Regiospecific formal [3 + 2] annulation of tert-propargyl alcohols with acyclic 1,3-diketones via the cycloisomerization of homoallenyl ketones

Abstract

A one-pot, regiospecific synthesis of dihydrofurans bearing a quaternary centre and tetrasubstituted furans is developed from the formal [3 + 2] annulation of tert-propargyl alcohols and 1,3-diketones under Ca(II)/DBU conditions. The reaction proceeds through the S_N2^I mechanism to form homoallenyl ketone and a subsequent cycloisomerization to yield novel and new chemical entities of privileged scaffolds.