Ag(I)‐Catalyzed Cyclizative Hydration of Alkynes and Propargylic Alcohols. A Mild Approach to 2‐Acylfuran Derivatives

Abstract

We developed a mild strategy for the synthesis of 2‐acylfuran derivatives via cyclizative hydration of propargylic alcohols and alkynes, under Ag(I) catalysis. This is the first report employing the propargylic alcohols and their derivatives as alkyne partners in the cyclizative hydration process. This process found very broad scope for propargylic alcohols, alkynes and tethers. The highly chemo‐selective cyclizative hydration of 6‐acetoxy‐hex‐2‐en‐4‐ynal substrates suggests that, the acetoxy directed hydration of alkyne is not operable under Ag‐catalysis conditions and hence propargylic acetates can also be conveniently employed for the synthesis of 2‐(acetoxyacyl)furans.

Activation of o-Propargyl Alcohol Benzaldehydes under Acetalization Conditions for Intramolecular Electrophile Intercepted Meyer–Schuster Rearrangement

“…Nucleophilic participation of the carbonyl function in similar substrates having two alkyl groups on the carbinol carbon in the presence of stoichiometric MsOH to form allenyl ethers has been proposed by Beeraiah and co-workers (Scheme b). In this case, thus formed allenyl ether subsequently transformed into 2-acylfurans via an intermolecular attack of water . Therefore, the nucleophilic participation of acetal formed under the reaction conditions offers a unique advantage to intercepted Meyer–Schuster rearrangement.…”

Ag(I) Catalyzed Cascade Approach to 2‐(α‐Hydroxyacyl)pyrroles

“…Only in case of m ‐methoxycarbonyl benzyl amine, the expected pyrrole 32 (45 %) was associated with 15 % of 2‐acylfuran 33 . Aniline and cyclopentyl amine were also underwent smooth reaction to give the pyrroles 34 (40 %) and 35 (35 %) respectively along with 10 % and 20 % of 33 .…”

Ag(I)-Catalyzed Tandem Reaction of Conjugated Ene-yne-ketones in the Presence of PhI(OAc)2 and Triethylamine: Synthesis of 2-Alkenylfurans

“…On the basis of these investigations and reports in the literature, − a plausible mechanism to rationalize this cyclization–olefination (Scheme ) is depicted in Scheme . First, the acetylenic carbon–carbon triple bond is activated by the coordination of enynone 1 with the Ag­(I) ion .…”

“…For this goal, some screening to expand to other metal species may prove necessary to find new systems. Among optional metals, the use of silver species has less been exploited . For example, Pattenden et al reported that AgNO 3 -assisted cyclization of enynone precursors provide 2-alkenylfuran .…”