Simple and general synthesis of new 11H-11λ5-dibenzo[c,f][1,2,5]dithiaphosphepine derivatives

Treatment at room temperature of benzothiadiphosphole 1 with bis-Grignard 2 gives intermediate A, which after 3 h gives intermediate A′. Subsequent addition of RMgX or sodium alcoholate and final treatment with S8 and water affords the title compounds 5 in good yields. From the reaction mixture it is also possible to obtain the cyclic phosphine sulfide 6 or its dimeric form 7.