Some novel reactions of alkynes with cationoid electrophiles in nitroalkane solutions

Brønsted Acid‐Mediated Hydrative Arylation of Unactivated Alkynes

“…[16,17] Examples include the gold-and mercurycatalyzed addition of sulfoxideso rN-oxides to alkynes as well as iridium catalysis. [18,19] Herein we describe the synthesis of a-arylatedk etones by an atom-economical, Brønsted acid-catalyzed hydrative arylation of alkynes using sulfoxides.…”

Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones

“…Treatment of 5-hexynoic acid with trifluoroacetic anhydride followed by decomposition of the reaction mixture in methanol under reflux yielded 1,3-cyclohexandione in 25% yield. Later, Smit and coworkers reported the closely related acyclic reaction between alkynes and acyl cations leading to β-diketones in 25–76% yield [ 8 – 9 ]. Interestingly, only reactions run in mildly nucleophilic solvents, such as nitromethane, yielded products.…”

“…Building on the work of Tedder [ 7 ] and Smit [ 8 – 9 ] we have improved the alkynoic acid cyclization approach in a manner that allows ready access to 3-alkoxy-2-cyclohexenones in good yields. Further elaboration of this methodology is ongoing.…”

Acetyl Chloride

“…Under Friedel-Crafts conditions (AcCl/AlCl 3 , CCl 4 , 0-5 • C), acetylene undergoes acetylation to afford β-chlorovinyl methyl ketone in 62% yield 4 and under similar conditions (AcSbF 6 , MeNO 2 , −25 • C) 5-decyne undergoes acetylation to afford 6-acetyl-5-decanone in 73% yield. 65 Acetylation of Saturated Alkanes. Saturated alkanes, on treatment with a slight excess of AcCl/AlCl 3 at elevated temperature, undergo dehydrogenation (by hydride abstraction followed by deprotonation) to alkenes, which undergo acetylation to afford vinyl methyl ketones.…”