Weak Bases‐Mediated Modified Favorskii Reaction‐Type Direct Alkynylation/(E)‐Alkenylation: A Unified Rapid Access to α,β‐Unsaturated Ketones and Propargyl Alcohols

Abstract Herein, we report an unprecedented, fast, highly efficient, transition‐metal‐free, modified Favorskii reaction‐type direct alkynylation and ( E )‐alkenylation protocol towards the synthesis of α , β ‐unsaturated ketones and propargyl alcohols that proceeds using the combination of Cs 2 CO 3 and Et 3 N as weak bases in up to 99% yields. In this reaction, aromatic aldehydes afforded α,β‐unsaturated ketones and aliphatic aldehydes furnished propargyl alcohols, respectively. A proposed mechanistic pathway illustrates the involvement of weak base‐assisted propargylation of carbonyl compounds followed by allenol‐enone tautomerism to furnish ( E )‐alkenylated product.