Acyl Azides from Mixed Acid Chlorides

1 Acyl Azides from Mixed Acid Chlorides 

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It should be mentioned at this stage that instead of acyl chlorides, mixed anhydrides may also be used for the synthesis of acyl azides. From carboxylic acids and chloroformates/triethylamine, mixed anhydrides are formed, which can directly react with azide ions. Sterically hindered acids fail in this procedure (equation 31)." " The similar synthesis of /-butyl azidoformate by reaction of /-butylcarbonic diethylphosphoric anhydride with KN3 is described in Organic Syntheses. ... 

Sample preparation Mix 300 pL of a 30 pM solution in dichloromethane with 10 pL 20 mM l-(6-methoxy-2-naphthyl)ethyl isothiocyanate in anhydrous dichloromethane and 50 pL 0.1% triethylamine in dichloromethane, vortex thoroughly, heat at 50° for 1.5 h, inject an aliquot. (Synthesize l-(6-metho -2-naphthyl)ethyl isothiocyanate as follows (protect from light). Dissolve 500 mg (S)-(+)-naproxen in 50 mL dry toluene, slowly add 5 mL freshly distilled thionyl chloride, reflux for 1 h, evaporate to dryness under vacuum, dry the acyl chloride (mp 87.5°) under vacuum over KOH for 2 days. Dissolve 0.5 mmoles acyl chloride in 5 mL acetone, stir at 0°, add 0.6 mmoles sodium azide dissolved in ice water, stir at 0° for 30 min, add 10 mL ice-cold water, filter, dry solid in a desiccator under vacuum. Dissolve the solid in 1 mL toluene or dichloromethane (dried over 3 A molecular sieve), reflux for 10 min, evaporate, store resulting isocyanate (mp 51°) under vacuum over a desiccant. Dissolve 0.5 mmole isocyanate in 5 mL acetone, add 20 mL 8.5% phosphoric acid, heat to 80° for 1.5 h, adjust to pH 13, extract with diethyl ether dichloromethane 4 1. Wash the organic layer twice with water, dry over anhydrous sodium sulfate, evaporate to dryness, dissolve in 1 mL toluene, evaporate to give the amine from... 

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