sir can you pls provide me with complete mechanism of this reaction

Dear student,

Hydrazone iodination  in which a hydrazone is converted into a vinyl chloride by reaction of iodine and a non-nucleophilic base such as DBU  . 

The reaction has earlier roots with the 1911 discovery by Wieland and Roseeu that the reaction of hydrazones with iodine alone (without base) results in the azine dimer (structure 2 in scheme 1).

In the original Barton publication the reaction was optimized by using a strong quanidine base, the inverse addition of the hydrazone to an iodine solution, and by exclusion of water.