Dehalogenations and other reductive cleavages

Recent Literature

Exposure of (functionalized) aryl chlorides to catalytic quantities of nickel-on-charcoal in the presence of stoichiometric amounts of Me₂NH · BH₃/K₂CO₃ in refluxing acetonitrile leads to high yields of the dehalogenated arenes.
B. H. Lipshutz, T. Tomioka, K. Sato, Synlett, 2001, 970-973.

Air- and moisture-stable (NHC)Pd(allyl)Cl complexes have been used in Suzuki-Miyaura cross-coupling, catalytic dehalogenation of aryl halides, and aryl amination. A general system involving (IPr)Pd(allyl)Cl as catalyst and NaO^tBu as base has proven to be highly active for all reactions. Microwave-assisted processes have afforded yields similar to those of the conventionally heated analogous reactions.
O. Navarro, H. Kaur, P. Mahjoor, S. P. Nolan, J. Org. Chem., 2004, 69, 3173-3180.

Nickel-on-graphite is a very inexpensive, heterogeneous catalyst for the chemoselective reduction of aryl tosylates and mesylates. The catalyst can be used under conventional heating conditions or microwave irradiation and is recyclable without loss of activity.
B. H. Lipshutz, B. A. Frieman, T. Butler, V. Kogan, Angew. Chem. Int. Ed., 2006, 45, 800-803.

Treatment of o-bromonitrobenzenes with various vinyl Grignard reagents gives 7-bromoindoles in good yields, using the o-bromine atom to direct the cyclization. A subsequent reduction using a heteroaryl radical methodology gives 7-unsubstituted indoles in nearly quantitative yields.
A. Dobbs, J. Org. Chem., 2001, 66, 638-641.

(Me₃Si)₃SiH was successfully used in various radical-based transformations in water. The system comprising substrate, silane, and initiator (ACCN) mixed in aqueous medium at 100°C worked well for both hydrophilic and hydrophobic substrates. In case of water-soluble water-soluble substrates, an amphiphilic thiol was also needed.
A. Postigo, S. Kopsov, C. Ferreri, C. Chatgilialoglu, Org. Lett., 2007, 9, 5159-5162.

The In(OAc)₃-catalyzed reaction of bromo- and iodoalkanes with PhSiH₃ in THF at 70 C gave dehalogenated alkanes in good to high yields in the presence of Et₃B and air. 2,6-lutidine as additive enabled an efficient reduction of simple and functionalized iodoalkanes in EtOH. GaCl₃ was found to be an effective catalyst for the reduction of haloalkanes with poly(methylhydrosiloxane).
K. Miura, M. Tomita, Y. Yamada, A. Hosomi, J. Org. Chem., 2007, 72, 787-792.

Nanopalladium particles supported on a amphiphilic polystyrene-poly(ethylene glycol) resin catalyzed hydrogenation of olefins and hydrodechlorination of chloroarenes under aqueous conditions.
R. Nakao, H. Rhee, Y. Uozumi, Org. Lett., 2005, 7, 163-165.

The combination of HMPA and SmBr₂ in THF is a powerful reductant that is capable of reducing ketimines and alkyl chlorides at room temperature. The structure of this reductant has not been established.
B. W. Knettle, R. A. Flowers, II, Org. Lett., 2001, 3, 2321-2324.

A stannane, which is simple to prepare, was successfully used in standard radical reactions as replacement of Bu₃SnH and Ph₃SnH. The tin-containing byproducts are removed by mild hydrolysis and extraction with aqueous NaHCO₃. The performance of this new reagent was tested for reactions involving halides, selenides, Barton-McCombie deoxygenation and enyne cyclization.
D. L. J. Clive, J. Wang, J. Org. Chem., 2002, 67, 1192-1198.

Trifluoromethyl arenes were reduced with lithium aluminum hydride to give toluene derivatives in good yields in the presence of 5 mol % of niobium(V) chloride. Stepwise, partial reduction of a bis(trifluoromethyl) arene was also demonstrated.
K. Fuchibe, Y. Ohshima, K. Mitomi, T. Akiyama, Org. Lett., 2007, 9, 1497-1499.

Indium hydride generated from readily available Et₃SiH and InCl₃ offers mild conditions and low toxicity, and is therefore a promising alternative to Bu₃SnH.
N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.

N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.

A mild, convenient, fast, and nonreductive deiodination is reported for ortho-iodo-hydroxylated arenes using pyridine, triethylamine, and N-methylmorpholine in the presence of water. The regioselectivity is discussed.
R. S. Talekar, G. S. Chen, S.-Y. Lai, J.-W. Chern, J. Org. Chem., 2005, 70, 8590-8593.

Zinc-promoted reduction of 2-(bromomethyl)alkenoates derived from Baylis-Hillman adducts gave (E)-2-methylacrylates in good yield and high stereoselectivity. Synthesis of the male ant pheromone (E)-2,4-dimethyl-2-hexenoic acid was performed using this simple methodology.
L. Fernandes, A. J. Bortoluzzi, M. M. Sa, Tetrahedron, 2004, 60, 9983-9989.

The use of SmI₂ in the reductive elimination of 1,2-acetoxy sulfones (Julia-Lythgoe olefination) and the reductive cleavage of vinyl sulfones is reported.
G. E. Keck, K. A. Savin, M. Weglarz, J. Org. Chem., 1995, 60, 3194-3204.