Regioselective Opening of Epoxides Catalyzed by Sn (IV). A New Method for the Synthesis of Halohydrins?
نویسنده
چکیده
The regioselective opening of epoxides with organotin oxides 1 and 2, in presence of halogenated alcohols was developed, yielding the halohydrin derivatives. Introduction Epoxides are among the most versatile intermediates in organic chemistry due to the particular polarity and strength of their three member ring. Those characteristics make them in a very suitable substrate to the attack or many nucleophilic and electrophilic reagents [1]. The regioselective opening of oxiranes has been the subject of interest for many years, since these heterocyclics are frequently used as starting material for the preparation of natural products and biological active compounds [2]. Many different organotin reagents have been employed to effect the regioand stereoselective cleavage of oxiranes in the presence of nucleophiles affording 1,2-alcoxialcohols, 1,2-aminoalcohols, 1, 2-azidoalcohols, etc [3]. Results and Discussion As a part of our ongoing research work concerning the development of organotin reagents for the opening of epoxides [4], the bis(tributyltin) oxide (1) and bis(chlorodibutyltin) oxide (2) were subjected to act as Lewis acids assisting the opening of epoxides in the presence of halogenated alcohols. When styrene oxide was reacted with t-BuOH and 1, the starting material was recovered unchanged after 5 days, probably due to steric hindrances. However, when the same reaction was carried out using the oxide 2, after 3 days a compound was isolated and identified as the chlorohydrin. In this case, bis(chlorodibutyltin) oxide would act as a Lewis acid and, moreover, as a chloride donor. In view of the result described above, we decided to extend the study using a series of halogenated alcohols as a nucleophiles in the presence of the organotin oxides 1 or 2. These results outlined in Scheme 1, shows the formation of the halohydrin derivatives in very good Molecules 2000, 5 469 yield by the highly regioselective opening of styrene oxide. However, when the same methodology was applied to other monosubstituted epoxides, the results obtained were different. While the oxide 1, showed a low reactivity towards aliphatic oxiranes, the oxide 2 was able to assist the cleavage of those heterocycles by the nucleophilic attack of the alcohol, or by the chloride anion originated from (ClBu2Sn)2O. The unusual formation of the chlorohydrin compounds would be due to the reaction of the nucleophile with the reagent 2, and the subsequent nucleophilic attack of the chloride over the epoxide. In summary, (ClBu2Sn)2O emerge as a new reagent for the regioselective opening of epoxides yielding the chlorohydrin derivatives, in mild and non-hydrolytic conditions. Acknowledgements: I wish to thanks to Dr. O.A.Mascaretti for his interest and to the Agencia Nacional de Promoción Científica y Tecnológica (SECYT) and Universidad Nacional de Rosario for their financial support. References and Notes 1. Smith, G. J. Synthesis 1984, 629. 2. Schanen, V.; Cherrier, M.; Melo, S.; Quirion, J.; Husson, H. P. Synthesis 1996, 833. 3. Hwang, G.; Chung, J.; Lee, W. J. Org. Chem. 1996, 61, 6183. 4. Salomon, C.J.; Laborde, M.A; Gonzalez Sierra, M.; Mascaretti, O.A. Main Group Metal Chemistry 1998, 21, 617. t-BuOH 1
منابع مشابه
Disulfide catalyzed the highly regioselective conversion of epoxides to halohydrins with elemental halogens
The regioselective ring opening of styrene oxide using elemental iodine and bromine in the presence of disulfides as new catalysts was studied. The conductivity titration and UV spectroscopy were used to study the interaction of iodine with these catalysts. The results indicate that disulfide 11 is efficient in polyiodide formation, and can catalyze this reaction in excellent yield and high reg...
متن کاملDisulfide catalyzed the highly regioselective conversion of epoxides to halohydrins with elemental halogens
The regioselective ring opening of styrene oxide using elemental iodine and bromine in the presence of disulfides as new catalysts was studied. The conductivity titration and UV spectroscopy were used to study the interaction of iodine with these catalysts. The results indicate that disulfide 11 is efficient in polyiodide formation, and can catalyze this reaction in excellent yield and high reg...
متن کاملOne-pot synthesis of highly regioselective β-azido alcohols catalyzed by Brønsted acidic ionic liquids
In this protocol, 3-(2-carboxybenzoyl)-1-methyl-1H-imidazol-3-ium chloride [Cbmim]Cl and sulfonic acid functionalized pyridinium chloride [pyridine-SO3H]Cl as a new, reusable, and green Brønsted acidic ionic liquid (BAIL) catalyst were synthesized and successfully used for the one-pot ring opening of epoxide with sodium azide (NaN3) in water at room temperature. Epoxides under ring-opening easi...
متن کاملRegioselective conversion of epoxides to vicinal nitrohydrins catalyzed by silica-bound 3-{2-[poly(ethylene glycol)]ethyl}-substituted 1-methyl-1H-imidazol-3-ium bromide as a green and reusable catalyst under aqueous thermal conditions
An environmentally benign procedure for the synthesis of vicinal nitrohydrins via the regioselective ring opening reaction of epoxides with nitrite anion using silica-bound 3-{2-[poly(ethylene glycol)]ethyl}-substituted 1-methyl-1H-imidazol-3-ium bromide as an effective heterogeneous phase transfer catalyst was described. Short reaction time, high yield of products, simple work-up proc...
متن کاملRegioselective conversion of epoxides to vicinal nitrohydrins catalyzed by silica-bound 3-{2-[poly(ethylene glycol)]ethyl}-substituted 1-methyl-1H-imidazol-3-ium bromide as a green and reusable catalyst under aqueous thermal conditions
An environmentally benign procedure for the synthesis of vicinal nitrohydrins via the regioselective ring opening reaction of epoxides with nitrite anion using silica-bound 3-{2-[poly(ethylene glycol)]ethyl}-substituted 1-methyl-1H-imidazol-3-ium bromide as an effective heterogeneous phase transfer catalyst was described. Short reaction time, high yield of products, simple work-up proc...
متن کاملMagnesium Oxide Nanoparticles for Catalytic Synthesis of 2-Substituted Alcohols from Regioselective Ring Opening of Epoxides in Water
Epoxides undergo regioselective ring opening with various nucleophiles using catalytic amount of nano magnesium oxide and water as solvent under mild reaction conditions. The remarkable features of this method are improved yields, high regioselectivity, and green chemistry agreement.
متن کامل