Hydrohalogenation Reaction of Substituted 1,2-Allenic Carboxylic Acids, Esters, Amides, Nitriles, and Diphenyl Phosphine Oxides
- 1 January 2001
- journal article
- research article
- Published by Georg Thieme Verlag KG in Synthesis
- Vol. 2001 (05) , 0713-0730
- https://doi.org/10.1055/s-2001-12759
Abstract
The hydrohalogenation reaction of 1,2-allenic carboxylic acids, esters, amides, nitriles, and diphenyl phosphine oxides with HX or MX (X = I, Br, Cl, M = Na, Li) in different solvents, such as HOAc, CF3CO2H, and CF3CO2H-HOAc (1:1) was studied. The reaction is a nucleophilic conjugate addition in nature and provides efficient entries to 3-halo-3-enoic acids, esters, amides, nitriles, and 2-haloallyl diphenyl phosphine oxides. The β,γ- over α,β-selectivity and stereoselectivity depend on the solvent(s) and the temperature applied. In most cases, the Z- and E-isomers can be easily separated by chromatography on silica gel. The subsequent cross-coupling reaction with organometallic reagents and terminal alkynes showed the synthetic potential of these products.Keywords
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