Intramolecular acylation of 3-oxo-2-piperidine-propionic acid derivatives. Synthesis of hexahydro-2-oxopyrano[3,2-b]pyridines

The intramolecular acylation of some δ-keto acids derived from 3-oxo-2-piperidinepropionic acid are described. Bicyclic enol lactones coming from an O-acylation reaction are obtained in all cases. The regioselec-tivity of these processes is discussed in terms of the acylating agent and the δ-keto acid structure. The procedure establishes a convenient synthesis of hexahydro-2-oxopyrano[3,2-b)pyridines.     

Self-assembly and magnetic properties of a double-propeller octanuclear copper(II) complex with a meso-helicate-type metallacryptand core

An octanuclear copper(II) complex possessing a dimer-of-tetramers structure self-assembles from a binuclear oxamatocopper(II) metallacryptand of the meso-helicate type; its magnetic behaviour is consistent with its unique double-propeller molecular topology.     

Density functional calculations of a tetradecametallic iron(III) cluster with a very large spin ground state

Density functional theory (DFT) calculations and Monte Carlo (MC) simulations are used to calculate the exchange interactions in the Fe(III) cluster [Fe14(bta)6O6(OMe)18Cl6], impossible to determine by conventional methods--the results support a huge ground state spin arising from competing antiferromagnetic interactions.     

A centred, elongated "ferric tetrahedron" with an S= 15/2 spin ground state

The reaction of anhydrous FeCl(3) with 1H-benzotriazole-1-methanol (Bta-CH(2)OH) in MeOH produces the pentanuclear complex [Fe(5)O(2)(OMe)(2)(Bta)(4)(BtaH)(MeOH)(5)Cl(5)], containing a distorted tetrahedron of four Fe ions centred on a fifth. The central Fe is antiferromagnetically coupled to the peripheral Fe ions resulting in an S= 15/2 spin ground state.     

Different supramolecular hydrogen bond structures and significant changes in magnetic properties in dinuclear mu 2-1,1-N3 copper(II) complexes with very similar tridentate Schiff base blocking ligands

Three new basal-apical, mu(2)-1,1-azide bridged complexes, [CuL(1)(N(3))](2) (1), [CuL(2)(N(3))](2) (2) and [CuL(3)(N(3))](2) (3) with very similar tridentate Schiff base blocking ligands [L(1) = N-(3-aminopropyl)salicylaldimine, L(2) = 7-amino-4-methyl-5-azahept-3-en-2-one and L(3) = 8-amino-4-methyl-5-azaoct-3-en-2-one) have been synthesised and their molecular structures determined by X-ray crystallography. In complex 1, there is no inter-dimer H-bonding. However, complexes 2 and 3 form two different supramolecular structures in which the dinuclear entities are linked by strong H-bonds giving one-dimensional systems. Variable-temperature (300-2 K) magnetic susceptibility measurements and magnetization measurements at 2 K reveal that complexes and have antiferromagnetic coupling while has ferromagnetic coupling which is also confirmed by EPR spectra at 4-300 K. Magnetostructural correlations have been made taking into consideration both the azido bridging ligands and the existence of intermolecular hydrogen bonds in complexes 2 and 3.     

Proper forcing extensions and Solovay models

We study the preservation of the property of being a Solovay model under proper projective forcing extensions. We show that every strongly-proper forcing notion preserves this property. This yields that the consistency strength of the absoluteness of under strongly-proper forcing notions is that of the existence of an inaccessible cardinal. Further, the absoluteness of under projective strongly-proper forcing notions is consistent relative to the existence of a -Mahlo cardinal. We also show that the consistency strength of the absoluteness of under forcing extensions with -linked forcing notions is exactly that of the existence of a Mahlo cardinal, in contrast with the general ccc case, which requires a weakly-compact cardinal.Research partially supported by the research projects BFM2002-03236 of the Spanish Ministry of Science and Technology, and 2002SGR 00126 of the Generalitat de Catalunya. The second author was also partially supported by the research project GE01/HUM10, Grupos de excelencia, Principado de Asturias.Mathematics Subject Classification (2000): 03E15, 03E35