Triphosgene: an efficient chlorination reagent for synthesis of 5-chloro-2-pentanone from 3-acetyl-1-propanol
5-Chloro-2-pentanone (5C2P) and its derivatives are widely utilized in the pharmaceutical and agrochemical industry. A new catalytic approach was proposed to convert 3-acetyl-1-propanol to 5C2P using bis(trichloromethyl)carbonate (triphosgene, BTC) as the efficient chlorine source. Various qualitative and quantitative nuclear magnetic resonance techniques ( 1 H, 13 C NMR), especially 1D selective gradient total correlation spectroscopy (Sel-TOCSY) and 2D heteronuclear single quantum correlation ( 1 H- 13 C HSQC) were used in the process. The reaction conditions, such as temperature, time, mole ratio, solvent as well as initiator were optimized. Experiment results showed that the yield of 5C2P reached a maximum of 97.93% in 1,2-dichloroethane at 80 °C after 2 h under the initiation of N,N-dimethylacetamide, and the optimal molar ratio of 3-acetyl-1-propanol to BTC was 1:0.4. The reaction mechanism was proposed and confirmed accordingly. Interestingly, an intermediate product of 1-(dimethylamino)ethyl carbonochloridate was observed, and its chemical structure was characterized by both Sel-TOCSY and 1 H- 13 C HSQC. This study enriched the catalytic reaction ways for the preparation of 5C2P.
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