The selective 1,2-aminoacylation of olefins provides opportunities for the rapid construction of nitrogen-containing molecules. However, the lack of CO-free acylation reactions has limited their ...application. By using photoredox proton-coupled electron transfer (PCET)/Ni dual-catalysis, a highly regio- and diastereoselective amidoacylation of unactivated olefins has been developed. Various acyl electrophiles are compatible, including alkyl- and aryl acyl chlorides and anhydrides, as well as in situ activated carboxylic acids. Hammett studies and other mechanistic experiments to elucidate features of the diastereoselectivity, a transient absorption study of the PCET step, as well as computational evidence, provide an in-depth understanding of the disclosed transformation.
A highly effective method for derivatizing 2,1-borazaronaphthalene cores using ammonium alkylbis(catecholato)silicates via photoredox/nickel dual catalysis is reported. By forging Csp 3–Csp 2 bonds ...via this approach, alkyl fragments with various functional groups can be introduced to the azaborine core, affording previously inaccessible heterocyclic isosteres in good to excellent yields. The base-free, room-temperature conditions outlined allow sensitive functional group tolerance, even permitting the cross-coupling of unprotected primary and secondary amines.
Among aromatic compounds, borazarenes represent a significant class of isosteres in which carbon‐carbon bonds have been replaced by B−N bonds. Described herein is a summary of the selective reactions ...that have been developed for known systems, as well as a summary of computationally‐based predictions of selectivities that might be anticipated in reactions of yet unrealized substructures.
Effects of land use changes are starting to be included in estimates of life-cycle greenhouse gas (GHG) emissions, so-called carbon footprints (CFs), from food production. Their omission can lead to ...serious underestimates, particularly for meat. Here we estimate emissions from the conversion of forest to pasture in the Legal Amazon Region (LAR) of Brazil and present a model to distribute the emissions from deforestation over products and time subsequent to the land use change. Expansion of cattle ranching for beef production is a major cause of deforestation in the LAR. The carbon footprint of beef produced on newly deforested land is estimated at more than 700 kg CO2-equivalents per kg carcass weight if direct land use emissions are annualized over 20 years. This is orders of magnitude larger than the figure for beef production on established pasture on non-deforested land. While Brazilian beef exports have originated mainly from areas outside the LAR, i.e. from regions not subject to recent deforestation, we argue that increased production for export has been the key driver of the pasture expansion and deforestation in the LAR during the past decade and this should be reflected in the carbon footprint attributed to beef exports. We conclude that carbon footprint standards must include the more extended effects of land use changes to avoid giving misleading information to policy makers, retailers, and consumers.
The use of bis-boronic acid for the direct synthesis of boronic acids has greatly facilitated the two-step, one-pot borylation/Suzuki cross-coupling reaction between aryl and heteroaryl halides. With ...use of Buchwald's second-generation XPhos preformed catalyst, high yields of cross-coupled products were obtained for most substrates. The method also allows an efficient two-step, one-pot synthesis, providing access to three distinct cross-coupled products after column chromatography. The method also provides a rapid and convenient route to teraryl compounds.
Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if “unacceptable global change” is to be avoided. Chemical pollution ...was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical's life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social approaches to mitigate global chemical pollution that emphasize a preventative approach; coordinate pollution control and sustainability efforts; and facilitate implementation of multiple (and potentially decentralized) control efforts involving scientists, civil society, government, non-governmental organizations and international bodies.
•Planetary boundaries of Rockström et al. (2009) to avoid “unacceptable global change”•Boundary for chemical pollution (PBCP) reflects Earth's finite assimilative capacity.•While conceptually necessary, a PBCP is challenging to operationalize.•To meet the need of abating global pollution, four recommendations are presented.•Recommend devising new, preventative technologies and social approaches.
To assess the prevalence of urinary incontinence and its influence on the quality of life.
A random sample of every fourth woman aged > or =20 years resident in a primary health care district of the ...city of Göteborg was obtained from the population register (n=2911). The women were invited by letter to complete a questionnaire concerning urinary incontinence. The women were also requested to assess their quality of life using a visual analogue scale.
The overall response rate was 77%. The prevalence of urinary incontinence increased (p<0.001) in a linear fashion from 3% in the cohort 20-29 years to 32 % in the cohort of women aged > or =80 years. The proportion of women suffering from stress incontinence decreased (p<0.001) with increasing age, while the proportion of women suffering from urge and mixed incontinence increased (p<0.01) with increasing age. Women with stress incontinence had a greater body weight and had given birth to a greater number of children compared to continent women. There was, however, in this respect no difference between women with urge incontinence and continent women. Women with urinary incontinence reported a poorer quality of life compared to continent women (p<0.01). Women with urge incontinence and women with mixed incontinence reported a poorer quality of life compared to women with stress incontinence (p<0.05). Only 6% of the women from this population had sought medical attention for urinary incontinence.
Although urinary incontinence was a prevalent condition, particularly among the elderly and had a negative influence on the quality of life, only a small number of women had sought medical care.
The Suzuki-Miyaura reaction has become one of the more useful tools for synthetic organic chemists. Until recently, there did not exist a direct way to make the most important component in the ...coupling reaction, namely the boronic acid. Current methods to make boronic acids often employ harsh or wasteful reagents to prepare boronic acid derivatives and require additional steps to afford the desired boronic acid. The scope of the previously reported palladium-catalyzed, direct boronic acid synthesis is unveiled, which includes a wide array of synthetically useful aryl electrophiles. It makes use of the newly available second generation Buchwald XPhos preformed palladium catalyst and bis-boronic acid. For ease of isolation and to preserve the often sensitive C–B bond, all boronic acids were readily converted to their more stable trifluoroborate counterparts.
The carbonylative Suzuki–Miyaura reaction between aryl bromides and arylboronic acid equivalents is herein reported, using base-free conditions and a limited excess of carbon monoxide generated ex ...situ from stable CO-precursors. Under these conditions, unsymmetrical biaryl ketones were obtained in modest to excellent yields. This method was adapted to the synthesis of the triglyceride and cholesterol regulator drug, fenofibrate, and its 13C-labeled derivative in good yields from the appropriate CO-precursor.
The azaborine motif provides a mimic of aromatic systems through replacement of a C═C bond with a B-N bond. In particular, 2,1-borazaronaphthalenes, accessible through robust methods of synthesis and ...subsequent functionalization, afford an ideal platform to use for a variety of applications. However, the scope of substructures for this archetype has been limited by the lack of nitrogen-containing heteroaryls that can be incorporated within them. In this study, modified reaction conditions were developed to provide access to a wider range of substructures.
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