We performed the one-pot preparation of bupropion in class where the bromination of the carbon adjacent to the carbonyl group was performed using DCM as solvent, and upon completion the solvent was switched to n-methyl-2-pyrrolidone and was then reacted with an amine. I know that the nucleophilic substitution won't occur in DCM, the reason for which was also explained here on this site, so what alternate solvent could be used that allow for both bromination and substitution to occur without a solvent switch, AND still allow this procedure to still be conducted within a single class session? I asked the professor, but he said that he would have to think about it and get back to me... yeah, I have a feeling I am being blown off.
I believe that water would work for the bromination as long as the mixture is kept acidic, but then that complicates things with the amine as it will need to be in its basic form, unless that doesn't matter because by the time you add the amine, the bromination has already taken place and you would just neutralize first. However, aren't these reactions very slow in aqueous conditions? I know that water lowers nucleophilicity, so would that explain the hindered reaction times?
What about acetonitrile? I know this can be used in bromination, as I have read procedures that claim increased selectivity for monobromination.
In the event that you are not familiar with the preparation I am referring to, I am providing a link to the ACS paper that we used as the basis of the experiment. http://pubs.acs.org/doi/abs/10.1021/ed077p1479
EDIT: There is also a follow up question regarding the usage of more than an equivalent of the amine during the substitution step as an acid scavenger. What is up with that? Why isn't the acid being formed in the substitution step being neutralized with an appropriate base that won't hydrolyze the bromoketone first? This just seem rudimentary to me, but I lack the encompassing understanding at this time. Is there a procedure I could reference as an example of what I just proposed?