99-100° C.) have been isolated as solids. Its shelf-life at ambient temperature is only 6 months, Borane complexes of pyridine, 2-n-propylpyridine, 3-methylpyridine, 3-ethylpyridine and 4-ethylpyridine are liquids which violently decompose upon distillation (Mooney E. to avoid decomposition via hydroboration/polymerization processes. Unfortunately, it is thermally unstable and must be kept at temperatures less than 54° C. Pyridine borane is commercially available and often used in acetic acid to increase the reactivity of the borane.
Pyridine forms an amine borane that is not moisture sensitive and very useful for reductive aminations and reductions in protic media. Moreover, such complexing agents are sometimes difficult to remove from the reaction mixture and isolation of the desired product may become laborious. Numerous borane complexes with aliphatic and aromatic amines are known, but their reactivity is frequently not sufficient to reduce a specific functional group. For example, sulfide boranes are highly concentrated but their commercial use is limited because of their strong odor. 6,048,985, the storage stability of borane-THF complex in THF solution is increased significantly at low temperatures, even for solutions with higher concentrations.īorane reagents with other complexing agents are available but suffer from inherent disadvantages. However, the borane-THF complex is prone to thermal decomposition by ether cleavage of the tetrahydrofuran ring, leading to butoxyboranes and ultimately to tributylborate as decomposition products. The most used source of borane is a tetrahydrofuran (THF) solution of the borane-THF complex, which is commercially available, usually with a concentration of 1 mol/l. Functional groups reduced by such borane complexes include aldehyde, ketone, lactone, epoxide, ester, amide, oxime, imine and nitrile groups. In order to reduce the hazards of diborane, complexes of borane (BH 3) with donor molecules like ethers, sulfides, amines and phosphines are invariably used for organic reactions, especially for the reduction of functional groups and for hydroboration reactions with alkenes and alkynes. It must be handled with utmost precautions and must be shipped and stored at temperatures below −20° C. BACKGROUND OF THE INVENTIONĭiborane (B 2H 6) is a toxic and pyrophoric gas that is very readily hydrolysed and oxidised.
The present invention relates to new borane complexes with substituted pyridines, a process for the synthesis of new borane complexes with substituted pyridines, solutions comprising new borane complexes with substituted pyridines and a method of using new borane complexes with substituted pyridines for organic reactions. Provisional application 60/846,144, filed Sep. This application is a national stage application (under 35 U.S.C.
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