Categories: C=C Bond Formation >
Reductive alkene formations
Electrolysis using an undivided cell fitted with a pair of zinc electrodes in a mixture of saturated aqueous NH4Br and tetrahydrofuran enables an efficient synthesis of alkenes from epoxides. The reaction is mediated by Zn(0) with a hierarchically organized nanostructure.
J.-M. Huang, Z.-Q. Lin, D.-S. Chen, Org. Lett., 2012, 14, 22-25.
The combination of Re2O7 as catalyst and triphenyl phosphite as a reductant enables the deoxygenation of unactivated aliphatic epoxides to alkenes. The reaction proceeds stereospecifically with variously substituted epoxides under neutral conditions and tolerates various functional groups.
T. Nakagiri, M. Murai, K. Takai, Org. Lett., 2015, 17, 3346-3349.
A highly stereoselective synthesis of aromatic α,β-unsaturated amides was achieved by treatment of aromatic α,β-epoxyamides with samarium diiodide. α,β-epoxyamides are easily prepared by the reaction of enolates derived from α-chloroamides with carbonyl compounds at -78°C.
J. M. Concellón, E. Bardales, J. Org. Chem., 2003, 5, 9492-9295.
The ionic liquid 1-methyl-3-pentylimidazolium fluoroborate, [pmIm]BF4, is an efficient catalyst as well as solvent for the stereoselective debromination of various vicinal-dibromides to the corresponding (E)-alkenes in high yields under microwave irradiation. This reaction does not require any conventional reducing agent, and the ionic liquid can be recycled.
B. C. Ranu, R. Jana, J. Org. Chem., 2005, 70, 8621-8624.
Dichloroindium hydride (Cl2InH) generated in situ from the combination of a catalytic amount of indium(III) chloride and sodium borohydride in acetonitrile reduces activated vic-dibromides to the corresponding (E)-alkenes in excellent yields.
B. C. Ranu, A. Das, A. Hajira, Synthesis, 2003, 1012-1014.
Dimethyl sulfoxide efficiently causes the reductive elimination of 3-aryl 2,3-dibromopropanoates to cinnamates with good yield. For most substrates debromination is the major pathway, whereas dehydrobromination is a competing pathway with thiophene derivatives. 1H NMR, 81Br NMR, and MS indicated the formation of brominated-DMSO, MeBr, and HBr as byproducts.
W. Li, J. Li, M. Lin, S. Wacharasindhu, K. Tabei, T. S. Mansour, J. Org. Chem., 2007, 72, 6016-6021.
An easily accessible copper(I)/N-heterocyclic carbene (NHC) complex enables a regioselective allylic reduction of allylic bromides with (TMSO)2Si(Me)H as hydride source. The reaction provides aryl- and alkyl-substituted branched α-olefins in good yields, which are valuable building blocks for synthesis.
T. N. T. Nguyen, N. O. Thiel, F. Pape, J. F. Teichert, Org. Lett., 2016, 18, 2455-2458.
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.
Stereoselective β-elimination of diastereomeric mixtures of 2-bromo-3-hydroxyesters is achieved by using unactivated manganese and trimethylsilyl chloride, to yield (E)-α,β-unsaturated esters with total diastereoselectivity.
J. M. Concellón, H. Rodríguez-Solla, V. del Amo, Synlett, 2006, 315-317.
Samarium diiodide promotes a photoinduced metalation of nonactivated C-Cl bonds of O-acetyl chlorohydrins and a β-elimination which affords alkenes with total or high stereoselectivity.
J. M. Concellon, H. Rodriguez-Solla, C. Simal, M. Huerta, Org. Lett., 2005, 7, 5833-5835.