Photochemical Synthesis of Aldehydes in the Solid Phase
J . Org. Chem., Vol. 67, No. 8, 2002 2681
CDCl3) δ 183.22, 182.81, 157.48, 145.87, 137.23, 135.68, 134.89,
134.13, 133.79, 133.49, 132.68, 128.55 (2), 128.38, 128.18,
128.04, 127.33, 126.62, 125.93, 123.38, 75.28, 63.05, 63.04,
32.79, 30.56, 30.22, 29.53, 29.49 (2), 29.43 (2), 25.75. Anal.
Calcd for C32H36O4: C, 79.31; H, 7.49; Found: C, 79.82; H,
7.42.
P r ep a r a tion of 85% Loa d ed P olym er 11 (F LP ). To a 50
mL round-bottom flask were added 1.64 g of ArgoGel resin
(0.66 mmol of NH2 groups) and 30 mL of dry THF. The resin
beads were stirred for 15 min to allow them to swell. A solution
of 0.390 g (0.655 mmol) of 10 in 5 mL of THF was added to
the beads. The flask was wrapped with aluminum foil and
stirred for 48 h, after which time the yellow beads were
collected by vacuum filtration. The beads were stirred with
20 mL of THF for 45 min, vacuum filtered, vacuum dried, and
weighed. This process was repeated until the washings were
colorless and the mass of the dried beads was constant (two
more times). The faintly yellow filtrate and washings were
combined, and the solvent was removed in a rotary evaporator
under reduced pressure leaving a residue that contained 57
mg (0.096 mmol) of unreacted 10 and 64 mg (0.56 mmol) of
NHS. Both of these quantities show indirectly that 85% of AQ
10 reacted with the resin. Reacting the resin with a 10% excess
of 10 did not increase the loading.
P r ep a r a tion of 50% Loa d ed P olym er 11 (P LP ). The
above procedure was followed starting with 1.68 g of resin (0.67
mmol of NH2 groups) and 200 mg of 10 (0.336 mmol). The
residue from the filtrate and washings contained only a trace
of 10 and 39 mg (0.34 mmol) of NHS showing that the reaction
occurred quantitatively and that the resin was 50% loaded.
Gen er a l P r oced u r e for th e P h otolysis of th e Resin .
Into a 50 mL round-bottom flask was introduced F LP or P LP
(200-300 mg) and 50 mL of 90% aqueous methanol. The
mixture was deoxygenated with N2 and irradiated for 4-6 h
with visible light (300 W tungsten bulb, slide projector). Air
was then bubbled through the mixture for 20 min, and the
aqueous methanol solution was carefully decanted from the
beads. The aldehyde concentration was determined using
HPLC. This procedure was repeated using new solvent until
negligible amounts of aldehyde were formed. Yield calculations
(Table 1) were based upon the number of AQs in the reactant
polymer. Irradiation of the resin with 350 nm UV light using
a Rayonet Chamber Reactor gave similar results.
Gen er a l P r oced u r e for R eloa d in g of R esin . Polymer
beads resulting from the photolysis of F LP or P LP were placed
in a 50 mL round-bottom flask along with a large excess of
K2CO3, 10 equiv of 1-hydroxy-9,10-anthraquinone for use as
a proton shuttle, and 40 equiv of the desired halide in dry THF.
The reaction was heated to 40-50 °C for ca. 3 days, during
which time the beads became bright red while the solution
turned from red to a faint yellow. The beads were vacuum
filtered and washed with acetone, 50/50 water/methanol, and
methanol, until the washings from the three solvents were
colorless. The beads were then vacuum dried and irradiated
following the general procedure above. The yield was calcu-
lated on the basis of the millimoles of aldehyde produced in
the photolysis of the reloaded resin and the millimoles of
available AQ-OH groups in the resin before reloading. The
latter is equivalent to the millimoles of aldehyde formed in
the previous photolysis.
1-Ben zyloxy-2-(11-ca r boxyu n d ecyl)-9,10-a n th r a qu in o-
n e (9). To a solution of 1.01 g (2.09 mmol) of 8 in 55 mL of
acetone in a 40 °C water bath was added dropwise 1.47 mL of
2.06 M H2CrO4 (3.03 mmol). After 5 min, the reaction mixture
was cooled in an ice bath, diluted with 40 mL of water, and
extracted with ether (3 × 40 mL). The ether layers were
combined and washed with 0.5 M NaOH (2 × 40 mL). The
aqueous layer was acidified with HCl and extracted with
methylene chloride (2 × 45 mL). Removal of the solvent under
reduced pressure in a rotary evaporator gave a yellow solid
that was chromatographed on silica gel and eluted with
methylene chloride-acetone (2:1) to give 0.730 g (70%) of 9.
An analytically pure sample was obtained after several re-
crystallizations from toluene-heptane: mp 144-145 °C; IR
(KBr) 3201, 2917, 2851, 1721, 1674, 1580, 1471, 1326, 1277,
1245, 1048, 979, 730, 710 cm -1; H NMR (250 MHz, CDCl3) δ
8.24-8.35 (m, 2H), 8.10 (d, J ) 7.92 Hz, 1H), 7.75-7.83 (m,
2H), 7.58-7.65 (m, 3H), 7.37-7.49 (m, 3H), 5.06 (s, 2H), 2.72
(t, J ) 7.82 Hz, 2H) 2.34 (t, J ) 7.50 Hz, 2H), 1.53-1.68 (m,
4H), 1.20-1.38 (m, 12H); 13C NMR (250 MHz, CDCl3) δ 183.20,
182.79, 180.06, 157.49, 145.86, 137.23, 135.68, 134.79, 134.12,
133.79, 133.48, 132.68, 128.54, 128.38, 128.18, 127.32, 126.62,
125.93, 123.68, 76.27, 34.09, 30.55, 30.21, 29.58, 29.38 (2), 29.2,
29.05, 24.68. Anal. Calcd. for C32H34O5: C, 77.08; H, 6.87;
Found: C, 77.18; H, 7.07.
1-Ben zyloxy-2-(11-ca r boxyu n d ecyl)-9,10-a n th r a qu in o-
n e, NHS Ester (10). To a 50 mL round-bottom flask were
added 0.720 g (1.44 mmol) of 9, 0.342 g (1.66 mmol) of DCC,
and 0.190 g (1.66 mmol) of NHS in 35 mL of dry THF. The
reaction was monitored by TLC (silica gel, 9:1 CH2Cl2-MeOH).
After ca. 25 h, the reaction mixture was cooled in an ice bath
and vacuum filtered to remove the insoluble urea. Removal of
the solvent from the mother liquor under reduced pressure in
a rotary evaporator gave a solid residue that was chromato-
graphed on silica gel and eluted with methylene chloride-
acetone (20:1) to yield 0.675 g (79%) of 10 as a yellow solid.
Recrystallization from toluene-hexane gave an analytically
pure sample: mp 99-100 °C; IR (KBr) 2924, 2853, 1813, 1785,
1744, 1673, 1325, 1309, 1296, 1253, 1248, 1210, 1075, 726, 714
1
cm-1; H NMR (250 MHz, CDCl3) δ 8.22-8.33 (m, 2H), 8.08
(d, J ) 7.92 Hz, 1H), 7.70-7.82 (m, 2H), 7.62 (d, J ) 7.92 Hz,
3H), 7.34-7.48 (m, 3H), 5.06 (s, 2H), 2.82 (s, 4H), 2.71 (t, J )
7.82 Hz, 2H) 2.60 (t, J ) 7.50 Hz, 2H), 1.50-1.68 (m, 4H),
1.20-1.44 (m, 12H); 13C NMR (250 MHz, CDCl3) δ 183.00,
182.63, 169.32, 168.68, 157.41, 145.75, 137.28, 135.63, 134.82,
134.07, 133.73, 133.44, 132.62, 128.52, 128.34, 128.15, 127.24,
126.52, 125.87, 123.60, 76.13, 30.90, 30.47, 30.18, 29.56, 29.38,
29.30, 29.28, 29.03, 28.72, 25.59, 24.56. Anal. Calcd for C36H37
-
NO7: C, 72.59; H, 6.26; N, 2.35; Found: C, 72.51; H, 6.12; N,
2.23.
Ack n ow led gm en t. We are grateful to Professor
Greg Baker of Michigan State University for allowing
us to take advantage of his polymer expertise. We also
gratefully acknowledge the donors of the Petroleum
Research Fund, administered by the American Chemi-
cal Society, for financial support of this research. R.P.S.
thanks the Camille and Henry Dreyfus Foundation for
financial support. R.L.B. thanks Calvin College for a
Calvin Research Fellowship.
3-(4-Nitr op h en yl)p r op a n a l (13). To a solution of 0.170 g
(0.940 mmol) of 3-(4-nitrophenyl)-1-propanol in 15 mL of CH2-
Cl2 was added 0.304 g (1.41 mmol) of pyridinium chlorochro-
mate. The reaction mixture was heated to reflux for 1.5 h,
cooled, and combined with 35 mL of ether. After the solids were
removed by gravity filtration, the solvents in the filtrate were
evaporated under reduced pressure in a rotary evaporator. The
crude product was chromatographed on silica gel and eluted
with CH2Cl2 giving 0.111 g (66.1%) of analytically pure 13:
IR (film) 3068, 2944, 2900, 2830, 2728, 1723, 1610, 1577, 1525,
1
1452, 1394 cm-1; H NMR (250 MHz, CDCl3) δ 9.75 (s, 1H),
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and spectral data for 1-bromo-3-(4-nitrophenyl)pro-
pane, 1-iodo-3-(4-nitrophenyl)propane, and 3-(4-nitrophenyl)-
1-propanol. This material is available free of charge via the
Internet at http://pubs.acs.org.
8.04 (d, J ) 8.54 Hz, 2H), 7.29 (d, J ) 8.55 Hz, 2H), 2.97 (t, J
) 7.33 Hz, 2H), 2.79 (t, J ) 7.33 Hz, 2H); 13C NMR (250 MHz,
CDCl3) δ 200.36, 148.44, 146.50, 129.27, 123.72, 44.42, 27.75;
MS (EI) m/e (rel intensity) 179 (40), 137 (32), 91 (35), 86 (65),
84 (100). Anal. Calcd for C9H9NO3: C, 60.33; H, 5.06; N, 7.82.
Found: C, 59.99; H, 5.27; N, 7.69.
J O025508U