Related Experiment Video
Updated: Jun 18, 2026
Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes
Published on: September 8, 2013
A hydrido-alkynyl-Prins cyclization using isopropanol as a hydride donor: discovery, scope and mechanistic study
Gollachinnamola Ramesh1, Surabhi Mishra1, Beeraiah Baire1
1Department of Chemistry, Indian Institute of Technology Madras, Chennai-600036, India. beeru@iitm.ac.in.
None:
The alkynyl-Prins cyclization is a very important strategy in organic synthesis for the construction of cyclic frameworks and natural products, via a vinyl carbocation intermediate under acid catalysis. Surprisingly, the alternate alkynyl-Prins cyclization (between an alkyne-tethered aldehyde/ketones and an external alcohol) has been less explored. Herein, we have designed and developed an unprecedented hydrido-alkynyl-Prins cyclization, which involves an alternate alkynyl-Prins cyclization, [1,5]-hydride migration, and SN2' nucleophilic substitution cascade. In this reaction, various alcohols, such as isopropanol, were employed as hydride donors. A broad scope has been observed for the alkyne-aldehydes and alcohols, for the construction of the corresponding chromenes, 1,2-dihydroquinolines, and phenanthrenes, by respectively employing oxygen, nitrogen and carbon tethered alkyne-carbaldehydes. Performing an experiment with a deuterated sec-alcohol and isolating the corresponding di-deuterated ether and ketone supported the proposed mechanism involving a [1,5]-hydride migration. When the reaction was performed in the presence of H218O, the enhanced yield of the ketone (58% from 13%) and the presence of 18O in it (HRMS-analysis) clearly suggested the formation of the ketone, possibly via the competitive trapping of the vinyl carbocation by water.
More Related Videos
07:30A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones
Published on: January 21, 2020
10:12Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols
Published on: April 4, 2014
Related Concept Videos
02:47Alkynes 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.
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
02:41Formation of Halohydrin from Alkenes
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
02:34Preparation of Alkynes: Dehydrohalogenation
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.