(4Z,6Z)-4,6-Bis(4-meth­oxy­benzyl­idene)-2,2-dimethyl-1,3-dioxan-5-one

The title compound, C22H22O5, crystallizes with two independent mol­ecules in the asymmetric unit, both of which possess pseudo-C s symmetry. The central 1,3-dioxanone rings have envelope conformations, with the C atom bearing the two methyl groups at the flap. The benzene rings of the meth­oxy­benzyl­idene units, attached in the 4- and 6-positions on the central 1,3-dioxanone rings, are tilted in the same direction with dihedral angles varying between 8.2 (1) and 18.1 (1)°. The crystal packing is influenced by π-stacking inter­actions of the parallel displaced type [centroid–centroid distance of 3.723 (1) Å for mol­ecule 1 and 3.884 (1) Å for mol­ecule 2, with ring slippages of 1.432 and 1.613 Å, respectively] and the T-shaped type, with the long mol­ecular axes all aligned along [010]

rac-3-[(3-Chloro­anilino)(4-chloro­phenyl)meth­yl]thian-4-one

In the title compound, C18H17Cl2NOS, the thio­pyran­one ring adopts a chair conformation, with the substituent in the axial position. The dihedral angle between the two benzene rings is 89.43 (1)°. In the crystal, mol­ecules form inversion dimers through inter­molecular N—H⋯O hydrogen bonds [graph set R 2 2(8)]

(2E,6E)-2,6-Bis(4-methyl­benzyl­idene)cyclo­hex-3-en-1-one

The title compound, C22H20O, shows an approximately planar cyclo­hexenone ring [maximum deviation = 0.069 (4) Å], with a disordered position of the C=C bond [ratio = 0.71 (2)/0.29 (2)]. The benzene rings of the 4-methyl­benzyl­idene units, attached in the 2- and 6-positions to the cyclo­hexenone ring, are rotated in the same direction by 28.6 (4) and 22.4 (4)°, with respect to the mean plane of the cyclo­hexenone ring [fraction 0.71 (2); maximum deviation = 0.06 (3) Å]. In the crystal, mol­ecules are packed in the manner of a distorted hexa­gonal rod packing with their long axes all aligned along [201]. A number of C—H⋯π inter­actions stablize the crystal structure

rac-3-[(Anilino)(naphthalen-2-yl)­methyl]thian-4-one

In the title compound, C22H21NOS, the thio­pyran­one ring adopts a chair-like conformation with the substituent in the axial position. The relative configuration of the racemic compound is 3R,7S according to the numbering scheme used in this publication. In the crystal packing, centrosymmetric dimers are built up via N—H⋯O hydrogen bonds, with graph set R 2 2(8)

A green, inexpensive and efficient organocatalyzed procedure for aqueous aldol condensations

A facile and general procedure is presented for diethylamine-catalyzed double crossed aldol condensation of cyclic ketones with various aromatic aldehydes under aqueous conditions. Excellent yields of 3,5-bisarylmethylidenes of homocyclic and heterocyclic ketones are achieved in a one-pot procedure. Furthermore, the methodology is efficiently applied to the synthesis of chalcones from their corresponding methyl ketones. In the majority of the cases studied, products precipitate from the reaction mixtures and the medium is recycled in subsequent several reactions without significant loss of activity

Lewis acid catalyzed and self-assembled diels-alder reactions (LACASA-DA) : a new strategy to control diels-alder reaction

The first comprehensive account of Diels-Alder reactions occurring by a simultaneous self-assembly of the components and catalysis of the reaction via a Lewis Acid (LA) is presented in this study. The synthetic usefulness of the intramolecularity achieved by temporary connection of DA reaction components has been combined with the benefits of LA catalysis to overcome the regio- and stereochemical diversities associated with DA reactions of unsymmetrically substituted dienes and dienophiles. LA's employed in this study act both as temporary connectors (by binding to LB sites of the diene and dienophile) and as catalysts (by complexation to oxygen of carbonyl moieties of the dienophiles). Formation of the tether, cycloaddition; and removal of the transient linker all occurs in a single operation.* To illustrate the high selectivity accomplished in this approach, an experimental model system consisting of unsymmetrically substituted dienol 6 and methoxy diene 397 and an unsymmetrically substituted dienophile (methyl acrylate, MAC) was designed. Thermal combination of either of these two dienes with MAC produces nearly equimolar mixtures of all four possible adducts illustrating the unselective nature of the reactions. Use of LA's to mediate the reaction between dienol 6 and MAC results in exclusive regio- and stereoselective formation of a single adduct. In contrast, application of the same LA's for the reaction between the methoxy diene and MAC either results in the formation of two 'endo' regioisomers in low yield or no reaction at all.* Exclusive formation of a single adduct for the reactions of 6 is attributed to a process in which the LA both pre-organizes the reactants and catalyzes the cycloaddition. This phenomenon is not expected to be observed in the reactions of the methoxy diene. The difference in the behavior of the two dienes is ascribed to the difference in their interactions with the LA's. Dienol 6 is able to bind covalently and irreversibly to the LA's while methoxy diene 397 is only able to co-ordinate to the LA's in a reversible manner. Mechanistic studies strongly support the self-assembled pathway and exclude other potential routes. Reactions of dienol 6 with other structurally suitable dienophiles under similar LA mediated conditions exhibit higher selectivities and reactivities in comparison with their uncatalyzed counterparts. Use of a structurally similar chiral dienol induces a highly diastereoselective cycloadditions with different dienophiles, whereas the thermal versions of the reactions again produce all possible adducts. The strategy has also been used for DA reactions of ' 2H'-thiopyran dienols with dienophiles 'N'-acroyl-2-oxazolidinone (NAO), ('E')-3-[3-(methoxycarbonyl)propenoyl]-1,3-oxazolidin-2 -one (MCPO), and 'N'-phenylmaleimide (NPM). Use of MgII is demonstrated to be effective to stereoselectively catalyze reactions which are unselective thermally or do not proceed at all. *Please refer to dissertation for diagrams

Synthesis and fluorescence studies of novel bisarylmethylidene derivatives of 2-methoxy-2-methyl-1,3-dioxan-5-one

The first general procedure is described for the synthesis of novel bisarylmethylidenes of 2-methoxy-2-methyl-1,3-dioxan-5-one 1. Thus, several derivatives of 3 are obtained rapidly in high yields by reacting 1 with different aldehydes in the presence of catalytic quantities of pyrrolidine in EtOH at rt. Upon completion of the reactions, products are obtained directly by spontaneous precipitation avoiding time consuming and expensive chromatographic separations. All products were characterized by proton and carbon NMR spectroscopy methods, and in one case, the proposed structure was elucidated by X-ray crystallography, confirming the Z stereochemistry for the olefinic C=C bonds. Due to showing different colors in solid and solution states, products were studied for their photophysical properties as well.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Tandem aldol condensation-Diels–Alder-aromatization sequence of reactions: a new pathway for the synthesis of 2-tetralone derivatives

A series of new polysubstituted derivatives of 2-tetralones possessing two ester groups were synthesized via a tandem aldol condensation-Dielsâ Alder-aromatization sequence of reactions. All the three steps took place in one pot and in the presence of aminofunctionalized silica coated Fe3O4 nanoparticles as the catalyst. In situ formed dienes reacted with diethyl acetylenedicarboxylate at room temperature and the process was followed by spontaneous aromatization of the cycloadducts to produce high yields of the final tetralone products. Further studies suggest that the process goes through an initial aldol condensation-cycloaddition sequence followed by oxidation and rearrangement steps. After completion of the reactions, the catalyst could be recycled and reused efficiently in next reactions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author