The utilization of the photoredox catalyst, tris(2,2'-bipyridyl)ruthenium dichloride, and a household light bulb to effect radical cyclizations onto indoles and pyrroles at room temperature is reported. A reactive free radical intermediate is generated via the reduction of an activated C-Br bond by the single electron reductant, Ru(I), generated in a visible light induced photocatalytic cycle. This system represents an expansion of the application of photoredox catalysis in conventional free radical processes.

Herein, we report an advancement in the application of visible light photoredox catalysts in a classic free radical mediated reaction, cyclization onto unactivated pi-systems. The reactive radical intermediate is generated by the single electron reduction of an activated C-Br bond by an electron-rich redox catalyst afforded by a visible light induced catalytic cycle.

8388 5.3. Formation of acetals catalyzed by bismuth(III) triflate 8388 5.4. Formation of 1,l-diacetates (acylals) 8389 5.5. Cleavage of epoxides catalyzed by bismuth(III) chloride 8389 5.6. Glycosylation promoted by bismuth(III) chloride 8389 5.7. Selective hydrolysis of aryl esters using bismuth(III) mandelate 5.8. Carbon-sulfur bond formation 5.8.1. Synthesis of thioacetals 8389 5.8.2. Conversion of epoxides to thiiranes 8390 5.9. Sulfonylation of aromatics 8390 5.10. Synthesis of sulfides and selenides promoted by Sm-BiCI3 8391 5.11. Synthesis of allyl sulfides 8391 5. 12. Formation of carbon-halogen bonds 8391 5.12.1. Synthesis of �-haloketones and esters 8391 5.12.2. Chlorination of alcohols catalyzed by bismuth(III) salts 8391 5.12.3. Synthesis of peracetylated glycosyl halides 8392 6. Reductions with bismuth compounds 8392 6.1. Selective reduction of nitro compounds to azoxy compounds 8392 6.2. Reduction of nitro compounds to amines 8392 6.3. Chemoselective reduction of a,�-unsaturated ethyl esters using BiCI3-NaBH 4 8392 6.4. Reduction of aromatic a-haloketones 8393 6.5. Miscellaneous reductions 8393 7. Rearrangements promoted by bismuth(III) salts 8393 7.1. Rearrangement of epoxides 8393 7.2. Allylic rearrangement of glycols (the Ferrier rearrangement) 8394 8. Conclusions

Aerobic hydroperoxidation of Meldrum’s acid derivatives via a Cu(II)-catalyzed process is presented. The mild reaction conditions are tolerant to pendant unsaturation allowing the formation of endoperoxides via electrophilic activation. Cleavage of the O–O bond provides 1,n-diols with differentiation of the hydroxy groups.

An iridium-catalyzed method was developed for the synthesis of imidazo-fused pyrrolopyrazines. The presence or absence of a nitrogenated ligand controlled the outcome of the reaction, leading to simple β-keto amine products in the absence of added ligand and the cyclized 7- and 8-substituted-imidazo[1,2-a]pyrrolo[2,3-e]pyrazine products in the presence of ligand. This catalyst control was conserved across a variety of ylide and amine coupling partners. The substrate was shown to act as a ligand for the iridium catalyst in the absence of other ligands via NMR spectroscopy. Kinetic studies indicated that formation of the Ir-carbene was reversible and the slow step of the reaction. These mechanistic investigations suggest that the β-keto amine products form via an intramolecular carbene N-H insertion, and the imidazopyrrolopyrazines form via an intermolecular carbene N-H insertion.