Related Experiment Video
Updated: Oct 17, 2025
09:58
Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
11.4K
Borylative Cyclization of 1,6-Allenynes Driven by BCl3
Chun-Hua Yang1, Xiangkun Sun1, Congcong Niu1
1Henan Key Laboratory of New Optoelectronic Functional Materials, College of Chemistry and Chemical Engineering, Anyang Normal University, 436 Xian'ge Road, Anyang 455000, People's Republic of China.
Organic Letters
|October 6, 2021
Summary
A novel metal-free cyclization reaction using boron trichloride (BCl3) efficiently creates pyrrolidines and dihydroazepines. This method offers a versatile route to complex organic molecules with quaternary carbon centers.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Catalysis
Background:
- Intramolecular borylative cyclization is a key transformation in organic synthesis.
- Developing metal-free catalytic systems remains a significant challenge.
- 1,6-Allenynes are versatile precursors for constructing cyclic compounds.
Purpose of the Study:
- To develop a novel metal-free intramolecular borylative cyclization of 1,6-allenynes.
- To explore the utility of boron trichloride (BCl3) as a catalyst for this transformation.
- To investigate the synthesis of pyrrolidine and 3,5-dihydroazepine derivatives.
Main Methods:
- The study employed a metal-free intramolecular borylative cyclization reaction.
- Boron trichloride (BCl3) was used as the driving force for the cyclization.
- The reaction conditions were optimized to control the formation of different cyclic products based on substrate substituents.
Main Results:
- A general and practical method for the synthesis of pyrrolidines and 3,5-dihydroazepines was established.
- The reaction successfully constructed pyrrolidines containing all-carbon quaternary centers.
- Substituent-controlled synthesis yielded either pyrrolidines or 3,5-dihydroazepine derivatives, with phenyl groups favoring the latter.
Conclusions:
- The developed metal-free borylative cyclization offers an efficient route to valuable heterocyclic compounds.
- The reaction's selectivity can be tuned by altering the substituents on the allene moiety.
- This methodology provides a practical strategy for accessing complex organic structures.
Related Concept Videos
02:46Halogenation of Alkenes
16.8K
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
16.8K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
19.2K
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
19.2K
01:27Radical Substitution: Allylic Bromination
5.7K
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
5.7K
02:38Electrophilic Addition to Alkynes: Halogenation
8.9K
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.
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.
8.9K
01:14Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
2.9K
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
2.9K
02:27Preparation of Alkynes: Alkylation Reaction
10.9K
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.
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.
10.9K