Dehydration-hydration of α-alkynols over zeolite catalyst. Selective synthesis of conjugated enynes and α,β-unsaturated ketones

Photo‐Cross‐Coupling Reaction of Electron‐Rich Aryl Chlorides and Aryl Esters with Alkynes: A Metal‐Free Alkynylation

“…Precedents for the migration of a methyl (or a methylene) group adjacent to a vinyl cation have been reported,34 but examples that lead to an α‐hydroxy cation are rare 35. Moreover, formation of the enone 19 as the Z isomer demonstrates a new route to the synthesis of related compounds which are currently accessible by the Rupe or Meyer–Schuster rearrangement 36…”

Selective synthesis of conjugated enynes from α-arylalkynols using LiCl-Acidic Al2O3 under solvent-free conditions

“…80, 27.21, 87.85, 94.60, 123.82, 126.92, 128.68, 128.70, 132.35, 136.30, 197.71 250,248,226,224,210,208,184,182,156,154,139,128,114,113,75 1',]benzene (8B): Yield 80%, pale yellow solid; m.p. 97.5-98.5°C; IR(KBr, cm -1 ), 3060, 2938, 2200, 1608, 1500, 1315, 908, 846; 1 10,82.25,92.20,122.34,122.60,126.76,131.40;MS m/e 206,191,189,176,165,141;Anal. calcd for C 16 H 14 : C,93.20;H,6.80,found: C,93.05;H,6.87.…”

“…2 1,3-Enynes are conjugated systems that can be specially used in the synthesis of natural products, 3 polymers 4 and in the selective construction of aromatic frameworks. 5 There are many synthetic approaches to these compounds, most of which include coupling of terminal alkynes with vinyl halides or triflates and vinyl organometallic compounds, 6 homocoupling or cross-coupling of acetylenes using metal catalysts such as Pd 7 and Ru complexes, 8 or dehydration of α-alkynols using reagents such as dicobalthexacarbonyl complexes, 9 acidic zeolites, 10 and polyphosphoric acid trimethylsilyl ester. 11 Although all these methods have their own advantages, the scope of many of these reactions has been limited by the nature of the reactants or the procedure employed.…”

Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

“…One of the most used synthetic methods is palladium-catalyzed cross-coupling reactions, e.g., Sonogashira reactions ( Adamson et al, 2019 ) or Heck-type reactions ( Wen et al, 2011 ) which are generally performed in excellent yields and good regio- and defined stereoselectivities ( García-Garrido, 2014 ). Besides, the Wittig olefination ( Karatholuvhu and Fuchs, 2004 ) of propargylic aldehydes/ketones, elimination reactions starting from propargylic alcohols ( Sartori et al, 1996 ; Ye et al, 2018 ) for the construction of the carbon-carbon double bond, or rearrangement reactions in Corey-Fuchs-type reactions ( Shi Shun and Tykwinski, 2003 ) of vinyl ketones have been described. One big drawback of all mentioned synthetic methods is the rather low atom economy for olefination or rearrangement reactions and the synthesis of the used starting materials, e.g., alkynyl-bromides or iodides (light-sensitive materials) or vinyl-halides.…”