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An unexpected FeCl3-promoted reaction of cyclic imine dibenzo[b,f][1,4]oxazepines with alkynes was studied, leading to a series of 4-substituted 3-(2-hydroxyphenyl)-quinolines. A variety of substituted cyclic imines and terminal alkynes (arylacetylenes, conjugated enynes, and 1,3-diynes) were used for this reaction type resulting in the formation of the corresponding products in yields ranging from 34 to 88%. A reasonable reaction mechanism involving a tandem reaction procedure was proposed on the basis of control experiments. The reaction sequence demonstrated herein represents an efficient, yet practical method for the synthesis of novel 4-substituted 3-(2-hydroxyphenyl)-quinoline derivatives.

Dibenzo[bc,fg][1,4]dithiapentalene (1) has previously been prepared by an intramolecular nucleophilic aromatic substitution (SNAr) reaction of 9-fluorodibenzo[b,d]thiophen-1-thiol (X, Y ˭ S). Instead, subjecting 9-fluorodibenzo[b,d]benzofuran-1-ol (X, Y ˭ O) to similar reaction conditions provided a macrocycle (5), as a result of an intermolecular SNAr cyclization, rather than dibenzo[bc,fg][1,4]dioxapentalene (3). To shed further light on this reaction type, we here present an attempt to prepare the mixed (O,S) compound dibenzo[bc,fg][1,4]xathiapentalene (7) from 9-fluorodibenzo[b,d]thiophen-1-ol (11, X ˭ S, Y ˭ O). However, like a previous strategy to make this molecule, the attempt failed. We rationalize the results by a computational study of the reaction energetics and profiles of the SNAr reactions.

Here we outline and discuss the state-of-the-art in organocatalytic dienamine activation of enals, classifying examples according to different reactive activation pathways., Chiral secondary amines are some of the most commonly used kinds of catalysts. They have become a reliable tool for the α- and β-activation of carbonyl compounds, via HOMO, SOMO or LUMO activation pathways. Recently, chemists have turned their attention to the development of novel organocatalytic strategies for remote functionalisation, targeting stereocentres even more distant from the catalyst-activation site, through dienamine, trienamine, and vinylogous iminium ion pathways (γ-, ε- and δ-positions, respectively). Here we outline and discuss the state-of-the-art in dienamine activation, classifying examples according to the different reactive activation pathways followed by the formed dienamine intermediate (1,3-, 1,5-, 2,5- and 4,5-functionalisation) and the reaction type developed, as determined by the structure and the nature of electrophiles and nucleophiles.

A general and controlled bidirectional growth strategy enable a very rapid and efficient construction of oligo(phenyleneethynylene)s possessing functional groups such as methylthio and thioacetate groups at both ends. The strategy employs only one reaction type with good to moderate yields to grow the conjugated chains. The synthesis is efficient and can give 23 benzene rings and 22 carbon–carbon triple bonds in the conjugated chains. The compounds are fully characterized by 1H and 13C NMR and UV/vis and fluorescence spectroscopy.

Highly stereoselective N -acyliminium ion coupling reactions of β-ketoester derived silyl enol ethers with enantiopure lactams derived from ( S )-malic acid are reported. This reaction type is applied in the synthesis of the enantiopure C-2 substituted lactam 27 , a plausible intermediate in a projected synthesis of ptilomycalin A.

This chapter covers the diverse range of heterocycles that have two six-membered rings with five or more heteroatoms at positions other than the ring junctions. The 7-azapteridine nucleus (the pyrimido[5,4-e]-1,2,4-triazines) that is present in natural products such as toxoflavin, fervenulin, and reumycin dominates the chapter, although there are significant contributions from the 6-azapteridines (the pyrimido[4,5-e]-triazines), the pyrazinothiadiazines, the pyrimidothiadiazines, and the recently discovered pyridotetrazines. The organization of the chapter follows reaction type and synthesis type and is not arranged according to ring system. Most of the syntheses covered start with one preexisting heterocycle (commonly a triazine) and are categorized according to the way that the remaining heteroatoms are disposed to the ring junction. Spectroscopic, thermodynamic, and theoretical aspects are dealt with, but concentrate necessarily on the more common heterocycles within this category, or upon interesting or unusual results.

The heteropolyanions of W, Mo, and V, which have found numerous applications, are formed simply by acidification of solutions of their oxoanions. Under similar conditions, these oxoanion precursors are not available for Nb, and Nb-oxo chemistry is dominated by formation of the Lindquist ion [Nb 6 O 19 ] 8– only. However, heteropolyniobate formation is favored in hydrothermal reactions of aqueous, alkaline precursor mixtures. Here we give two examples of heteropolyniobates formed by this general reaction type: K 12 [Ti 2 O 2 ][SiNb 12 O 40 ]·16H 2 O [1], which contains chains of silicododecaniobate Keggin ions, and Na 14 [H 2 Si 4 Nb 16 O 56 ]·45.5H 2 O [ 2 ], a new heteropolyanion structure type.