Organic Syntheses Procedure

Org. Synth. , 61, 14

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DOI: 10./orgsyn.061.

OXIDATION OF 5-AMINOTETRAZOLES:

BENZYL ISOCYANIDE

[

Benzene, isocyanomethyl

]

Checked by Orville L. Chapman and Thomas C. Hess.

1. Procedure

Caution! This preparation should be conducted in an

efficient hood

due to the unpleasant odor of isocyanide.

5-Benzylaminotetrazole

. Add freshly distilled

benzaldehyde

(21.2 g, 0.2 mol)

to a warm (50°C) solution of

5-aminotetrazole

(17.2 g, 0.2 mol)

(Note 1)

and

triethylamine

(20.2 g, 0.2 mol)

in

100 mL of absolute

methanol

. After 15 minutes, cool the reaction mixture to room temperature, transfer to an

autoclave

, and hydrogenate with stirring at room temperature over

Pd

(10%) on

carbon

(1 g) for 18 hours at 500 psi (pounds per square inch) of

hydrogen

. Remove the catalyst by filtration and evaporate all volatile materials at 60°C under aspirator pressure. Triturate the resulting gummy tan solid with 250 mL of hot water. Add aqueous

20%

HCl

until pH 3 is reached. Cool the mixture to room temperature, collect the solid, wash with water, and dry overnight at room temperature under reduced pressure (100 µ); yield:

27.5 g

(

80%

); mp

183.5–185°C

(lit. mp

183°C

).

B.

Benzyl isocyanide

. In a

500-mL round-bottomed flask

with a

magnetic stirring bar

and a

pressure-equalizing funnel

, place

5-benzylaminotetrazole

(10.5 g, 60 mmol)

,

100 mL of 10%

sodium hydroxide

solution, and

70 mL of

dichloromethane

. Cool the mixture to 0°C and add a solution of

NaOBr

in water (165 mL, 65 mmol)

(Note 2)

with vigorous stirring over 15 minutes

(Note 3)

. Separate the

dichloromethane

layer and extract the aqueous phase with five

50-mL portions of

dichloromethane

. Dry the combined

dichloromethane

extracts over anhydrous

MgSO4

, remove the drying agent by filtration, and distill off the

dichloromethane

. Reduce pressure to approximately 20 mm with an aspirator and distill

benzyl isocyanide

at

98–100°C

; yield:

5.91 g

(

84%

).

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