This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functionalization for the synthesis of heterocyclic compounds.
An efficient base, additive and metal-free synthetic methods for α-ketothioamide and α-ketoamide derivatives from readily available sulfoxonium ylides have been described. Sulfoxonium ylides with primary or secondary amines afforded α-ketothioamides in the presence of elemental sulfur, whereas α-ketoamides were produced when I 2 and TBHP were present. The reaction proceeded well at room temperature and generated the corresponding molecules in good to excellent yields. The reaction can be scaled-up and tolerated by a range of functional groups with simple operational procedures.
Here we report a metal-free iodine/tert-butyl hydroperoxide mediated reaction of N-substituted indoles with dimethylformamide (DMF) / dimethylacetamide (DMA). The reaction produces bis-and tris(indolyl)methanes (BIMs and TIMs), in which DMF/DMA provides the methylene (of BIMs) and methine carbons (of TIMs). We have established different optimized conditions for their synthesis. Iodine (10 mol %) with TBHP (in decane, 1.0 equivalent) in DMF/DMA at 130 8C is required for the BIMs synthesis, whereas iodine (20 mol %) with TBHP (in water, 3.0 equivalent) in DMF-H 2 O or DMA-H 2 O (9:1) is needed for the TIMs. This methodology could be used to synthesize a variety of BIMs and TIMs. We believe, this is the first report of their metal-free synthesis through CÀH functionalization using one carbon source. The use of inexpensive, metal-free and environmentally benign catalyst made the method handy.[a] Dr.
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