Search

A novel catalytic route for the direct synthesis of bis-oxazolidino-nedienes from CO2 and propargylic amines is presented. An inexpensive copper catalyst promotes the Glaser coupling and a subsequent double cyclization step. The obtained diene derivatives undergo polymerization in the solid state, showcasing a rare example of spontaneous topochemical polymerization. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A highly selective palladium‐catalyzed carbonylation of 2‐alkynylanilines bearing an amide moiety to condensed six‐membered heterocyclic structures has been developed under mild conditions (room temperature and atmospheric pressure of CO). The carbonylative protocol is also compatible with CO surrogates, such as benzene‐1,3,5‐triyl triformate (TFBen) or the newly developed calix[6]arenes functionalized with six formate groups (CLX[6]CO), which are both capable to release CO in situ. A series of tricyclic fused heterocycles containing the important oxazino‐quinolinone scaffold have been selectively obtained (only the 6‐endo‐dig cyclization mode has been observed) in good to excellent yields (up to 99%). [ABSTRACT FROM AUTHOR]

Propargyl ureas can lead to a range of possible heterocyclic compounds, mainly depending on the employed catalyst. Silver salts are known to promote the N-5-exo-dig cyclization mode to imidazolidinone derivatives. Conversely, a versatile and stereoselective O-5-exo-dig cyclization of propargyl ureas to 2-aminooxazolines by Ag(I) catalysis is here disclosed. Good to excellent yields and complete stereoselectivity of the external double bond have been achieved under milder reaction conditions (50-60 °C). A one-pot protocol starting from the corresponding propargylic amines and isocyanates has been developed as well. N,N'-Dipropargyl ureas underwent a uncommon O-5-exo-dig/N-5-endo-dig double cyclization sequence. Finally, insights into the tautomeric equilibrium of 2-aminooxazoles and on their relative reactivity are provided. [ABSTRACT FROM AUTHOR]

Highly substituted 1H-isochromenes, isobenzofurans and pyranopyridines are prepared by allowing o-(1-alkynyl)arenecarboxaldehydes and ketones to react with I2, ICl, NIS, Br2, NBS, p-O2NC6H4SCl or PhSeBr and different alcohols or carbon-based nucleophiles at room temperature. Naphthyl ketones and iodides can be prepared by the reaction of 2-(1-alkynyl)arenecarboxaldehydes with I2 and simple olefins or alkynes.

The heterocyclic ring formation by means of PdI2-catalyzed oxidative cyclization-alkoxycarbonylation reactions to aliphatic acetylenic ketones is investigated. It is found that cyclopentenone, dihydropyridinone and tetrahydropyridinedione derivatives, formed when the reaction is carried out at higher temperature and for a long time, can also be selectively obtained through an acid treatment of tetrahydrofuran and oxazoline derivatives.

The synthesis of 4H- 3,1-benzoxazines, quinazolin-2-ones, and quinoline-4-ones is described by using a palladium-catalytic system. These nitrogen heterocycles are used as intermediaries for the further preparation of dyestuffs and of pharmaceutical products, as they exhibit a wide range of biological activity.

o-Biaryl carbaldeydes and ketones are obtained through the one-pot reaction of o-aryl iodides with o-bromobenzyl alcohols under the catalytic action of Pd and norbornene, in the presence of a base. The same reaction can also give dibenzopyrans by Pd and norbornene catalysis with a different termination, leading to C–O ring closure. In both cases the process first leads to a five-membered palladacycle, which controls C–C coupling, then to a seven-membered oxapalladacycle, which gives aldehydes and ketones or dibenzopyrans. [ABSTRACT FROM AUTHOR]

Ab initio calculations in the gas-phase indicate that the substitution of an ethylene with a propylene moiety in the polyether bridge of 1,3-di-iso-propoxycalix[4]arene-crowns-6 could result in an enhanced Cs+/K+ selectivity which is of particular interest in nuclear waste treatment. We therefore synthesised two novel calix[4]arene-crown-6 compounds ( and ) having a propylene moiety in their structure and for this named calix[4]arene-propylene-crown-6. The structures of compounds and were elucidated by NMR in solution and for also by X-ray diffraction studies in the solid state. Association constants (Ka) in CHCl3 of the two novel calix-crowns were measured and pointed out a plateau selectivity towards alkali metal ions which was not predicted by molecular modelling calculations. These results indicate the important role played by the solvent molecules and counter-anions in binding for this class of ionophores. [Copyright &y& Elsevier]

Selectively substituted biaryls containing a ketone unit are obtained under mild conditions in satisfactory yields by a simple reaction of ortho-substituted aryl iodides and ketones in the presence of palladium and norbornene as catalysts. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A highly selective palladium‐catalyzed carbonylation of 2‐alkynylanilines bearing an amide moiety to condensed six‐membered heterocyclic structures has been developed under mild conditions (room temperature and atmospheric pressure of CO). The carbonylative protocol is also compatible with CO surrogates, such as benzene‐1,3,5‐triyl triformate (TFBen) or the newly developed calix[6]arenes functionalized with six formate groups (CLX[6]CO), which are both capable to release CO in situ. A series of tricyclic fused heterocycles containing the important oxazino‐quinolinone scaffold have been selectively obtained (only the 6‐endo‐dig cyclization mode has been observed) in good to excellent yields (up to 99%). [ABSTRACT FROM AUTHOR]