Anthony R. Martin

Straightforward synthesis of [Au(NHC)X] (NHC = N-heterocyclic carbene, X = Cl, Br, I) complexes.

An improved protocol for the synthesis of [Au(NHC)X] (X = Cl, Br, I) complexes is reported. This versatile one-step synthetic methodology proceeds under mild conditions, in air, using technical grade solvents, is scalable and is applicable to a wide range of imidazolium and imidazolidinium salts.

Hydrophenoxylation of Alkynes by Cooperative Gold Catalysis

Over the past decade, the concept of cooperative or dual catalysis has emerged as an attractive and effective strategy to access unique reactivity and selectivity in synthetic organic chemistry. This type of catalysis has been shown in dual organo-catalyzed, organoand transition-metal-catalyzed, homobimetallic transition-metal-catalyzed and heterobimetallic catalyzed processes. Recently, it has also received increased attention in gold chemistry owing to the synthesis and isolation of dinuclear organogold species, such as gemdiaurated or s,p-diaurated acetylide complexes. These species were first proposed and later identified as key intermediates or catalyst reservoirs in gold-catalyzed reactions. We recently contributed to this area with the synthesis of dinuclear gold hydroxide species [{Au(NHC)}2(m-OH)][BF4] (1) (NHC = N-heterocyclic carbene), which can be easily prepared from commercially available [Au(NHC)(X)] (X = OH or Cl) complexes. Complexes 1 have been shown to be highly active catalysts for silverand acid-free goldcatalyzed transformations. We have also recently reported straightforward access to both gem-diaurated and s,p-diaurated acetylide species by reacting 1A (NHC = IPr = 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with aryl/vinyl boronic acids and terminal alkynes, respectively. In addition, complexes 1 exhibited particularly interesting catalytic properties. For example, during our studies of the goldcatalyzed nitrile hydration, the use of 1A afforded higher conversions to the desired amide than the gold monomer [Au(IPr)NTf2]. [8b] We have previously postulated that [{Au(NHC)}2(m-OH)][BF4] (1) could be considered as a combination of [Au(NHC)][BF4] (2) and [Au(NHC)(OH)] (3). [8] We believe that, under the appropriate reaction conditions, this equilibrium could be displaced, thus liberating a Lewis acid 2 and a Brønsted base 3 that could produce a synergistic effect leading to enhanced catalytic activity [Eq. (1)].

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

Summary The use of [Pd(NHC)(cinnamyl)Cl] precatalysts in the direct arylation of heterocycles has been investigated. Among four different precatalysts, [Pd(SIPr)(cinnamyl)Cl] proved to be the most efficient promoter of the reaction. The C–H functionalization of sulfur- or nitrogen-containing heterocycles has been achieved at low catalyst loadings. These catalyst charges range from 0.1 to 0.01 mol % palladium.

Persistent toxic substances in the Brazilian Amazon: contamination of man and the environment

The organochlorine insecticide DDT was extensively used in Brazil since 1945, both for agricultural purposes and for vector control measures. In 1986 its uses were forbidden in agriculture and in 1997 it was also phased-out in vector controls programs. However, the presence of DDT in urban and forested soils, breast milk and aquatic biota is still common, especially at the Amazon region. The results gathered since the middle of the 90s indicate that environmental contamination with this pesticide is still relatively high. Due to the high fish consumption by traditional riverside populations, human breast milk may represent an important source of DDT exposure to newborns. New results on DDT and PCBs in red dolphin (Inia geoffrensis), an endemic aquatic mammal of the Amazon region, is also reported.

Au]/[Pd] Multicatalytic processes: direct one-pot access to benzo[c]chromenes and benzo[b]furans

A new synthetic protocol that combines the advantages offered by eco-friendly solvent-free reactions and sequential transformations is reported. This strategy offers straightforward access to benzo[c]chromenes and benzo[b]furans from commercially available starting materials. This two-step, one-pot strategy consists of an Au-catalyzed hydrophenoxylation process followed by Pd-catalyzed C-H activation or Mizoroki-Heck reactions. The selectivity of the process towards C-H activation or Mizoroki-Heck reaction can be easily tuned.

Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes.

Summary Due to the synthetic advantages presented by the dual-gold-catalysed hydrophenoxylation of alkynes, a thorough study of this reaction was carried out in order to fully define the scope and limitations of the methodology. The protocol tolerates a wide range of functional groups, such as nitriles, ketones, esters, aldehydes, ketals, naphthyls, allyls or polyphenols, in a milder and more efficient manner than the previously reported methodologies. We have also identified that while we are able to use highly steric hindered phenols, small changes on the steric bulk of the alkynes have a dramatic effect on the reactivity. More importantly, we have observed that the use of substrates that facilitate the formation of diaurated species such as gem-diaurated or σ,π-digold–acetylide species, hinder the catalytic activity. Moreover, we have identified that the use of directing groups in unsymmetrical alkynes can help to achieve high regioselectivity in the hydrophenoxylation.

Both cetaceans in the Brazilian Amazon show sustained, profound population declines over two decades

Obligate river dolphins occur only in the rivers of Asia and South America, where they are increasingly subject to damaging pressures such as habitat degradation, food competition and entanglement in fishing gear as human populations expand. The Amazon basin hosts two, very different, dolphins—the boto or Amazon river dolphin (Inia geoffrensis) and the smaller tucuxi (Sotalia fluviatilis). Both species have wide geographical ranges and were once considered to be relatively abundant. Their IUCN Red List conservation status of Data Deficient (DD), due to limited information on threats, ecology, population numbers and trends, did not initially cause alarm. However, the development of dolphin hunting to provide fish bait at around the beginning of this millennium broadly coincided with the onset of a widespread perception that numbers of both species were in decline. Consequently, the need for population trend data to inform conservation advice and measures became urgent. This paper presents a 22-year time series of standardised surveys for both dolphins within the Mamirauá Reserve, Amazonas State, Brazil. Analysis of these data show that both species are in steep decline, with their populations halving every 10 years (botos) and 9 years (tucuxis) at current rates. These results are consistent with published, independent information on survival rates of botos in this area, which demonstrated a substantial drop in annual survival, commencing at around the year 2000. Mamirauá is a protected area, and is subject to fewer environmental pressures than elsewhere in the region, so there is no reason to suspect that the decline in dolphins within the Reserve is more pronounced than outside it. If South Americas freshwater cetaceans are to avoid following their Asian counterparts on the path to a perilous conservation status, effective conservation measures are required immediately. Enforcement of existing fishery laws would greatly assist in achieving this.

PRESUMED NORMAL ULTRASONOGRAPHIC FINDINGS OF THE TESTIS AND EPIDIDYMIS OF BOTOS (INIA GEOFFRENSIS)

Fifteen live adult male botos, or Amazon river dolphins (Inia geoffrensis), were examined using ultrasonography during the yearly capture expedition, between October and November 2005, at the Mamirauá Sustainable Development Reserve, within the Brazilian Amazon (3 degrees S, 65 degrees W). All examinations were performed with a Sonosite 180 plus ultrasound unit in conjunction with a 2- to 5-MHz multifrequency transducer convex array 180 Plus/Elite-C60. Age and maturity estimates were determined considering the body length, weight, and external characteristics. In all examinations, the testes were discerned by the presence of a hyperechoic central line, called the mediastinum testis, a landmark for their identification during ultrasonography. No significant differences in echogenicity were detected on the ultrasonographic appearance of the testes among the studied animals. On adult male botos, apparent parenchymal nodulation of the testis was observed on scanning in most of the animals and probably constituted evidence of reproductive maturity. Using the color Doppler technique, blood flow was detected along the mediastinum testis that progressively decreased toward the periphery of this organ. Little blood flow could be identified by color Doppler. Power Doppler allowed better accuracy to identify testicular vessels, their topography, and their differentiation from adjacent structures. Ultrasonographic examination provides useful data for morphologic characterization of the botos testes. Examination using Doppler techniques was considered a valuable tool to evidence blood flow through the testicular parenchyma.