Carbonazidic acid, 1,1-dimethylethyl ester

Preparationtert-Butyl chloroformate was prepared in solution as follows. Dry phosgene was introduced into a solution of 18 g (0.24 mol) of tert-butyl alcohol in 500 ml of anhydrous ether until about 52 g (0.5 mol) had been absorbed and the mixture was cooled in a Dry Ice-acetone bath. Then a solution of 20 g (0.28 mol) of pyridine in 200 ml of anhydrous ether was added dropwise with vigorous stirring. The reaction mixture was stored overnight in a Dry Ice box. The precipitated pyridine hydrochloride was filtered and the volume of the filtrate was reduced to -70 ml at reduced pressure with cooling in an icewater bath.This cold solution of tert-butyl chloroformate was added over 30 min to a vigorously stirred solution of 31.6 g (0.2 mol) of tetramethylguanidinium azide in 200 ml of chloroform; the temperature was kept at 0°C throughout the addition. The bath was removed and the reaction mixture stirred for an additional hour and then poured into 500 nil of ice water containing -2 ml of acetic acid. Extraction with two 60-ml portions of ether followed by careful evaporation of the dried (magnesium sulfate) organic phase gave tert-butyl azidoformate as a pale amber liquid in quantitative yield.The Direct Preparation of tert-Butyl Azidoformate