311, 1269, 1242, 1219,
1176, 1086, 1020, 734, 692, 555 cmÀ1; elemental analysis calcd (>99%)
C12H20NO2: C 68.54, H 9.59, N 6.66; found: C 68.42, H 9.55, N 6.71.
1643, 1066, 580 cmÀ1
General procedure for aerobic oxidation of alcohols by 5a or 5b with
MnII/CuII co-catalysts: In general,
10 mL round-bottom flask was
charged with 5a or 5b (0.05 mmol, 5 mol%), alcohol (1 mmol), Mn-
(NO3)2·6H2O (0.05 mmol), Cu(NO3)2·3H2O (0.05 mmol), and 50% acetic
.
a
A
ACHTUNGTRENNUNG
acid in a,a,a-trifluorotoluene (2 mL). The mixture was sonicated for 15 s
and then heated to 508C in an oil bath under vigorous stirring. The reac-
tion was stirred open to the air at 508C for 1–2.5 h. The catalyst was then
collected at the side of the flask using a held-held rare-earth magnet, and
the supernatant carefully decanted. Particles were then washed three
times with dichloromethane (5 mL) and the collected organics were
washed two times with saturated NaHCO3 (20 mL), two times with DI
H2O (20 mL), dried over Na2SO4, and filtered over a pad of celite. The
organics were then concentrated in vacuo to yield the corresponding car-
bonyl compound.
Phosphonic acid functionalized TEMPO (3): A 25 mL round-bottom
flask was charged with 1 (2 mmol), 2 (2.2 mmol), Cu/C catalyst (224 mg),
and dioxane (3.5 mL). The flask was placed in a 608C oil bath and Et3N
(2.2 mmol) was added while stirring. The flask was capped and stirred for
24 h at 608C. The resulting slurry was filtered over a pad of celite and
the celite washed with methanol. The organics were concentrated in
vacuo to yield an orange oil. The oil was subjected to silica flash chroma-
tography on a very short column, using ethyl acetate to first flush the
column of unreacted alkyne, and then methanol to flush the product
from the column. The collected methanol was concentrated in vacuo to
yield a gummy orange solid (76%). IR: n˜ =3435, 3139, 2976, 2940, 2877,
2678, 1635, 1463, 1379, 1363, 1242, 1219, 1178, 1157, 1083, 1053, 906, 551,
478 cmÀ1. MS (ESI): m/z (%): Product exists as a mixture of pure prod-
General procedure for catalyst recycling experiments using MnII/CuII co-
catalysts: A 10 mL round-bottom flask was charged with 5a or 5b
(0.025 mmol, 5 mol%), benzyl alcohol (0.5 mmol), Mn
ACHTNUGRTNE(NUGN NO3)2·6H2O
(0.025 mmol), Cu(NO3)2·3H2O (0.025 mmol), and 50% acetic acid in
AHCTUNGTRENNUNG
a,a,a-trifluorotoluene (1 mL). The mixture was sonicated for 15 s and
then heated to 508C in an oil bath under vigorous stirring. The reaction
was stirred open to the air at 508C for 1 h. After 1 h, particles were col-
lected at the side of the reaction flask using a hand-held rare-earth
magnet and a 10 uL aliquot was taken for GC/MS analysis. The reaction
medium was carefully decanted and the particles washed two times with
12724
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 12718 – 12726