Synthesis of (Z)-tributylstannyl enynes: systematic studies of Sonogashira cross-coupling reactions between (E)-1-iodovinyl-1-tributylstannanes and terminal acetylenes using amines or tetrabutylammonium hydroxide (TBAOH) as activator

Sonogashira cross-coupling reactions involving (E)-iodo vinyl stannanes and terminal acetylenes were carried out in the presence of Pd(PPh₃)₄, CuI and several amines, affording (Z)-tributylstannyl enynes in moderate to good yields (62-91%). Utilizing the catalytic system containing Pd(PPh₃)₄ (5%), CuI (10%), and TBAOH (40% in aqueous media) as activator, better yields (72-91%) and lower reaction times were achieved.     

1‐(9H‐Carbazol‐4‐yloxy)‐3‐{[2‐(2‐methoxyphenoxy)ethyl]amino}propan‐2‐ol hemihydrate: a carvedilol solvatomorph

In the title racemic hemihydrated solvatomorph of carvedilol (carv), C₂₄H₂₆N₂O₄·0.5H₂O, the asymmetric unit contains two independent organic moieties and one water molecule. Within this 2(carv)·H₂O unit, the molecular components are strongly linked by hydrogen bonds and the unit acts as the basic building block for the crystal structure. Interactions parallel to (10) generate hydrogen‐bonded layers which are further linked by much weaker C—H...N/O interactions. The conformations of the organic molecules, as well as the hydrogen‐bonding interactions connecting them, are compared with other related structures in the literature.     

Conformations of diester triphenylphosphonium ylides with an ylidic ester or keto and ester ylidic groups

The structures of three related keto diester and diester ylides, namely diethyl 3‐oxo‐2‐(triphenylphosphoranylidene)glutarate, C₂₇H₂₇O₅P, (I), diethyl 3‐oxo‐2‐(triphenylphosphoranylidene)glutarate acetic acid monosolvate, C₂₇H₂₇O₅P·C₂H₄O₂, (II), and diethyl 2‐(triphenylphosphoranylidene)succinate, C₂₆H₂₇O₄P, (III), are presented. The syn‐keto anti‐ester conformations in the crystalline keto diesters are governed by electronic delocalization between the P—C and ylidic bonds and an acyl group, and by intra‐ and intermolecular interactions. There are also intramolecular attractive and repulsive interactions of different types (C—H...O and C—H...π) controlling the molecular conformations. The mono‐ylidic diester (III) has an anti‐ester conformation, while those for (I) and (II) are related to pyrolytic formation of acetylene derivatives. The terminal nonylidic ester group in (I) was disordered over two sets of almost equally populated positions.     

The web graph of a tourism system

The website network of a tourism destination is examined. Network theoretic metrics are used to gauge the static and dynamic characteristics of the webspace. The topology of the network is found partly similar to the one exhibited by similar systems. However, some differences are found, mainly due to the relatively poor connectivity and clusterisation of the network. These results are interpreted by considering the formation mechanisms and the connotation of the linkages between websites. Clustering and assortativity coefficients are proposed as quantitative estimations of the degree of collaboration and cooperation among destination stakeholders.     

High temperature Mössbauer studies of 57Fe: YSr2Cu3O7 related compounds containing oxyanions

Oxyanion substitutions at the copper sites can stabilize the Ba free phase YSr₂Cu₃O₇ and allow synthesis to occur under ambient conditions (P.R. Slater and C. Greaves, 1991; P.R. Slater et al., 1993). Here we report in situ ⁵⁷Fe Mössbauer spectroscopy experiments done in Y--Sr--Cu--O related oxides containing sulphate (SO₄ ^2-), phosphate (PO₄ ^3-) and borate (BO₃ ^3-), in the temperature range 300 K ? T ? 723 K. From the results obtained it has been possible to study the kinetics of oxygen loss, as well as the temperature dependence of the Fe species.