- Bromolysis and iodolysis of α,β-epoxycarboxylic acids in water catalyzed by indium halides
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The ring opening of α,β-epoxycarboxylic acids by bromide and iodide ions has been efficiently carried out in water in high regio- and stereoselective fashion. The iodolysis of trans-β-monoalkylated epoxycarboxylic acids at pH 4.0 was completely α-regioselective and anti diastereoselective. The InCl3-catalyzed iodolysis of a variety of α,β-epoxycarboxylic acids at pH 1.5 gave the corresponding anti β-iodohydrins in 88-95% yields. The one-pot synthesis of the α- and β-hydroxyhexanoic acids, starting from the corresponding α,β-epoxycarboxylic acid 1a by iodolysis followed by reduction of the resulting iodohydrins 4a and 4b by NaBH4-InCl3 in water, has been performed.
- Amantini,Fringuelli,Pizzo,Vaccaro
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p. 4463 - 4467
(2007/10/03)
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- A New Synthetic Method of Preparing Iodohydrin and Bromohydrin Derivatives through in Situ Generation of Hypohalous Acids from H5IO6 and NaBrO3 in the Presence of NaHSO3
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Hypohydrous acids such as hypoiodous acid (IOH) and hypobromous acid (BrOH) were found to be easily generated from H5IO6 and NaBrO3 in the presence of an appropriate reducing agent such as NaHSO3.Iodohydrin and bromohydrin derivatives were synthesized in good yields from the reaction of a wide variety of organic compounds bearing carbon-carbon double bonds, with H5IO6 or NaBrO3 and NaHSO3.The iodohydroxylation of internal alkenes was achieved with high stereoselectivity to give anti products, although no stereoselectivity was observed in the bromohydroxylation of these alkenes.It was found that allylic alcohols undergo iodohydroxylation in anti-Markovnikov fashion to form iodo diols in good yields.Treatment of alkynes with H5IO6 combined with NaHSO3 afforded the corresponding ketones in fair yields, but the same treatment with NaBrO3 rather than H5IO6 produced the corresponding α,α-dibromo ketones along with small amounts of the dibromoalkenes.
- Masuda, Haruyoshi,Takase, Kiyoshi,Nishio, Masahiro,Hasegawa, Akira,Nishiyama, Yutaka,Ishii, Yasutaka
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p. 5550 - 5555
(2007/10/02)
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- Etude par la Modelisation Moleculaire de la Regioselectivite de l'Ouverture des Acides Glycidiques par les Amines Aliphatiques
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A model for glycidic acids opening reaction by ammonia and amines has been suggested from semi-empiric orbital calculations.It provides a way for evaluating the different interactions between the incoming nucleophile and the oxirane substituents.Steric and coulombic interactions of the carboxylate in staggered conformation (cis substitution) has a major influence to rationalize experimental regioselectivity.
- Grosjean, F.,Huche, M.,Larcheveque, M.,Legendre, J. J.,Petit, Y.
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p. 9325 - 9334
(2007/10/02)
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- Preparation of α-Bromo- and α-Chlorocarboxylic Acids from α-Amino Acids
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Diazotization of α-amino acids in 48:52 (w/w) hydrogen fluoride/pyridine along with excess of potassium halide results in the corresponding α-halocarboxylic acids in good to excellent yields (Table 1 and 2).
- Olah, George A.,Shih, Joseph,Prakash, G. K. Surya
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p. 1028 - 1030
(2007/10/02)
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