Halogen oxides, allylic

It has been demonstrated that fluorovinylzinc reagents undergo stereoselective palladium-catalyzed coupling reactions with aryl (e.g., formation of 2 " ), vinyl (e.g., formation of heteroaryl, alkanoyl. and alkoxycarbonyl halides. Fluorovinylzinc reagents also undergo allyl-ation (e.g., formation of 4 ), halogenation, oxidative dimerization, and protonation reactions. ... 

The amide N-H may also be halogenated, oxidized and nitrosated. A -Bromosuccinimide (NBS), like a number of other iV-halo compounds, readily undergoes a radical fission to give a bromine radical. This provides a useful reagent for radical bromination at, for example, allylic or benzylic positions. In the presence of acid, NBS is also a mild source of the halonium ion, which is used for the addition of hypobromous acid (Scheme 3.74) to alkenes or for the bromination of reactive aromatic rings. 

An allylic halogen oxide [2,3]-sigmatropic rearrangement is another intriguing analogue of the Mislow-Evans process. In this scenario tScheme 1R.7QT oxidation of an allylic iodide provides iodoso intermediate 282, which rearranges to the corresponding allylic hypoiodite 283. Yamamoto et al. found that the reaction worked best with excess peracid oxidant, as the initially formed hypoiodite was further oxidized to the iodate ester (284), an intermediate... 

Generally, isolated olefinic bonds will not escape attack by these reagents. However, in certain cases where the rate of hydroxyl oxidation is relatively fast, as with allylic alcohols, an isolated double bond will survive. Thepresence of other nucleophilic centers in the molecule, such as primary and secondary amines, sulfides, enol ethers and activated aromatic systems, will generate undesirable side reactions, but aldehydes, esters, ethers, ketals and acetals are generally stable under neutral or basic conditions. Halogenation of the product ketone can become but is not always a problem when base is not included in the reaction mixture. The generated acid can promote formation of an enol which in turn may compete favorably with the alcohol for the oxidant. 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

Naphthalene dioxygenase from P. putida strain FI is able to oxidize a number of haloge-nated ethenes, propenes, and butenes, and d5 -hept-2-ene and cis-oct-2-ene (Lange and Wackett 1997). Alkenes with halogen and methyl substituents at double bonds form allyl alcohols, whereas those with only alkyl or chloromethyl groups form diols. 

---