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Usually two equivalents of sodium amide yields the desired alkyne. Three equivalents are necessary in the preparation of a terminal alkynes because the terminal CH of the resulting alkyne protonates an equivalent amount of base. Hydrogen chloride and ethanol can also be eliminated in this way, [11] as in the preparation of 1-ethoxy-1-butyne. [12]
The Chichibabin reaction (pronounced ' (chē')-chē-bā-bēn) is a method for producing 2-aminopyridine derivatives by the reaction of pyridine with sodium amide.It was reported by Aleksei Chichibabin in 1914. [1]
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A metal acetylide is formed in situ when an alkyne is treated with a strong bases such as a hydroxide or an alkoxide: [3] HC≡CH + KOH ⇌ HC≡CK + H 2 O; RR'C=O + HC≡CK ⇌ RR'C(OK)C≡CH; The metal acetylide then reacts with an aldehyde or ketone to form a propargyl alcohol.
Once a terminal alkyne is achieved, the 3-aminopropylamine anion will attack and remove the terminal proton. However, the process stops there because the carbon-hydrogen bond electrons cannot form an additional pi-bond on top of the alkyne. [3] [1] Therefore, an acetylide anion is produced. A mild acid workup will quench the acetylide anion and ...
Thus, few drops of diamminesilver(I) hydroxide (Ag(NH 3) 2 OH) reacts with terminal alkynes signaled by formation of a white precipitate of the silver acetylide. This reactivity is the basis of alkyne coupling reactions, including the Cadiot–Chodkiewicz coupling, Glaser coupling, and the Eglinton coupling shown below: [18]
This can react with almost all alkenes and alkynes, including styrenes and alcohols. This is especially useful, as the unmodified Simmons-Smith is known to deprotonate alcohols. Unfortunately, as in Pathway B shown the intermediate can also react with the starting diazo compound, giving cis- or trans- 1,2-diphenylethene.
In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne (−C≡CH) is added to a carbonyl group (C=O) to form an α-alkynyl alcohol (R 2 C(−OH)−C≡C−R). [1] [2] When the acetylide is formed from acetylene (HC≡CH), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation.