Metal-Free, Site-Selective Addition to Ynones: An Approach to Synthesize Substituted Quinoline Derivatives

Abstract

An efficient two component cycloaddition reaction to synthesize various substituted quinoline derivatives was developed. Ynone 1 was functionalizated by N-oxide attacking the C3-oxetium site and C3-site regioselectively to give 3 and 4. Analogues 3k and 4v have a high binding constant with Hg in CHCN.

Heteroarene N‐Oxides as Oxygen Source in Organic Reactions

“…The majority of catalytic alkyne oxidation reactions by heteroarene N ‐oxides proceed through Lewis‐acid activation of the alkynes and subsequent nucleophilic attack by the nucleophilic oxygen of the N ‐oxide. Gold(I) complexes are prevalent in this context, but rhodium, copper, zinc, and non‐metal‐catalyzed examples have also been reported.…”

“…Other examples comprise cycloaddition reactions of ynones, diynes and enynones with quinoline and isoquinoline N ‐oxides, and meta ‐selective alkyne oxyarylation with pyridine N ‐oxides …”

Tandem Reactions of Ynones: via Conjugate Addition of Nitrogen‐, Carbon‐, Oxygen‐, Boron‐, Silicon‐, Phosphorus‐, and Sulfur‐Containing Nucleophiles

“…N ‐Oxides, including quinoline N ‐oxides or isoquinoline N ‐oxides, N ‐methylnitrones and in situ generated N ‐oxides, could be incorporated in the final products. Usually, no metal catalyst was required (Scheme ).…”

“…The Ji group has described two cycloaddition reactions to yield substituted phenanthrenes 102.4 [Eq. (102‐1)] and 1,3‐diketones 102.5 [Eq.…”

Synthesis of ynones at room temperature catalyzed by copper chloride cryptand complex under solvent free conditions

“…Ynones are the constructive building blocks in organic chemistry that are used as synthetic intermediates for the preparation of many biologically-active compounds, heterocyclic derivatives [1] etc. Ynones are also precursors for the synthesis of various valuable organic functional groups like isoxazoles [2a], pyrimidines [2b], quinolones [3], furans [4], pyrazoles [5], flavones [6], oximes [7], polyfunctionalized pyrroles [8], chiral propargylic alcohols [9] and many more. There are various reaction protocols that have been reported for the synthesis of ynones which include oxidation of propargylic alcohols [10], coupling reactions of terminal alkynes with organic halides in the presence of carbon-monoxide gas [11], oxidation of alkynes [12], reaction of terminal alkynes with nitriles [13], and the most important method is the reaction between terminal alkynes and carboxylic acid derivatives in the presence of various strong bases [14] and elements such as silver [15], zinc [16], tin [17], silicon [18], lithium [19], copper [20], magnesium [21], cadmium [22], aluminum [23], thallium [24], gallium [25], stibium [26], indium [27], etc.…”