Advertisement

Springer Nature is making Coronavirus research free. View research | View latest news | Sign up for updates

Towards a Phosgene-Free Synthesis of Aryl Isocyanates: Alcoholysis of N-phenylurea to N-phenyl-O-methyl Carbamate Promoted by Basic Metal Oxide Nanoparticles and Organocatalysts

  • 747 Accesses

  • 22 Citations

Abstract

There is an urgent need to develop new processes for the synthesis of polyurethanes and polycarbonates different from the current technology based on the use of phosgene. In the case of polyurethanes, the reaction of phosgene with aromatic amines renders N-aryl isocyanates that are the co-monomers for these polymers. In the search for a phosgene-free process for the synthesis of N-aryl isocyanates, N-aryl carbamates could play a key role of synthetic precursors. N-Aryl carbamates can be prepared in turn by alcoholysis of N-aryl ureas. Herein, we compare the catalytic activity of three homogeneous catalysts and four heterogeneous metal oxides for the methanolysis of N-phenylurea as a model probe for other aromatic ureas. In the present work we have carried out this reaction in the presence of KOH, 1,8-diaminonaphthalene (a protonic sponge), a dimeric phosphazene (strong, neutral soluble base) and nanometric ZnO, MgO, CaO and a mixed Mg/Al metal oxide derived from hydrotalcite calcination. Besides the target N-phenyl O-methyl carbamate, N-phenyl isocyanate and undesired aniline were also formed. It was observed that using KOH and diaminonaphthalene, aniline was formed preferentially with respect to the desired carbamate. In contrast, dimeric phosphazene forms the target N-phenyl O-methyl carbamate with 90% selectivity at 99% N-phenylurea conversion. In the case of the metal oxides, the best-performing solid catalyst was CaO that exhibits similar activity (99% N-phenylurea conversion) and carbamate selectivity (89%) as phosphazene. CaO performs as a truly heterogeneous catalyst and could be reused for a second run with only a 4 and 2% decrease in conversion and selectivity, respectively.

This is a preview of subscription content, log in to check access.

Scheme 1
Scheme 2
Scheme 3
Scheme 4
Fig. 1
Scheme 5

References

  1. 1.

    Weissermel K, Harpe H-J (2003) Industrial organic chemistry. Wiley-VCH, Weinheim

  2. 2.

    Kirk (1994) Othmer encyclopedia of chemical technology. John Wiley, New York

  3. 3.

    Smirnova NA, Zhdaneeva GS, Vaisman VD (1971) Case of phosgene inhalation poisoning complicated by subcutaneous emphysema. Gig Tr Prof Zabol 15:46–48

  4. 4.

    Bashirov AA, Glikshtein MD (1969) Clinical aspects of acute combined poisoning due to chlorine and phosgene. Gig Tr Prof Zabol 13:49–50

  5. 5.

    Soko, Lowski F (1952) Phosgene as soluble cutaneous allergen. Przegl Dermatol 2:411–418

  6. 6.

    Streda L, Cisarova V (1998) Controls on the import and export of goods and technology with multiple uses in order to meet the requirements of the treaty on the banning of chemical weapons. Chem Prum 73:18–20

  7. 7.

    Murray LE (1997) The chemical weapons convention and its impact on us industry––an overview. Book of abstracts, 213th ACS national meeting, San Francisco, April 13–17

  8. 8.

    Poliakoff M, Fitzpatrick JM, Farren TR, Anastas PT (2002) Green chemistry: science and politics of change. Science 297:807–810

  9. 9.

    Anastas PT, Kirchhoff MM (2002) Origins, current status, and future challenges of green chemistry. Acc Chem Res 35:686–694

  10. 10.

    March J (1993) Advanced organic chemistry: reactions, mechanisms and structures. McGraw Hill, New York

  11. 11.

    Tundo P, Selva M (2002) The chemistry of dimethyl carbonate. Acc Chem Res 35:706–716

  12. 12.

    Aresta M, Dibenedetto A (2007) Utilisation of CO2 as a chemical feedstock: opportunities and challenges. Dalton Trans 2975–2992

  13. 13.

    Aresta M (2003) Utilization of greenhouse gases, pp 2–39

  14. 14.

    Distaso M, Quaranta E (2008) Sc(OTf)3-catalyzed carbomethoxylation of aliphatic amines with dimethyl carbonate (DMC): DMC activation by Π· 1-O(C=O) coordination to Sc(III) and its relevance to catalysis. J Catal 253:278–288

  15. 15.

    Querci C, Cesti P, Panella F, Ricci M (2003) Process for the preparation of aromatic urethanes by carbamoylation of organic carbonates with aromatic amines, using complexes of lanthanides or Group III metals as catalysts. Eni SpA, Italy; Enichem SpA, Iraly, p 21

  16. 16.

    Srivastava R, Srinivas D, Ratnasamy P (2005) Zeolite-based organic-inorganic hybrid catalysts for phosgene-free and solvent-free synthesis of cyclic carbonates and carbamates at mild conditions utilizing CO2. Appl Catal A 289:128–134

  17. 17.

    Aresta M, Dibenedetto A (2002) Mixed anhydrides: key intermediates in carbamates forming processes of industrial interest. Chem Eur J 8:685–690

  18. 18.

    Carloni S, De Vos DE, Jacobs PA, Maggi R, Sartori G, Sartorio R (2002) Catalytic Activity of MCM-41-TBD in the selective preparation of carbamates and unsymmetrical alkyl carbonates from diethyl carbonate. J Catal 205:199–204

  19. 19.

    Hacking MAPJ, van Rantwijk F, Sheldon RA (2000) Lipase catalyzed reactions of aliphatic and arylaliphatic carbonic acid esters. J Mol Catal B 9:201–208

  20. 20.

    Smith RC, Hunns JCB (1998) Process for the production of organic isocyanates by the reaction of amines with organic carbonates to form carbamate esters which undergo thermal decomposition to the isocyanates, PCT Int Appl WO 9856758. Imperial Chemical Industries, UK, p 13

  21. 21.

    Smith RC (1998) Method and catalysts for the preparation of carbamates from amines and organic carbonates, PCT Int Appl WO 9855451. Imperial Chemical Industries, UK, p 11

  22. 22.

    Smith RC (1998) Process and catalysts for the preparation of N-arylcarbamates by the amidation of organic carbonate esters with arylamines, PCT Int Appl WO 9855450. Imperial Chemical Industries, UK, p 15

  23. 23.

    Bosetti A, Cesti P, Calderazzo F (1997) Process and catalysts for the production of aromatic carbamates from aromatic amines and alkyl carbonates, Eur Pat Appl EP 752413. Ministero Dell’ Universita’ E Della Ricerca Scientifica E Tecnologica, Italy, p 9

  24. 24.

    Aresta M, Berioco C, Quaranta E (1995) Biomimetic building-up of the carbamic moiety: the intermediacy of carboxyphosphate analogs in the synthesis of N-aryl carbamate esters from arylamines and organic carbonates promoted by phosphorus acids. Tetrahedron 51:8073–8078

  25. 25.

    Chankeshwara SV (2008) Dimethyl carbonate (DMC): a versatile and environmentally benign building block. Synlett 624–25

  26. 26.

    Selva M (2007) Green approaches to highly selective processes: reactions of dimethyl carbonate over both zeolites and base catalysts. Pure Appl Chem 79:1855–1867

  27. 27.

    Tundo P, Selva M (2007) Dimethyl carbonate as a green reagent. Met Reag Green Chem 77–102

  28. 28.

    Ouk S, Thiebaud S, Borredon E, Chabaud B (2005) N-Methylation of nitrogen-containing heterocycles with dimethyl carbonate. Synth Commun 35:3021–3026

  29. 29.

    Tundo P (2004) Dimethyl carbonate as a green reagent. Chim Oggi 22:31–34

  30. 30.

    Tundo P, Perosa A (2002) Green organic syntheses: organic carbonates as methylating agents. Chem Rec 2:13–23

  31. 31.

    Jiang X, Tiwari A, Thompson M, Chen Z, Cleary TP, Lee TBK (2001) A practical method for n-methylation of indoles using dimethyl carbonate. Org Process Res Dev 5:604–608

  32. 32.

    Tundo P (2001) New developments in dimethyl carbonate chemistry. Pure Appl Chem 73:1117–1124

  33. 33.

    Memoli S, Selva M, Tundo P (2001) Dimethylcarbonate for eco-friendly methylation reactions. Chemosphere 43:115–121

  34. 34.

    Tundo P (2000) Selective monomethylation reactions of methylene-active compounds with dimethyl carbonate. An example of clean synthesis. Pure Appl Chem 72:1793–1797

  35. 35.

    Juarez R, Padilla A, Corma A, Garcia H (2008) Organocatalysts for the reaction of dimethyl carbonate with 2,4-diaminotoluene. Ind Eng Chem Res ACS ASAP

  36. 36.

    Riley D, McGhee WD, Waldman T (1994) Generation of urethanes and isocyanates from amines and carbon dioxide. ACS Symp Ser 577:122–132

  37. 37.

    Vairo G, Guidetti G, Pignagnoli F (2002) Polyurethane formulations. Chim Ind (Milan, Italy) 84:43–48

  38. 38.

    Buist JM, Lowe A (1971) Organic isocyanates and their utilization in the production of polymeric materials. Brit Polym J 3:104–119

  39. 39.

    Aresta M, Dibenedetto A, Devita C, Bourova OA, Chupakhin ON (2004) New catalysts for the conversion of urea into carbamates and carbonates with C1 and C2 alcohols. Stud Surf Sci Catal 153:213–220

  40. 40.

    Wu C, Zhao X, Wang Y (2005) Effect of reduction treatment on catalytic performance of Zn-based catalyst for the alcoholysis of urea to dimethyl carbonate. Catal Commun 6:694–698

  41. 41.

    Aresta M, Dibenedetto A, Pastore C (2004) An integrated approach to the synthesis of organic carbonates: discovery of new catalysts. Prepr Symp Am Chem Soc Div Fuel Chem 49:356–357

  42. 42.

    Climent MJ, Corma A, Iborra S, Epping K, Velty A (2004) Increasing the basicity and catalytic activity of hydrotalcites by different synthesis procedures. J Catal 225:316–326

  43. 43.

    Corma A, Iborra S, Miquel S, Primo J (1998) Catalysts for the production of fine chemicals. Production of food emulsifiers, monoglycerides, by glycerolysis of fats with solid base catalysts. J Catal 173:315–321

  44. 44.

    Corma A, Garcia H, Primo A (2006) Palladium and copper supported on mixed oxides derived from hydrotalcite as reusable solid catalysts for the Sonogashira coupling. J Catal 241:123–131

  45. 45.

    Hattori H (1995) Heterogeneous basic catalysis. Chem Rev 95:537–558

  46. 46.

    Sels BF, De Vos DE, Jacobs PA (2001) Hydrotalcite-like anionic clays in catalytic organic reactions. Catal Rev Sci Eng 43:443–488

  47. 47.

    Tanabe K, Holderich WF (1999) Industrial application of solid acid-base catalysts. Appl Catal A 181:399–434

  48. 48.

    Enders D, Niemeier O, Henseler A (2007) Organocatalysis by N-heterocyclic, carbenes. Chem Rev 107:5606–5655

  49. 49.

    Marion N, Diez-Gonzalez S, Nolan IP (2007) N-heterocyclic carbenes as organocatalysts. Angew Chem Int Ed 46:2988–3000

  50. 50.

    Pratt RC, Lohmeijer BGG, Long DA, Waymouth RM, Hedrick JL (2006) Triazabicyclodecene: a simple bifunctional organocatalyst for acyl transfer and ring-opening polymerization of cyclic esters. J Am Chem Soc 128:4556–4557

  51. 51.

    Enders D, Grondal C, Huttl MRM (2007) Asymmetric organocatalytic domino reactions. Angew Chem Int Ed 46:1570–1581

  52. 52.

    Chen XH, Luo SW, Tang Z, Cun LF, Mi AQ, Jiang YZ, Gong LZ (2007) Organocatalyzed highly enantioselective direct aldol reactions of aldehydes with hydroxyacetone and fluoroacetone in aqueous media: the use of water to control regioselectivity. Chem Eur J 13:689–701

  53. 53.

    Alder RW, Bowman PS, Steele WRS, Winterman DR (1968) The remarkable basicity of 1,8-bis(dimethylamino)naphthalene. Chem Commun 723–725

  54. 54.

    Angelaud R, Landais Y (1997) Tetrahedron Lett 38:8841–8845

  55. 55.

    Gao J, Li H, Zhang Y, Zhang Y (2006) Green Chem 9

  56. 56.

    Dai Y, Wang Y, Yao J, Qingyin G, Liu L, Chu W, Wang G (2008) Catal Lett 123:307–316

  57. 57.

    Wang X-K, Yan S-r, Li Z-H, Fan K, Kang M-Q, Peng S-Y (2004) Kor J Chem Eng 21:378–380

  58. 58.

    Tundo P, Selva M, Memoli S (2000) Dimethylcarbonate as a green reagent. ACS Symp Ser 767:87–99

Download references

Acknowledgments

Financial support by the Spanish DGI (MAT 2006-14274-CO2-01 and CTQ06-6859) is gratefully acknowledged. R.J. thanks the Spanish Ministry of Science and Education for a post-graduate scholarship.

Author information

Correspondence to Hermenegildo García.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Juárez, R., Corma, A. & García, H. Towards a Phosgene-Free Synthesis of Aryl Isocyanates: Alcoholysis of N-phenylurea to N-phenyl-O-methyl Carbamate Promoted by Basic Metal Oxide Nanoparticles and Organocatalysts. Top Catal 52, 1688–1695 (2009). https://doi.org/10.1007/s11244-009-9303-4

Download citation

Keywords

  • Green chemistry
  • Organocatalysis
  • Metal oxides as catalysts
  • Phosgene replacement