Ethyl chloroformate, photolysis

The standard preparation of 2-oxazolidinones is by treatment of /3-amino alcohols with phosgene or its synthetic equivalents ethyl chloroformate, dialkyl carbonates or even urea (equation 174). Isocyanates react with oxiranes in the presence of amines to yield 2-oxazolidinones (equation 175) (79LA200). The action of isocyanates on cyclic carbonates results in 2-oxazolidinones (equation 176) and photolysis of alkyl azidoformates affords oxazolidinones via intermediate nitrenes (equation 177). 

A primary step, in which ethoxycarbonyl radicals are produced via the rupture of carbon-chlorine bonds, has been proposed by Pac and Tsutsumi for the continuous photolysis of ethyl chloroformate with a high pressure mercury arc. The pure compound decomposes to give ethyl chloride with smaller amounts of acetaldehyde, ethane, ethylene, hydrogen chloride, carbon monoxide and carbon dioxide. 

The conversion of berberines into spirobenzylisoquinolines has been examined in detail. As described in section 8 photolysis of the betaines (190, R=H) and (190, R=Me) affords the aziridines (198, R=H) and (198, R=Me). Treatment of (198, R= Me) with methyl iodide is accompanied by Hofmann degradation to give the ochotensine analogue (307, R=Me) and treatment with ethyl chloroformate results in a von Braun degredation... 

An interesting smooth ring opening of o-diazides to form 1,4-dicyanobutadiene has been discovered A selective cleavage of the Ci-N-bond of certain isoquinoline derivatives can be effectively performed with ethyl chloroformate. This little known cleavage was discovered approximately 40 years ago and used recently again with success Photolysis of solutions of 1,2,3-triazolines results in loss of nitrogen and clean formation of aziridines... 

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