X-ray absorption study of the ferromagnetic Cu moment at the YBa_(2)Cu_(3)O_(7)/La_(2/3)Ca_(1/3)MnO_(3) interface and variation of its exchange interaction with the Mn moment

With x-ray absorption spectroscopy and polarized neutron reflectometry we studied how the magnetic proximity effect at the interface between the cuprate high-TC superconductor YBa_(2)Cu_(3)O_(7) (YBCO) and the ferromagnet La_(2/3)Ca_(1/3)MnO_(3) (LCMO) is related to the electronic and magnetic properties of the LCMO layers. In particular, we explored how the magnitude of the ferromagnetic Cu moment on the YBCO side depends on the strength of the antiferromagnetic (AF) exchange coupling with the Mn moment on the LCMO side. We found that the Cu moment remains sizable if the AF coupling with the Mn moments is strongly reduced or even entirely suppressed. The ferromagnetic order of the Cu moments thus seems to be intrinsic to the interfacial CuO_(2) planes and related to a weakly ferromagnetic intraplanar exchange interaction. The latter is discussed in terms of the partial occupation of the Cu 3d_(3z^(2)−r^(2)) orbitals, which occurs in the context of the so-called orbital reconstruction of the interfacial Cu ions.

Adición conjugada de compuestos 1,3-dicarbonílicos a maleimidas catalizada por 2-aminobencimidazoles quirales

En la presente memoria se describe la síntesis y aplicación de diversos organocatalizadores quirates derivados de 2-aminobencimidazol en reacciones de adición Michael de compuestos 1,3-discarbonílicos a maleimidas. En este trabajo se ha preparado un organocatalizador quiral y reciclable con simetría C₂ derivado de bencimidazol y (1R,2R)-ciclohexano-1,2-diamina y se ha utilizado con éxito en la adición conjugada de β-dicetonas, β-cetoésteres y malonatos de dialquilo a maleimida y maleimidas N-sustituidas. La adición, que se lleva cabo en tolueno y a temperatura ambiente, conduce a las correspondientes succinimidas quirales con buenos rendimientos, moderadas diastereoselectividades y excelentes excesos enantioméricos. También se han realizado estudios mecanísticos mediante cálculos computacionales DFT y estudios de difusión por resonancia magnética nuclear para determinar el modo de actuación del catalizador y el estado de transición de la reacción de adición conjugada de compuestos 1,3-dicarbonílicos a maleimidas que han confirmado el estado de transición y mecanismo propuestos.

Domino 1,3-Dipolar Cycloadditions of N-Alkyl-α-Amino Esters with Paraformaldehyde: A Direct Access to α-Hydroxymethyl α-Amino Acids

N-Alkyl-α-amino esters undergo a domino reaction, based on the iminium cation generation, with paraformaldehyde, followed by a 1,3-dipolar cycloaddition of the stabilized azometh­ine ylide with another equivalent of formaldehyde. The resulting products are oxazolidines, which can be transformed after hydrolysis into α-hydroxymethyl α-amino acid or its derivatives. The diastereoselective 1,3-dipolar cycloaddition was performed using sarcosine (–)-menthyl or (–)-8-phenylmenthyl esters affording the cyclic product with moderate enantiomeric ratio.

Enantioselective Synthesis of Succinimides by Michael Addition of 1,3-Dicarbonyl Compounds to Maleimides Catalyzed by a Chiral Bis(2-aminobenzimidazole) Organocatalyst

A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.

Nuevos precursores de iluros de azometino para cicloadiciones 1,3-dipolares

En la presente memoria se describe la síntesis de derivados de pirrolidina, pirrolizidina e indolizidina mediante diferentes metodologías que involicruan una cicloadición 1,3-dipolar multicomponente a través de iluros de azometino generados in situ, así como el estudio cinético de esta reacción vía dos componentes. En el Capítulo I, se describen diferentes métodos de estudio cinético para la interpretación y obtención de parámetros mecanísticos de dicha reacción a partir de la información obtenida mediante Análisis Térmico y más concretamente calorimetría diferencial de barrido. En el Capítulo II, dividido en tres partes, se describe la síntesis de pirrolidinas mediante cicloadición 1,3-dipolar multicomponente (a partir de iluros de azometino) térmica y por irradiación por microondas (Parte 1), catalizada por plata(I) (Parte II) y asimétrica mediante catálisis por plata(I) y un ligando quiral (Parte III); así como la posible aplicabilidad en la síntesis de productos naturales o que presenten actividad biológica. En el Capítulo III, se describe la síntesis de pirrolizidinas mediante la cicloadición 1,3-dipolar multicomponente con iluros de azometino con y sin uso de sales de plata(I), así como un ejemplo en la construcción de un esqueleto de indolizidina siguiendo la misma metodología. Finalmente se incluyen las conclusiones junto con otro tipo de anexos como son las referencias, abreviaciones y la biografía.

1,3-Dipolar cycloadditions of azomethine imines

Azomethine imines are considered 1,3-dipoles of the aza-allyl type which are transient intermediates and should be generated in situ but can also be stable and isolable compounds. They react with electron-rich and electron-poor olefins as well as with acetylenic compounds and allenoates mainly by a [3 + 2] cycloaddition but they can also take part in [3 + 3], [4 + 3], [3 + 2 + 2] and [5 + 3] with different dipolarophiles. These 1,3-dipolar cycloadditions (1,3-DC) can be performed not only under thermal or microwave conditions but also using metallo- and organocatalytic systems. In recent years enantiocatalyzed 1,3-dipolar cycloadditions have been extensively considered and applied to the synthesis of a great variety of dinitrogenated heterocycles with biological activity. Acyclic azomethine imines derived from mono and disubstituted hydrazones could be generated by prototropy under heating or by using Lewis or Brønsted acids to give, after [3 + 2] cycloadditions, pyrazolidines and pyrazolines. Cyclic azomethine imines, incorporating a C–N bond in a ring, such as isoquinolinium imides are the most widely used dipoles in normal and inverse-electron demand 1,3-DC allowing the synthesis of tetrahydro-, dihydro- and unsaturated pyrazolo[1,5-a]isoquinolines in racemic and enantioenriched forms with interesting biological activity. Pyridinium and quinolinium imides give the corresponding pyrazolopyridines and indazolo[3,2-a]isoquinolines, respectively. In the case of cyclic azomethine imines with an N–N bond incorporated into a ring, N-alkylidene-3-oxo-pyrazolidinium ylides are the most popular stable and isolated dipoles able to form dinitrogen-fused saturated and unsaturated pyrazolopyrazolones as racemic or enantiomerically enriched compounds present in many pharmaceuticals, agrochemicals and other useful chemicals.

Regio and diastereoselective multicomponent 1,3-dipolar cycloadditions between prolinate hydrochlorides, aldehydes and dipolarophiles for the direct synthesis of pyrrolizidines

A general synthesis of highly substituted pyrrolizidines can be performed by a multicomponent 1,3-dipolar cycloaddition using proline ester hydrochlorides, aldehydes and dipolarophiles, at room temperature without catalysts or in the presence of AgOAc (5 mol %). In the case of (2S,4R)-4-hydroxyproline derivatives it is possible to obtain enantioenriched pyrrolizidines with high control of the regio- and diastereoselectivity affording the adducts 2,4-trans-2,5-trans according to an endo-approach and a S-dipole geometry of the in situ generated azomethine ylide. For proline esters a similar regioselectivity and endo-diastereoselectivity are observed when the dipole promotes an α-attack. However, when ethyl glyoxylate is used as aldehyde component the γ-attack of the S-ylide takes place preferentially giving rise the opposite regioselectivity for acrylic dipolarophiles, being crucial the role of silver acetate. In this case, the exo-adducts with a 2,3-cis-2,5-trans relative configuration are diastereoselectively obtained. In addition, computational studies have also been carried out to shed light on the origins of the diastereo- and regioselectivity observed for the described 1,3-dipolar cycloadditions.

2-Aminobenzimidazole Organocatalyzed Asymmetric Amination of Cyclic 1,3-Dicarbonyl Compounds

The use of a trans-cyclohexanediamine benzimidazole derivative as a hydrogen-bond catalyst for the electrophilic amination of cyclic 1,3-dicarbonyl compounds is herein presented. High yields and enantioselectivities varying from moderate to excellent are generally obtained using mild reaction conditions and as low as 1 mol% of catalyst loading.

Quitclaim, 1745/6 March 1

Handwritten quitclaim by Grace Dean as beneficiary of the estate of Benjamin Wadsworth, acknowledging payment by Andrew Bordman.

Jamaica, 1763 (Image 2 of 4) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: This map of the island of Jamaica; laid down from the papers and under the direction of Henry Moore, Esqr.; His Majesty's Lieutenant Governor and Commander in Chief of that island, in the years 1756, 57, 58, 59, 60 & 61; & from a great number of actual surveys performed by the publishers is humbly inscribed by his lordship's most obedient & most humble servants, Thos. Craskell, engineer, Jas. Simpson, surveyor. It was published by D. Fournier in 1763. Scale [ca 1:200,000]. This layer is image 2 of 4 total images of the four sheet map, representing the southeast portion of the map. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Jamaica Grid projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as towns, villages, and other human settlements, roads, drainage, selected buildings, ground cover, shoreline features, and more. Relief shown pictorially. Includes also illustrations.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.

County of Cornwall, Jamaica, 1763 (Image 2 of 4) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: This map of the county of Cornwall, in the island of Jamaica; laid down from the papers, under the direction of, Henry Moore, Esqr., His Majesty's Lieutenant Governor, and Commander in Chief of that island, in the years 1756, 57, 58, 59, 60 & 61, & from a great number of actual surveys performed by the publishers is humbly inscribed by his lordship's most obedient & humble servants, Thos. Craskell, engineer, Jas. Simpson, surveyor. It was published by D. Fournier in 1763. Scale [ca. 1:95,000]. This layer is image 2 of 4 total images of the four sheet source map, representing the southeast portion of the map. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Jamaica Grid projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as towns, villages, and other human settlements, roads, parish boundaries, drainage, selected buildings and names of landowners, ground cover, shoreline features, shoals, channels, anchorage points, and more.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.

County of Middlesex, Jamaica, 1763 (Image 2 of 4) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: This map of the county of Middlesex in the island of Jamaica; laid down from the papers, and under the direction of Henry Moore, Esqr., His Majesty's Lieutenant Governor and Commander in Chief of that island, in the years 1756, 57, 58, 60, & 61 and from a great number of actual surveys performed by the publishers is humbly inscribed by his lordship's most obedient & most humble servants, Thos. Craskell, engineer, Jas. Simpson, surveyor. It was published by D. Fournier in 1763. Scale [ca. 1:95,000]. The layer is image 2 of 4 total images of the four sheet map, representing the southwest portion of the map. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Jamaica Grid projected coordinate system. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as towns, villages, and other human settlements, roads, parish boundaries, drainage, selected buildings and names of landowners, ground cover, shoreline features, shoals, channels, anchorage points, and more.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.