Construction of Thiochroman-4-ols through a (4 + 2) Annulation Strategy Using Allenyl Sulfones as Substrates

Herein, we report an efficient and straightforward access to highly functionalized thiochroman-4-ol derivatives by the construction of S-C and C-C bonds in a domino fashion. The methodology is based on a (4 + 2) annulation reaction involving α-substituted allenyl sulfones and aromatic thiolates displaying an ortho α-ketoester group as substrates. The anionic sulfur species were generated in situ by reduction of the corresponding disulfides, using a Rongalite/K2CO3 system. The practicality of the strategy was further demonstrated by gram-scale synthesis, postmodifications, and compatibility with other types of electron-deficient allenes (allenoate and allenone).