Organic Syntheses, CV 6, 613
Submitted by Ving Lee and Melvin S. Newman
1.
Checked by Gordon F. Hambly and Peter Yates.
1. Procedure
A.
1-(Diazoacetyl)naphthalene. A solution of
30.5 g. (0.160 mole) of 1-naphthoyl chloride (Note
1) and (Note
2) in
50 ml. of dry diethyl ether (Note
3) is added over 30 minutes to a magnetically stirred, ice-cooled solution of
6.72 g. (0.160 mole) of diazomethane [
Org. Synth., Coll. Vol. 2, 165 (1943); (Note
4)] and
16.1 g. (0.160 mole) of dry triethylamine (Note
5) in
900 ml. of dry ether. The mixture is stirred for 3 hours in the cold, and the
triethylamine hydrochloride, removed by filtration, is washed twice with
30–50 ml. portions of dry ether (Note
6). The
ether is removed from the combined filtrate and washings on a
rotary evaporator. The yellow solid residue is dissolved in
75 ml. of dry ether, and the solution is cooled with an acetone–dry-ice mixture. The solid deposited is collected by filtration on a
glass fritted-disk funnel, and the adhering
ether is removed under reduced pressure as the temperature is allowed to reach room temperature, giving
26.6–28.8 g. (
85–92%) of yellow
1-(diazoacetyl)naphthalene, m.p.
52–53° (Note
7) and (Note
8).
B.
Ethyl 1-naphthylacetate. A solution of
15.7 g. (0.0801 mole) of 1-(diazoacetyl)naphthalene in
50 ml. of absolute ethanol is placed in a
100-ml., two-necked flask equipped with a
Teflon-coated magnetic stirring bar, a
serum stopper cap, and a
reflux condenser connected to a
gas-collecting device. The solution is heated to reflux, and 1 ml. of a freshly prepared catalyst solution made by dissolving
1 g. of silver benzoate (Note
9) in
10 ml. of triethylamine is added by injection through the serum cap. Evolution of
nitrogen occurs and the mixture turns black. Addition of a second milliliter of catalyst solution is made when the evolution of
nitrogen almost stops. This procedure is continued until further additions cause no further evolution of
nitrogen (Note
10). The reaction mixture is refluxed for 1 hour, cooled, and filtered. The solvents are removed from the filtrate on a
rotary evaporator. The residue is taken up in
75 ml. of ether, and the solution is washed twice in turn with aqueous
10% sodium carbonate, water, and saturated
brine. Each aqueous extract is extracted with
ether, and the combined ethereal extracts and solution are dried by filtration through anhydrous
magnesium sulfate. After removal of the
ether, distillation affords
14.4–15.8 g. (
84–92%) of colorless
ethyl 1-naphthylacetate, b.p.
100–105° (0.1–0.2 mm.) (Note
11).
2. Notes
7. This compound is a severe skin irritant; hence, great care should be exercised to avoid any contact. For best yields this crystallization is recommended, since the yield of
ethyl 1-naphthylacetate is reduced by about 20% if the crude product is used in the rearrangement step. A sample of crystallized
1-(diazoacetyl) naphthalene, m.p.
52–53°, that had been stored in a screw-top bottle in a refrigerator for about 2 weeks afforded the same yield of
ethyl 1-naphthylacetate as a freshly prepared sample.
10. Usually 3–4 additions are required. The total time of reaction should not be more than 45 minutes. The checkers added the catalyst solution in 0.5-ml. portions;
nitrogen evolution was initially very vigorous, and only four such additions were required.
3. Discussion
The method described here represents a modified Arndt-Eistert reaction as developed by Newman and Beal,
4 gives results that are more reproducible than those of the original Arndt-Eistert reaction and, in general, allows the rearrangement to be carried out successfully on larger-scale runs. The use of
triethylamine in the formation of diazo ketones makes possible the use of only one equivalent of
diazomethane.
5
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