By the formal extension of the Passerini reaction to thiocarbonyl derivatives, the straightforward preparation of thiophthalides is disclosed. This method involves the intermediate formation of a sulfanyl-phthalide and a titanium tetrachloride mediated isocyanide insertion reaction. When tert-butyl thiol is used, thanks to the deprotection of the tert-butyl group, a thiophthalide resulting from a 1,5-Mumm rearrangement is isolated. Owing to the multifaceted activity of TiCl4, all steps may conveniently be performed in one pot, starting directly from 2-formylbenzoic acids, tert-butyl thiol, and various isocyanides.
The Ugi reaction has drawn considerable attention over the years leading to numerous libraries of heterocycles and various extensions changing the nature of the components of the coupling. We report here the use of nitric acid as carboxylic acids surrogates, displaying the first aminative Ugi-type reaction leading to nitramines.
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