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AlCl3 and Md compounds

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I have been thinking along the same lines, as I'm currently doing a little light reading on substituted cathinone analogues. Since propionyl chloride/AlCl3 + 1,3-benzodioxole will not work, I was wondering whether whether propionyl chloride/AlCl3 will affect hydroxies, such as from catechol, which can then have the methylenedioxy bridge added as the next step.

If you choose a milder lewis acid, such as TiCl4 instead of AlCl3, you will experience a lot less ether breakage problems.

The problem isn't just the MD-bridge may be torn off, it most certainly won't be torn off cleanly either in a friedel-crafts alkylation, so instead of just collecting the debris after the reaction and reattach any MD bridge, you will have all sorts of breakdown products (a.k.a. tar), which cannot be fixed. Better never break it in the first place.

Is TiCl4 a strong enough Lewis base to remove the chloride from an acid chloride, without greatly affecting yields? Being a weaker base, yields may be affected. Does anyone have a reference to compare Friedal-Crafts acylations with AlCl3 to those with TiCl4?

Here is an example with TiCl4, the yields are only moderate, mostly because friedel-crafts alkylations with nitroalkenes is not optimal - it is fantastic that the reaction worked that good at all!

Since AlCl3 and 1,3-benzodioxole doesn't work I've tried TiCl4 and 1,3-benzodioxole in DCM with EtCOCl (external water/ice cooling). After several seconds a violent boilover produced so much gaseous CH2Cl2 that my dropping funnel (with pressure equalization !) was blown away. It seems that the "milder" lewis acid TiCl4 isn't the right choice for acylations of 1,3-benzodioxole.


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