Preparation of Some heterocyclic enones and ynones by isomerisation of the propargylic alcohols

Abstract

The propargylic alcohols were synthesised by treatment of aldehydes with substituted acetylenes. The conversion of propargylic alcohols to propynones and propenones takes place with pyridine hydrochloride in methanol at room temperature. In presence of pyridinium triflate and p-toluenesulfonate the propynone was the only product isolated in the isomerisation of alcohol. The silylated propenone undergoes with cyclopentadiene a Diels–Alder cycloaddition to give ketone whose skeleton is related to that of quinine.

One‐Pot Alkynylation of Azaaryl Aldehydes and Spontaneous Base‐Free Rearrangement into Enone Esters: an Autoinductive Mechanism

“…[40,41] Consequently, in our case, it is reasonable to envision two molecules of propargylic alcohols bearing a pyridine ring reacting with each other, one acting as the base to effect the isomerization, making the process autocatalytic. In contrast, Biellman et al reported that catalytic amounts of pyridine hydrochloride promoted isomerization of pyridine alkynol by ring activation at C-2 and C-4.…”

“…In contrast, Biellman et al reported that catalytic amounts of pyridine hydrochloride promoted isomerization of pyridine alkynol by ring activation at C-2 and C-4. [40,41] Consequently, in our case, it is reasonable to envision two molecules of propargylic alcohols bearing a pyridine ring reacting with each other, one acting as the base to effect the isomerization, making the process autocatalytic. To identify some of the intermediates of the reaction pathway, the following reaction aimed to trap the allenolate intermediate (Scheme 2): pyridine-2-carboxaldehyde was let to react with dimethylzinc and ethyl propiolate under standard conditions and analytical samples monitored the progress of the reaction.…”

Synthesis, characterization, and antioxidant activity of heterocyclic Schiff bases

“…The synthesis of aromatic compounds is of great importance due to the wide variety of uses. [1][2][3][4][5][6][7][8] The Schiff bases (SBs) have gained great interest owing to the wide range of their applications nowadays. The SBs, defined by an imine or azomethine (−CH = N−) group, are mostly synthesized by the condensation reaction of carbonyl compounds (aldehyde or ketone) with compounds consisting of amine moiety.…”