Fluoroform-Derived CuCF3 for Trifluoromethylation of Terminal and TMS-Protected Alkynes
1Department of Chemistry, The Chinese University of Hong Kong , Shatin, New Territories, Hong Kong, China.
Abstract:
An efficient trifluoromethylation reaction of alkynes using a fluoroform-derived CuCF3 reagent is described. The CF3 source is the inexpensive industrial waste fluoroform (CF3H). The air-stable CuCF3 reagent can be prepared in large quantities and is convenient to use. Synthetically useful trifluoromethylated alkynes containing a wide range of functional groups were successfully synthesized under mild conditions. Both terminal and TMS-protected alkynes gave the products in one step. The beneficial effect of a diamine ligand tetramethylethylenediamine (TMEDA) with the fluoroform-derived CuCF3 reagent was also demonstrated.
Related Concept Videos
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Preparation of Alkynes: Alkylation Reaction
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.
Electrophilic Addition to Alkynes: Halogenation
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.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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.
Halogenation of Alkenes
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.
Preparation and Reactions of Sulfides


