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The conversion provides a useful approach for remote functionalization in long-chain alkynes. [2] The reaction requires a strong base. The base used by Brown and Yamashita was potassium 1,3-diaminopropanide, generated in situ by adding potassium hydride to the solvent 1,3-diaminopropane. [1]
Additionally, LiOH fails to form the necessary adduct with alkynes to initiate the reaction. Hydroxide bases are inexpensive relative to generating an alkoxide or acetylide with reagents such as elemental lithium, sodium, or potassium. Additionally, the stringent reaction conditions used by most alternatives, such as excluding moisture and ...
Alkyne metathesis is an organic reaction that entails the redistribution of alkyne chemical bonds. The reaction requires metal catalysts. The reaction requires metal catalysts. Mechanistic studies show that the conversion proceeds via the intermediacy of metal alkylidyne complexes .
Diimide reductions result in the syn addition of dihydrogen to alkenes and alkynes. This observation has led to the proposal that the mechanism involves concerted hydrogen transfer from cis-diimide to the substrate. The cis isomer is the less stable of the two; however, acid catalysis may speed up equilibration of the trans and cis isomers. [5] (2)
Metal alkyne complexes are intermediates in the semihydrogenation of alkynes to alkenes: C 2 R 2 + H 2 → cis-C 2 R 2 H 2. This transformation is conducted on a large scale in refineries, which unintentionally produce acetylene during the production of ethylene. It is also useful in the preparation of fine chemicals. Semihydrogenation affords ...
[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.
[4] [5] Hydrogenation occurs with syn stereochemistry when used on an alkyne resulting in a cis-alkene. Some of the most important transformations include the hydrogenation of ketones to alcohols or ethers (the latter product forming in the presence of alcohols and acids) [ 6 ] and the reduction of nitro compounds to amines. [ 7 ]
The second part of the reaction converts the isolable gem-dibromoalkene intermediate to the alkyne. Deuterium-labelling studies show that this step proceeds through a carbene mechanism. Lithium-Bromide exchange is followed by α-elimination to afford the carbene. 1,2-shift then affords the deuterium-labelled terminal alkyne. [ 3 ]
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