The synthesis method of new 3,4-positioned fused tricyclic indole derivatives or benzofuran compounds, and the provision of a new pharmaceutical composition. The method is exemplified by the preparation of 6a from the compound represented by 5a as shown below. The synthesis method includes the steps of contacting 5a with a catalyst containing platinum in a solvent to form a π-allyl platinum intermediate via Friedel-Crafts reaction, and as a second step, reacting the π-allyl platinum intermediate with a base in an intramolecular allylic amination reaction or intramolecular allylic oxidation reaction to close the ring and obtain 6a.【Selected drawing】Figure 1
A novel platinum‐catalyzed cascade cyclization reaction was developed by intramolecular Friedel–Crafts‐type C−H coupling of aniline derivatives with a propargyl carbonate unit‐allylic amination sequence. Treatment of various propargyl carbonates tethered to meta‐aniline derivatives with a Pt(dba)3/DPEphos catalyst system afforded the corresponding 3,4‐fused tricyclic 3‐alkylidene indolines in 42–99 %