Catalytic Conversion of γ-Valerolactone to ε-Caprolactam: Towards Nylon from Renewable Feedstock

Authors

  • Saeed Raoufmoghaddam,

    1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451
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  • Marcus T. M. Rood,

    1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451
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  • Florine K. W. Buijze,

    1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451
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  • Prof. Dr. Eite Drent,

    1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451
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  • Prof. Dr. Elisabeth Bouwman

    Corresponding author
    1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451
    • Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451===

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Abstract

The conversion of γ-valerolactone (GVL) in three atom-efficient steps to the important polymer precursor ε-caprolactam is reported. The bio-based GVL can be converted to a mixture of isomeric methyl pentenoates (MP) via trans-esterification with methanol with 94 % yield (ratio of 3-MP/4-MP=3:1); subsequent aminolysis with ammonia leads to a mixture of pentenamides (PA) almost quantitatively (99 % conversion). The resulting pentenamides are ultimately converted into ε-caprolactam via a rhodium-catalyzed intramolecular hydroamidomethylation reaction, comprising an initial hydroformylation of the alkene moiety of PA and subsequent ring-closing reductive amidation of the resulting aldehyde with the amide functionality. A promising yield of caprolactam of about 90 % can be obtained with a Rh/xantphos catalyst system in a two-stage hydroformylation–reductive amidation using pure 4-PA as feedstock. The use of 3-PA as a substrate not only results in a significantly lower regioselectivity for the 7-membered lactam, but also in the formation of high amounts of valeramide (VA). Consequently, a best overall yield of caprolactam of nearly 40 % could be demonstrated with a Rh/POP-xantphos [POP-xantphos=4,5-bis(2,8-dimethyl-10-phenoxaphosphino)-9,9,-dimethylxanthene] catalyst system based on the 3:1 mixture of 3-PA/4-PA directly obtainable from GVL.

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