Convenient Synthesis of (E)‐5‐Aryl(halo)methylenebicyclo‐ [2.2.2]oct‐2‐enes and ‐[2.2.1]hept‐2‐enes via Lewis Acid‐ Promoted Carbohalogenation of Cyclic 2,6‐Enynols

Abstract

An efficient synthesis of (E)-5-aryl(halo)methylenebicyclo[2.2.2]oct-2-enes is reported. Lewis acid-promoted carbohalogenation of 4-(3-arylprop-2-ynyl)-cyclohex-2-enols in dichloromethane proceeds rapidly to afford the exo-methylenebridged bicycles in good yields. This method also provides an easy access to (E)-5-aryl(halo)methyl-A C H T U N G T R E N N U N G enebicyclo[2.2.1]hept-2-enes from the five-membered ring 2,6-enynols. The reactions are procedurally simple and high yielding, producing the aryl(halo)methylene-bridged bicycles in minutes under air and mild conditions.

Fe‐Catalysed Coupling Reactions Between Alkynes and Alcohols

“…). [20] In 2015, Jana et al, introduced an effective method for the synthesis of 9,10-substituted phenanthrenes 54 from 2alkynyl-biphenyl-2-carbinols 55 using Fe(OTf) 3 as a catalyst, through an intramolecular isomerizative coupling of alcohols and alkynes (Scheme 18). [21] The dihydrophenanthrene 56 was found to be the first product to form.…”

Visible-Light-Initiated Na2-Eosin Y Catalyzed Highly Regio- and Stereoselective Difunctionalization of Alkynes with Alkyl Bromides

“…Among these transformations, simultaneous addition of a C­(sp 3 )–X (X = halogens) bond to alkynes has been proven to be an effective protocol for the synthesis of alkenyl halides, which are valuable intermediates in diverse of transition-metal-catalyzed cross-coupling reactions. In the reported works, various additions of C–X to alkynes for the preparation of vinyl halides were usually conducted in the presence of transition-metal salts, such as Pd, Fe, Cu, Zn, etc. as catalysts .…”

Highly Stereoselective Intramolecular Carbofluorination of Internal α,β-Ynones Promoted by Selectfluor

“…In 2016, Zhang and co-workers reported the Ag-catalyzed radical ring expansion/fluorination of ethynyl cyclobutanols with Selectfluor . In addition, BF 3 ·Et 2 O and Ph 3 CBF 4 could be used as Lewis acids and fluoride sources to react with enynols to afford tetrasubstituted monofluoroalkenes via formation of allylic carbocation intermediates. Recently, Tobisu and co-workers reported the organophosphine-catalyzed intermolecular carbofluorination of alkynes to produce tetrasubstituted monofluoroalkene derivatives with a low E/Z ratio (Scheme b) .…”