How can I have a concerted addition of bromines?

I know how to add Bromines in the antiperiplanar position, but I have no idea how to get concerted addition:


[![](https://i.stack.imgur.com/R7QUN.png)](https://i.stack.imgur.com/R7QUN.png)


Perhaps I am not seeing something obvious, but I would greatly appreciate any hint.




The proper term for *concerted addition* is *syn addition*. I can't find any way of a direct way of producing a syn-addition product. The only way I can figure you would have to do it is if you did the halogenation with water as the solvent you would get the halo-hydrin product with an anti-addition. You could then follow this up with a bromination using $\ce{P,Br2}$ or $\ce{PBr3}$ which would invert the chirality and give you a syn-product.


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