vendredi 29 juin 2007

Synthesis of benzothiazole

Yes, I am still alive, but lot of work, so not time to post something this last weeks...

Of course I have missed a lot of things, but I will start the most recent chemistry.

In looking the e-first of Synthesis, I discover the one-pot synthesis of benzothiazoles starting from o-haloanilide with a tandem thionation with the Lawesson's reagent and an intramolecular cyclization, the authors propose as mechanism an intramolecular nucleophilic substitution, for me that sounds weird because the best results are obtained with both fluoro and iodio thioanilide, I would propose the formation of radical anion on sulfur or something like this which could be consistent with the results, nonetheless, this is a very interesting transformation.


One-Pot Preparation of 2-(Alkyl)arylbenzothiazoles from the Corresponding o-Halobenzanilides, Dan Bernardi, Lalla Aïcha Ba, Gilbert Kirsch, Synthesis, 2007, e-first.


That reaction reminds me a 2006 JOC have read some months ago, talking about, of course, the synthesis of benzothiazoles starting from simple thioanilides and using Dess-Martin periodinane to promote the cyclization in only 15minutes in DCM. And in their case they propose a radical intramolecular cyclization!!!










15 commentaires:

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Thomas a dit…

The oxidative cyclization has been known for decades. Potassium Ferricyanide works well in the place of the Dess-Martin reagent.

joebear a dit…

I don't think that the radical formation conditions do exist here.A benzynic intermediate would also be possible followed by a thiophilic addition.

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