Synthesis and spectroscopic and structural studies of cross-conjugated dienones derived from cyclic ketones and aromatic aldehydes

Abstract

Cross conjugated dienones were synthesized by the reactions of cyclic ketones with two equivalents of aromatic aldehydes under basic conditions. An NMR spectroscopic study and X ray diffraction analysis demonstrated that all reaction products are formed as E,E isomers. Spontaneous photochemical trans-cis isomerization of cross conjugated dienones under the scattered light in solution was observed for the first time. The degree of isomerization depends mainly on the nature of the central fragment of the dienone molecule. The previously unknown product of photochemical [2+2] cycloaddition of 2,5 bis[(E) (3 pyridyl)methylidene]cyclo pentanone was synthesized and characterized by spectroscopic methods and X ray diffraction. Under the conditions used, only one isomer of the cyclobutane adduct was obtained.

Lewis Acids as Mild and Effective Catalysts for the Synthesis of 3,5‐Bis[(hetero)arylidene]piperidin‐4‐ones

“…The structures of the known 3,5-bis[(hetero)arylidene]piperidin-4-ones 2a [18], 2c [19], 2e [20], 2f [21], and 3a [22] obtained via Methods A and B as free bases were confirmed by the multinuclear NMR spectra. Their physicochemical constants fit well the available literature data.…”

Novel Linear Bis-Crown Receptors with Cross-Conjugated and Conjugated Central Cores

“…In the paper, cyclopentanone is selected as the central moiety, since it is known that its dienone derivatives are characterized by a high degree of conjugation of all multiple bonds, due to an almost perfectly flat conformation of molecules. [29] The registered electron absorption and fluorescence spectra of the dienones 1a-g show the following features (Table 1, Figure 2). All dienones have an intense longwave absorption band (LWAB) with λ max of 345 nm (for 1a)…”

“…[26] Double bonds of dienones allow for trans-cis-photoisomerization and [2+2]-photocycloaddition reactions. [29] PCA itself and its stereoselectivity can be controlled by supramolecular preorganization of double bonds, to create the most suitable geometry of the starting dimer. [30][31][32][33][34] We have previously shown that bis-crown stilbenes can form unusual bi-and exotic trimolecular complexes in the reaction with diammonioalkyl derivatives of viologen or cyanine dyes, [35][36] due to the formation of a system of hydrogen bonds.…”

Synthesis of Biologically Active Chalcon Analogues via Claisen-Schmidt Condensation in Solvent-Free Conditions: Supported Mixed Addenda Heteropoly Acid as a Heterogeneous Catalyst

“…In the spectra of compounds, the signals for the protons of the CH= group appear at δ 7.41-7.81. It is known [26][27][28] that the Z isomers are characterized by the chemical shifts at δ ~6.8, whereas the signals for the E isomers should appear at higher field than 7.2 ppm.…”