Triphosgene Explained

Triphosgene (bis(trichloromethyl) carbonate (BTC) is a chemical compound with the formula OC(OCCl₃)₂. It is used as a solid substitute for phosgene, which is a gas and diphosgene, which is a liquid.^{[1] [2]} Triphosgene is stable up to 200 °C. Triphosgene is used in a variety of halogenation reactions.

Preparation

This compound is commercially available. It is prepared by exhaustive free radical chlorination of dimethyl carbonate:^[2]

CH₃OCO₂CH₃ + 6 Cl₂ → CCl₃OCO₂CCl₃ + 6 HClTriphosgene can be easily recrystallized from hot hexanes.

Uses

Triphosgene is used as a reagent in organic synthesis as a source of CO²⁺. It behaves like phosgene, to which it cracks thermally:

Alcohols are converted to carbonates. Primary and secondary amines are converted to ureas and isocyanates.^{[2] [3] [4] [5]}

Triphosgene has been used to synthesize chlorides.^[6] Some Alkyl chlorides are prepared by treating alcohols with a mixture of triphosgene and pyridine. Alkyl dichlorides and trichlorides can similarly be synthesized using triphosgene. Vinyl chlorides are synthesized from ketones using triphosgene and DMF to form a Vilsmeier reagent, followed by a ring opening by chloride ions. Aryl chlorides can also be produced using a Vilsmeier reagent from triphosgene and DMF.

Safety

The vapor pressure of Triphosgene is sufficiently high for it to reach concentrations that are considered toxicologically unsafe.^[7] While several properties of triphosgene are not yet readily available, it is known that it is very toxic if inhaled. A toxic gas is emitted if it comes in contact with water.^[8] There is a lack of information and variability regarding the proper handling of triphosgene. It is assumed to have the same risks as phosgene.^{[9] [10]}

See also

• Phosgene
• Diphosgene

External links

• Bulletin about Triphosgene
• Material Safety Data Sheet

Notes and References

1. Book: 10.1002/047084289X.rb200 . Bis(trichloromethyl) Carbonate . Encyclopedia of Reagents for Organic Synthesis . 2001 . Roestamadji . Juliatiek . Mobashery . Shahriar . 0471936235 .
2. Heiner Eckert . Barbara Forster . 1987 . Triphosgene, a Crystalline Phosgene Substitute . Angew. Chem. Int. Ed. Engl. . 26 . 9 . 894–895 . 10.1002/anie.198708941.
3. Akiba T, Tamura O, Terashima S . 10.15227/orgsyn.075.0045 . (4R,5S)-4,5-Diphenyl-3-Vinyl-2-Oxazolidinone . Organic Syntheses . 75 . 45 . 1998 .
4. Tsai JH, Takaoka LR, Powell NA, Nowick JS . 10.15227/orgsyn.078.0220. Synthesis of Amino Acid Ester Isocyanates: Methyl (S)-2-Isocyanato-3-Phenylpropanoate. Organic Syntheses. 78. 220. 2002.
5. Du H, Zhao B, Shi Y . 10.15227/orgsyn.086.0315. Pd(0)-Catalyzed Diamination of Trans-1-Phenyl-1,3-Butadiene with Di-tert-Butyldiaziridinone as Nitrogen Source. Organic Syntheses. 86. 315. 2009. free.
6. Ganiu MO, Nepal B, Van Houten JP, Kartika R . A decade review of triphosgene and its applications in organic reactions . Tetrahedron . 76 . 47 . 131553 . November 2020 . 33883783 . 8054975 . 10.1016/j.tet.2020.131553 .
7. Cotarca L, Geller T, Répási J . 2017-09-15 . Bis(trichloromethyl)carbonate (BTC, Triphosgene): A Safer Alternative to Phosgene? . Organic Process Research & Development . en . 21 . 9 . 1439–1446 . 10.1021/acs.oprd.7b00220 . free .
8. Web site: 2009 . Material Safety Data Sheet: Triphosgene . February 17, 2022 . Acros Organics.
9. Damle SB . Safe handling of diphosgene, triphosgene. . Chemical & Engineering News . February 1993 . 71 . 6 . 4 .
10. Pauluhn J . Phosgene inhalation toxicity: Update on mechanisms and mechanism-based treatment strategies . Toxicology . 450 . 152682 . February 2021 . 33484734 . 10.1016/j.tox.2021.152682 . 231693591 . free .