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Selective Phosphoranation of Unactivated Alkynes with Phosphonium Cation To Achieve Isoquinoline Synthesis

Hong Cui1, Jinku Bai1, Tianyu Ai1

  • 1Department of Chemistry, Capital Normal University, Beijing 100048, People's Republic of China.

Organic Letters
|May 7, 2021
PubMed

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Preparation of Alkynes: Alkylation Reaction02:27

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Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
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Introduction
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Electrophilic Addition to Alkynes: Halogenation

Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
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Direct alkylation of ammonia produces polyalkylated amines, along with a quaternary ammonium salt. To exclusively prepare primary amines, the azide synthesis method can be used.
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