Construction Of Bisindole-Annulated Thiopyran Based On Isatin-Derived Morita-Baylis-Hillman Carbonates

The indole ring system is an important structural motif,which is common in natural products,drugs and other synthetic compounds.Among many indole derivatives,indole-annulated heterocycle compounds including sulfur atoms are often found as structural unit of bioactive natural compounds and drugs.Recently,new synthetic methods for constructing structurally novel indole-annulated sulfur heterocycles have been explored constantly.Although several synthetic methods have been developed to these indole compounds,there are relatively few examples of synthesis indole-annulated thiopyran compounds in the known literature.Recently,our research group reported an efficient Lewis base catalyzed diastereoselective [3+3] spiroannulation process,which can produce indole-based sulfides.It has been shown to undergo Michael addition/[3+3] spiroannulations to produce bisindole-annulated thiopyran compounds.In this paper,a novel highly diastereoselective tandem Michael addition/[3+3] spiroannulation reaction between isatins derived Morita-Baylis-Hillman(MBH)carbonates and indoline-2-thiones is described.The reaction was catalyzed by a single DMAP to obtain a variety of bisindole-annulated thiopyran derivatives with complex structures in good yields with good diastereoselectivities.This simple method was a powerful tool for the construction of bisindole-annulated thiopyran derivatives with diastereoselectivity.These derivatives had C-N/C-S bonds,and the unique structure could be considerable interest for potential drug discovery.In addition,this method provided a valuable approach for the synthesis of these potentially bioactive scaffolds,which would be suitable for generation of relevant natural products synthesis libraries,and would be widely used in organic synthesis and pharmaceutical chemistry.