Promote The Carbonylation Reactions Of Alkyl Halides Under Mild Conditions. Light

Recently photopromoted hydroesterification of olefins with carbon monoxide under room temperature and normal pressure arises people's interests, which is also an important method to prepare methyl ester. There are few researches on the photopromoted hydroesterification of relatively low cost halides. In this paper, using a series of different types of halides as substrates, non-precious metal cobalt salts as catalyst, methyl esters are selectively obtained.The halides used as substrate include benzyl chloride, chloroacetic acid ethyl ester, bromocyclohexane, iodobutane(n-), bromobutane(n-), chlorobutane (n-),bromopentane(n-), etc. Given the appropriate conditions, they can be photopromoted carbonylized under room temperature and normal pressure, with esters as products. The influences of various factors are investigated, cobalt salts are good catalysts, sodium acetate is effective additive, whose ability of promotion is much better than that of other additives. Certain amount of sodium acetate added, the yield and selectivity of the reaction can increase significantly.Using carbon dioxide instead of carbon monoxide and increasing irradiation time,the same reactions and results are obtained,with disadvantages that the yield and selectivity of esters are not satisfying compared with the carbonylation of carbon monoxide. Due to the chemical inactivity of carbon dioxide and the environmental problems it caused, the carbonylation using carbon dioxide becomes an important topic with potentiality and a new area of green chemistry.The mechanism of carbonylation of benzyl chloride with carbon dioxideis investigated by ESR (Electron Spin Resonance),finding that carbon dioxide after irradiation changes to CO2 radicals, therefore a mechanism is derived under the guidance of experimental results and references.