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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]
Also called "banana borane", it exists as a dimer. It can be distilled without decomposition at 195 °C (12mm Hg). Reactions with 9-BBN typically occur at 60–80 °C, with most alkenes reacting within one hour. Tetrasubstituted alkenes add 9-BBN at elevated temperature. Hydroboration of alkenes with 9-BBN proceeds with excellent regioselectivity.
Effects of additives on the ratio of 2,3- and 2,5-DHF obtained by ring closing metathesis reaction of dially ether. Another common problem associated with RCM is the risk of catalyst degradation due to the high dilution required for some cyclizations.
[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]
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.
The less hindered faces of the enone and alkene react. [9] Intramolecular enone–alkene cycloaddition may give either "bent" or "straight" products depending on the reaction regioselectivity. When the tether between the enone and alkene is two atoms long, bent products predominate due to the rapid formation of five-membered rings. [10]
[2] 1,2-disubstituted Cycloalkene undergoing syn and anti addition. Syn addition is the addition of two substituents to the same side (or face) of a double bond or triple bond, resulting in a decrease in bond order but an increase in number of substituents. [3] Generally the substrate will be an alkene or alkyne.