Green Chemistry, Pages: Ahead of Print
M. Drop, X. Bantreil, K. Grychowska, G.U. Mahoro, E. Colacino, M. Pawlowski, J. Martinez, G. Subra, P. Zajdel, F. Lamaty
2,5-Dihydro-1H-pyrrole-3-carboxylates are important building blocks for the synthesis of high value pyrroles and pyrroloquinoline derivs. with interesting biol. activities. The use of continuous flow allowed us to perform a key synthetic step, namely ruthenium-catalyzed ring-closing metathesis, with a residence time of 1 min at 120 °C. Di-Me carbonate, a green solvent, was demonstrated for the first time to be an excellent solvent for this reaction in continuous flow. The continuous flow conditions proved to be general and the scale-up of this reaction was not only possible, but also highly efficient. Conversion of 10 g of diene was realized in 37 min under continuous flow, yielding the desired heterocycle in 91% yield.