Iron(III)‐Catalyzed Hydration of Unactivated Internal Alkynes in Weak Acidic Medium, under Lewis Acid‐Assisted Brønsted Acid Catalysis

Abstract

Alkylarylalkynes are converted with full regioselectivity into the corresponding arylketones by formal hydration of the triple bond under weak acidic conditions, at times and temperatures (� 95°C) comparable to those used for terminal alkynes. The process catalyzed by Fe 2 (SO 4 ) 3 nH 2 O in glacial acetic acid exhibits good functional group compatibility, including that with bulky triple bond substituents, and can be extended to the one-pot transformation of aryltrimethylsilylacetylenes into acetyl derivatives via a desilylationhydration sequence. The overall reactivity pattern along with proton affinity data indicate that the triple bond is activated by proton transfer rather than by π-interaction with the metal ion. This mechanistic feature, at variance with that of noble metal catalysts, accounts for the total regioselectivity and the insensitivity to steric hindrance exhibited by the Fe 2 (SO 4 ) 3 nH 2 O/AcOH catalytic system.

Total Synthesis of Leptosperol B through Stereocontrolled Intramolecular 1,4-Addition to Construct the Octahydronaphthalene Framework

“…Condition with Hg­(OAc) 2 in AcOH unfortunately gave a complex mixture. However, replacement of Hg­(OAc) 2 with Fe 2 (SO 4 ) 3 n H 2 O in AcOH was effective to afford hydrated products 17 and 18 , but regrettably, regioselectivity proved to be opposite according to 1 H NMR analysis, indicating allylic hydration, not benzylic. This unsuccessful outcome prompted us to select substrate 14 without the unfavorable allylic position.…”

Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes

“…Catalytic hydration of alkynes has historically been facilitated by Hg­(II) and strong Brønsted acids . Alternative catalyst systems have been sought owing to the toxicity of Hg­(II), and some very efficient Au, Pt, Fe, and Co catalysts have emerged that require only mild Brønsted acid or acid-free conditions. − The stability and recyclability of 1-PdBF 4 makes it a potentially appealing catalyst for alkyne hydration. Indeed, 1 mol % 1-PdBF 4 catalyzes the hydration of phenylacetylene to acetophenone in 95% yield after 5 h at 60 °C using a 1/1 (v/v) mixture of MeOH and water as solvent (Table ).…”

A Bimetallic Porphyrin Metal Organic Framework as Multifunctional Catalysts for CO2 Cycloaddition and Alkyne Hydration

“…Acidity has been found to play an important role in alkyne hydration due to acids involve the enol and subsequent keto enol tautomerization by affecting the rate limiting protonation of the carbon-carbon triple bond. [54][55] The effect of common acids on the AH is analyzed using phenylacetylene as a model substrate to establish optimal condition (Table 1). With methanol as solvent only a small amount of acetophenone is synthesized after the addition of CH 3 COOH (Entry 7).…”