Continuous niobium phosphate catalysed Skraup reaction for quinoline synthesis from solketalElectronic supplementary information (ESI) available.CCDC 1517275. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6gc03140d

Solketal is derived from the reaction of acetone with glycerol, a by-product of the biodiesel industry. We report here the continuous reaction of solketal with anilines over a solid acid niobium phosphate (NbP), for the continuous generation of quinolines in the well-established Skraup reaction. This study shows that NbP can catalyse all the stages of this multistep reaction at 250 °C and 10 MPa pressure, with a selectivity for quinoline of up to 60%. We found that the catalyst eventually deactivates, most probably via a combination of coking and reduction processes but nevertheless we show the promise of this approach. We demonstrate here the application of our approach to synthesize both mono- and bis-quinolines from the commodity chemical, 4,4′-methylenedianiline. Solketal is derived from the reaction of acetone with glycerol, a by-product of the biodiesel industry. We demonstrate the use of NbOPO 4 as a catalyst for the conversion of solketal and anilines to quinolines.