phosphite it undergoes intramolecular cyclization leading to diphospholane VI. In this case, the high temperature of the process and removal of butyl chloride from the reaction sphere favor cyclization. Similar formation of stable five-membered rings,(1, 2-oxaphospholanes) was previously observed on attempted preparation of (3-halopropyl) phosphonates [3, 4] and also while using them as alkylating agents in polar media [4].
![[dibutoxyphosphorylmethyl(phenyl)phosphoryl]benzene Structure](https://image.chemsrc.com/caspic/130/17045-53-3.png)