Substitution of aryl bromide in synthesis of a chelator

Hello I am currently working on a synthesis of a chelator for the synthesis of a photosensitizer for photodynamic therapy. My instructor wants me to do following synthesis procedure:


[![enter image description here](https://i.stack.imgur.com/fFeEQ.png)](https://i.stack.imgur.com/fFeEQ.png)


My problem is, the conditions for the last step are not yet known. How can ipso-substitution of the bromide be carried out? One version we tried was a copper-catalyzed process (CuI (1 eq), DMEDA (0.2 eq, cat.), NaN3 (2 eq.)) which only worked in 10% yield (fragment could only be seen in ESI).


How can the last reaction be sucessfully done?




Protect your phenols (silyl ethers should be OK). Do a metal-halogen exchange with nBuLi or iPrMgCl to make the aryllithium or Grignard and react this with tosyl azide. Work up with sodium pyrophosphate as described in this JACS [paper](https://pubs.acs.org/doi/10.1021/jo01263a047)


Also see this Angewandte [paper](https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201912419) for a recent example which has useful references


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