740
A. R. Bressette, L. C. Glover IV
LETTER
Methyl 3-Cyclohexyl-2-propenoate 1H NMR (60 MHz, 5% TMS/
CDCl3): d = 6.93 (dd, 1 H), 5.74 (dd, 1 H), 3.71 (s, 3 H), 1.49 (m,
11 H). 13C NMR (14 MHz, 5% TMS/CDCl3): d = 167.20, 154.36,
118.73, 51.21, 40.54, 31.87, 26.09, 25.84.
(Scheme 3). Remarkably, the use of this sterically hin-
dered Wittig reagent gave excellent results, with only
modest reductions in the yield and Z:E ratio. This suggests
that other stabilized Wittig reagents should be compatible
with this new one-pot methodology.
1
Methyl 2-Hexenoate H NMR (60 MHz, 5% TMS/CDCl3): d =
6.95 (dt, 1 H), 5.80 (dt, 1 H), 3.70 (s, 3 H), 2.18 (q, 2 H), 1.50 (h, 2
H), 0.93 (ds, 6 H). 13C NMR (14 MHz, 5% TMS/CDCl3): d =
147.90, 121.35, 96.08, 50.63, 34.07, 21.32, 13.64.
O
(a) PCC, celite, CH2Cl2, 3 h
OH
OC(CH3)3
R
Methyl 2-Octenoate 1H NMR (60 MHz, 5% TMS/CDCl3): d = 6.98
(dt, 1 H), 5.73 (dt, 5 H), 3.65 (s, 3 H), 2.15 (m, 2 H), 1.31 (m, 2 H),
0.90 (m, 7 H). 13C NMR (14 MHz, 5% TMS/CDCl3): d = 165.64,
148.52, 121.35, 50.75, 32.26, 31.56, 28.03, 22.64, 14.06.
Methyl 5-Methyl-2-hexenoate 1H NMR (60 MHz, 5% TMS/
CDCl3): d = 6.95 (dt, 1 H), 5.80 (ds, 1 H), 3.70 (s, 3 H), 2.11 (m, 3
H), 0.92 (ds, 6 H). 13C NMR (14 MHz, 5% TMS/CDCl3): d =
166.87, 148.32, 122.17, 51.19, 35.31, 22.28, 13.87.
(b) (Ph)3P=CHCO2C(CH3)3
R
R
Yield (%)
89
70
73
E,E:E,Z
91:9
90:10
90:10
Ph
CH3CH2CH2
CH3CH2(CH3)CH
Scheme 3
Methyl 4-Methyl-2-hexenoate 1H NMR (60 MHz, 5% TMS/
CDCl3): d = 6.85 (dd, 1 H), 5.76 (ds, 1 H), 3.70 (s, 3 H), 2.22 (m, 1
H), 0.92 (ds, 6 H). 13C NMR (14 MHz, 5% TMS/CDCl3): d =
167.23, 154.61, 119.58, 51.26, 38.30, 28.93, 19.01, 11.58.
In conclusion, we have developed an efficient one-pot
process for the oxidation–olefination of alcohols combin-
ing PCC and stabilized Wittig reagents.
Methyl 2-(E)-,4-(E)-Octadienoate
General Procedure for Tandem Reaction: PCC (1.5 g, 3.5 mmol)
and Celite® (1.5g) were added to a dry 100 mL round bottomed
flask under N2. To this mixture CH2Cl2 (50 mL) was added and
stirred. Benzyl alcohol (0.25 g, 2.3 mmol) was then added dropwise
and the mixture was allowed to stir at r.t. until the reaction was com-
plete, as verified by TLC, (usually 2–3 h). An amount of 15 mL
Et2O was added and the solution was vacuum filtered through a frit-
ted funnel charged with ca. 2 inches of silica gel and then washed
with 100 mL of a hexane/EtOAc solution (9:1). The solution was
transferred to a 250 mL round bottomed flask. To the stirring solu-
tion was added methyl (triphenylphosphoranylidene)-acetate (2.15
g, 6.4 mmol). The solution was heated to reflux for 3 h. The reaction
was cooled and the solvent was removed by rotary evaporation. The
resulting solid was purified by column chromatography.
Starting with 0.25 g of cis-2-hexene-1-ol, the diene was obtained in
a 71% yield. 1H NMR (60 MHz, 5% TMS/CDCl3): d = 7.23 (dd, 1
H), 6.17 (s, 1 H), 5.91 (s, 1 H), 5.65 (s, 1 H), 3.73 (s, 3 H), 2.09 (m,
2 H), 1.39 (m, 2 H), 0.92 (m, 3 H). 13C NMR (14 MHz, 5% TMS/
CDCl3): d = 167.60, 145.42, 144.48, 128.95, 119.30, 51.39, 35.24,
22.17, 13.75.
Starting with 0.25 g of trans-2-hexene-1-ol, the diene was obtained
in a 79% yield. 1H NMR (60 MHz, 5% TMS/CDCl3): d = 7.23 (dd,
1 H), 6.17 (s, 1 H), 5.91 (s, 1 H), 5.65 (s, 1 H), 3.73 (s, 3 H), 2.09
(m, 2 H), 1.39 (m, 2 H), 0.92 (m, 3 H). 13C NMR (14 MHz, 5%
TMS/CDCl3): d = 167.60, 145.42, 144.48, 128.95, 119.30, 51.39,
35.24, 22.17, 13.75.
Acknowledgment
General Procedure for One-pot Reactions: PCC (29.78 g, 138
mmol) and Celite® (30 g) were added to a dry 500 mL round bot-
tomed flask under N2. To this mixture CH2Cl2 (250 mL) was added
and stirred. Benzyl alcohol (10.0 g, 92 mmol) was dissolved in 5 mL
CH2Cl2 and added dropwise to the reaction mixture, which was then
allowed to stir at r.t. until the reaction was complete, as verified by
TLC, (usually 2–3 h). Methyl(triphenylphosphoranylidene)acetate
(52 g, 156 mmol) was then added and the reaction was allowed to
stir at r.t. for 24 h. An amount of 75 mL Et2O was added to the re-
action mixture which was vacuum filtered through a 140 mL fritted
funnel charged with ca. 2 inches of silica gel (2/3 full) and rinsed
with hexane–EtOAc solution (9:1, 100 mL). The solvent was then
removed by rotary evaporation to afford the pure product.
We thank Berry College for financial support of this work and R.
Evan Nix for the synthesis of the t-butyl Wittig Reagent.
References
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1
Methyl 3-Phenyl-2-propenoate. H NMR (60 MHz, 5% TMS/
CDCl3): d = 7.65 (d, 1 H), 7.35 (m, 5 H), 6.40 (d, 1 H), 3.74 (s, 3 H).
13C NMR (14 MHz, 5% TMS/CDCl3): d = 167.72, 144.74, 134.43,
130.22, 128.85, 128.10, 117.88, 51.46.
(7) Patil, V. J.; Mavers, U. Tetrahedron Lett. 1996, 37, 1281.
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(9) Determined by GC.
Synlett 2004, No. 4, 738–740 © Thieme Stuttgart · New York