Formation and Rearrangement of Dithioxo- and Diselenoxophosphoranes Carrying Bulky 4-t-Butyl-2,6-bis(methoxyalkyl)phenyl Groups

[4-t-Butyl-2,6-bis(1-methoxy-1-methylethyl)phenyl]phosphine, [4-t-butyl-2,6-bis(2-methoxy-1,1-dimethylethyl)phenyl]phosphine, and [4-t-butyl-2,6-bis(3-methoxy-1,1-dimethylpropyl)phenyl]phosphine were prepared and allowed to react with sulfur or selenium, to give heterocyclic compounds containing phosphorus–oxygen bond, via rearrangement of the methyl moiety of the methoxy group.