title: Catalytic conversion of γ-valerolactone to ε-caprolactam: towards nylon from renewable feedstock.
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.
authors.affiliation: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands), Fax: (+31) 71-527-4451.
authors.forename: Saeed
authors.initials: S
authors.lastname: Raoufmoghaddam
authors.forename: Marcus T M
authors.initials: MT
authors.lastname: Rood
authors.forename: Florine K W
authors.initials: FK
authors.lastname: Buijze
authors.forename: Eite
authors.initials: E
authors.lastname: Drent
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bouwman
mesh_terms: D002209:Caprolactam / Q000737:chemistry*; D002384:Catalysis; D003247:Conservation of Natural Resources; D007783:Lactones / Q000737:chemistry*; D009757:Nylons / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D007783:Lactones; D009757:Nylons; D014867:Water; D002209:Caprolactam; C037556:gamma-valerolactone
keywords: biomass; caprolactam; hydroamidomethylation; levulinic acid; reductive amidation