Efficient Piancatelli rearrangement on a large scale using the Zippertex technology under subcritical water conditions†
Piancatelli rearrangement of furyl carbinols is a relevant reaction to produce cyclopentenone derivatives. However, on a large scale, Piancatelli rearrangement suffers from several serious drawbacks such as long reaction periods, high dilution conditions, moderate yields, and the formation of dark brown polymeric materials. We describe here the first use of Zippertex, an innovative technology that reaches subcritical water conditions (100–150 °C and 100 bars). Under these conditions, this rearrangement proceeds smoothly to provide clean crude reaction mixtures without the formation of side-products and dark brown polymeric materials. Thus, a series of simple furyl carbinols directly obtained from bio-sourced furfural and more challenging non-symmetrical furan-2,5-dicarbinol substrates, also obtained from a bio-sourced raw material (HMF), were efficiently transformed into cyclopentenone derivatives in good yields. This technology could be applied successfully on challenging substrates substituted by an aliphatic group and also performed on a 500 mmol scale.