Michael Addition of 3-Oxo-3-phenylpropanenitrile to Linear Conjugated Enynones: Approach to Polyfunctional δ-Diketones as Precursors for Heterocycle Synthesis.

Reaction of linear conjugated enynones, 1,5-diarylpent-2-en-4-yn-1-ones [ArC≡CCH=CHC(=O)Ar], with 3-oxo-3-phenylpropanenitrile (NCCHCOPh) in the presence of sodium methoxide MeONa as a base in MeOH at room temperature for 4-26 h affords polyfunctional δ-diketones as a product of regioselective Michael addition to the double carbon-carbon bond of starting enynones. The δ-diketones have been formed as mixtures of two diastereomers in a ratio of 2.5:1 in good general yields of 53-98%.

Stereoselective Synthesis of Multisubstituted Cyclohexanes by Reaction of Conjugated Enynones with Malononitrile in the Presence of LDA.

Reaction of linear conjugated enynones, 1,5-diarylpent-2-en-4-yn-1-ones, with malononitrile in the presence of lithium diisopropylamide LDA, as a base, in THF at room temperature for 3-7 h resulted in the formation of the product of dimerization, multisubstituted polyfunctional cyclohexanes, 4-aryl-2,6-bis(arylethynyl)-3-(aryloxomethyl)-4-hydroxycyclohexane-1,1-dicarbonitriles, in yields up to 60%. Varying the reaction conditions by decreasing time and temperature and changing the ratio of starting compounds (enynone and malononitrile) allowed isolating some intermediate compounds, which confirmed a plausible reaction mechanism. The relative stability of possible stereoisomers of such cyclohexanes was estimated by quantum chemical calculations (DFT method).