Synthesis and ¹H, ¹³C and ³¹P NMR studies of 2,10‐dichloro‐6‐aryloxy‐12H‐dibenzo [d,g] [1,3,2]‐dioxaphosphocin 6‐oxides

The spectral analyses and syntheses of several novel 2,10‐dichloro‐6‐aryloxy/alkyl‐12 H ‐dibenzo [ d , g ] [1,3,2] dioxaphosphocin 6‐oxides have been achieved. Long‐range coupling [ 5 J (H,P) = 2.4 Hz] was observed between phosphorus and the bridged methylene protons. Based upon NMR data, a tub‐like conformation is proposed for the central eight‐membered dioxaphosphocin ring. Long‐range 2 J (P,O,C) and 3 J (P,O,C,C) couplins were determined, as were the 31 P chemical shifts for sixteen members of these new heterocycles. A variable‐temperature study of one member suggested the presence of a tub form as a reasonable candidate for one major conformer but the presence of other forms was also implied.