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4 BCl 3 + 3 LiAlH 4 → 2 B 2 H 6 + 3 LiAlCl 4 4 BF 3 + 3 NaBH 4 → 2 B 2 H 6 + 3 NaBF 4. When heated with NaBH 4, tin(II) chloride is reduced to elemental tin, forming diborane in the process: SnCl 2 + 2NaBH 4 → 2NaCl + Sn + B 2 H 6 + H 2. Older methods entail the direct reaction of borohydride salts with a non-oxidizing acid, such as ...
Ketene cycloadditions proceed by a concerted, [2+2] cycloaddition mechanism. Ketenes, unlike most alkenes, can align antarafacially with respect to other alkenes. Thus, the suprafacial- antarafacial geometry required for concerted, thermal [2+2] cycloaddition can be achieved in reactions of ketenes. [4]
Without an additive, the reaction product is 2,3-dihydrofuran (2,3-DHF) and not the expected 2,5-dihydrofuran (2,5-DHF) together with the formation of ethylene gas. Radical scavengers, such as TEMPO or phenol , do not suppress isomerization ; however, additives such as 1,4-benzoquinone or acetic acid successfully prevent unwanted isomerization .
The reaction is named after its co-discoverer, John E. McMurry. The McMurry reaction originally involved the use of a mixture TiCl 3 and LiAlH 4, which produces the active reagents. Related species have been developed involving the combination of TiCl 3 or TiCl 4 with various other reducing agents, including potassium, zinc, and magnesium.
The copper-catalyzed version of this reaction gives only the 1,4-isomer, whereas Huisgen's non-catalyzed 1,3-dipolar cycloaddition gives both the 1,4- and 1,5-isomers, is slow, and requires a temperature of 100 degrees Celsius. [15] The two-copper mechanism of the CuAAC catalytic cycle
[2] The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols [ 3 ] (e.g. valinol ). It adds across alkenes to give organoboron compounds that are useful intermediates. [ 4 ]
The Bamford–Stevens reaction is a chemical reaction whereby treatment of tosylhydrazones with strong base gives alkenes. [ 1 ] [ 2 ] [ 3 ] It is named for the British chemist William Randall Bamford and the Scottish chemist Thomas Stevens Stevens (1900–2000).
Hydroboration of 1,2-disubstituted alkenes, such as a cis or trans olefin, produces generally a mixture of the two organoboranes of comparable amounts, even if the steric properties of the substituents are very different. For such 1,2-disubstituted olefins, regioselectivity can be observed only when one of the two substituents is a phenyl ring.