Gold catalysis: on the phenol synthesis.

[reaction--see text] For the gold-catalyzed phenol synthesis an intramolecular migration of the oxygen atom was proven. Several other late transition metals with d(8) configuration allow this conversion, providing evidence for Au(III) being a catalytically active species. On the other hand gold was still the most active catalyst and gives the cleanest conversion. With additional alkynyl substituents another ring could be closed to provide doubly annellated arenes.

Two isomorphous benzenesulfonamide crystal structures determined by intermolecular C-H...O, C-H...pi and C-H...Cl interactions.

The title compounds, N-[5-(4-chlorophenyl)furan-2-ylmethyl]-4-methyl-N-(prop-2-ynyl)benzenesulfonamide, (Ia), and N-[5-(2-chlorophenyl)furan-2-ylmethyl]-4-methyl-N-(prop-2-ynyl)benzenesulfonamide, (Ib), both C(21)H(18)ClNO(3)S, have isomorphous crystal structures. The crystal packing is mainly determined by intermolecular C-H...O and C-H...pi interactions. These interactions are very similar in (Ia) and (Ib). Additional intermolecular C-H...Cl interactions appear less important and are different in (Ia) and (Ib). The different positions of the Cl atoms result in small variations of the crystal packing of the two compounds.

Complex biological responses to the experimental acidification of Little Rock Lake, Wisconsin, USA.

Acidification can affect aquatic organisms directly through hydrogen ion toxicity, and indirectly through disrupted food web dynamics and altered abiotic conditions. Field populations from selected taxa were studied during the Little Rock Lake whole-basin acidification experiment to illustrate patterns whose timing suggests direct (i.e. immediate) or indirect (i.e. delayed or non-uniform) responses to pH change. As the treatment basin was acidified to pH 5.6, 5.2 and 4.7, immediate changes consistent with a direct pH response were observed for species representing several trophic levels. For other taxa (e.g. littoral invertebrates associated with filamentous algal mats, several species of pelagic zooplankton), indirect mechanisms induced by food web changes were more likely explanations for abundance patterns. The results presented here suggest that the responses of aquatic ecosystems to acidification involve a complex interplay between direct pH effects and subsequent indirect interactions.