Quantum‐Chemical Modeling of One‐Pot Assembly of 1‐Formyl‐2‐Pyrazolines from Alkylaryl Ketones, Arylacetylenes, Hydrazine, and Formic Acid
Year: 2025
Type: article
Abstract: The assembly mechanism of 1‐formyl‐2‐pyrazoline from alkylaryl ketones, arylacetylenes, hydrazine and formic acid has been investigated in some detail using the B2PLYP‐D2/6‐311+G**//B3LYP/6‐31+G* quantum‐chemical approach. We ascertained that the first stage of the assembly involves the C ‐vinylation reaction of acetophenone with phenylacetylene catalyzed by the KOBu t /DMSO superbase, followed by the Z ‐ E isomerization of the dienolate ion. Neutralization of the latter leads to a mixture of α , β ‐ and β , γ ‐unsaturated ketones. The kinetically most favorable route for the subsequent assembly of 1‐formyl‐2‐pyrazoline is found to involve (i) addition of hydrazine to the C═C bond of the α , β ‐unsaturated ketone, (ii) cyclization of the β ‐hydrazinyl ketone, and (iii) formylation of 2‐pyrazoline. The β , γ ‐unsaturated ketone is found to convert into the β , γ ‐unsaturated formylhydrazone, which is consistent with experiment. The transformation of β , γ ‐unsaturated formylhydrazone to 1‐formyl‐2‐pyrazoline proceeds through the hydration of formylhydrazone, resulting in the formation of β , γ ‐unsaturated ketone, which subsequently isomerizes into the α , β ‐unsaturated ketone. The high barrier of the isomerization accounts for the long duration of the corresponding stage of the synthesis (1 h, 100 °C).
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
Award: G2345328270
OpenAlex ID: W4411449957