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The sulfur oxide (SO x ) concentrations during oxy-fuel combustion are generally higher compared to conventional air firing. The higher SO x concentrations, particularly sulfur trioxide (SO 3 ) in combination with high concentration of water in the recycled flue gas, increase the sulfuric acid dew point temperature in oxy-fuel fired systems, thereby increasing allowable flue gas temperatures and reducing the thermal efficiency of a power plant. This paper presents results of experiments carried out at a 20 kW once-through combustion rig of the Institute of Combustion and Power Plant Technology (IFK) of the University of Stuttgart simulating different extents of oxy-fuel recycle gas cleaning by impurities injection to the oxidant gas of a once-through combustion reactor. Three Australian coals that have previously been tested under air and oxy-fuel conditions at the Aioi furnace of IHI in Japan were used in the experiments. The SO x emissions were measured, conversion ratios of sulfur dioxide (SO 2 ) to SO 3 were calculated, and results were compared with existing literature, finding good agreement. The experiments with different extents of recycle gas cleaning and therefore different SO 2 levels in the system, revealed differences in the SO 3 generation behavior: A coal-specific trend of increasing conversion ratios of SO 2 to SO 3 with increased flue gas SO 2 levels was observed that could be related to the ash composition of the three different coals. The capture of SO x in a baghouse filter was also evaluated. Acid dew point temperatures (ADPs) for the flue gas were calculated for the various firing conditions. Acid dew point (ADP) temperatures increased by up to 50 °C when changing from air to oxy-firing with recycling of H 2 O and SO 2 . Considerable differences in the ADPs were found for different extents of oxy-fuel recycle gas treatment and were evaluated in respect to power plant efficiency implications.

Bicyclobutanes are among the most highly strained isolable organic compounds and their associated low activation barriers to reactivity make them intriguing building-blocks in organic chemistry. In recent years, numerous creative synthetic strategies exploiting their heightened reactivity have been presented and these discoveries have often gone hand-in-hand with the development of more practical routes for their synthesis. Their proclivity as strain-release reagents through their weak central C–C bond has been harnessed in a variety of addition, rearrangement and insertion reactions, providing rapid access to a rich tapestry of complex molecular scaffolds. This review will provide an overview of the different options available for bicyclobutane synthesis, the main classes of compounds that can be prepared from bicyclobutanes, and the associated modes of reactivity used.

The design and a gram-scale synthesis of a bench-stable cyclohexa-1,4-diene-based surrogate of gaseous hydrogen iodide are described. By initiation with a moderately strong Brønsted acid, hydrogen iodide is transferred from the surrogate onto C−C multiple bonds such as alkynes and allenes without the involvement of free hydrogen iodide. The surrogate fragments into toluene and ethylene, easy-to-remove volatile waste. This hydroiodination reaction avoids precarious handling of hydrogen iodide or hydroiodic acid. By this, a broad range of previously unknown or difficult-to-prepare vinyl iodides can be accessed in stereocontrolled fashion.

A short (10 step) and efficient (15% overall yield) synthesis of the natural product (-)-(3 R)-inthomycin C is reported. The key steps comprise three C-C bond-forming reactions: (i) a vinylogous Mukaiyama aldol, (ii) an olefin cross-metathesis reaction, and (iii) an asymmetric Mukaiyama-Kiyooka aldol. This route is notable for its brevity and has the advantage of lacking stoichiometric tin-promoted cross-coupling reactions present in previous approaches. Initial investigations on the biological activity of (-)-(3 R)-inthomycin C and structural analogues on human cancer cell lines are also described for the first time.

A regioselective hydrodeuteration of alkenes using monodeuterated cyclohexa-1,4-dienes as surrogates for hydrogen deuteride (HD) gas is reported. The metal-free process proceeds under B(C 6 F 5 ) 3 catalysis presumably by deuteride abstraction to form borodeuteride [DB(C 6 F 5 ) 3 ] − and highly Brønsted-acidic Wheland intermediates. Low catalyst loadings (2.5 mol %) are used, and the reaction proceeds at room temperature.

A current research program in our laboratory is devoted to the development of cyclohexa-1,4-diene-based surrogates of difficult-to-handle compounds and their application in metal-free ionic transfer reactions. These investigations grew from our interest in silylium ion chemistry and consequently concentrated initially on surrogates of gaseous and explosive hydrosilanes such as Me3SiH and even monosilane (SiH4). Since then, we have expanded the concept to design surrogates of other species including H2, mineral acids (HI and HBr), and hydrocarbons (isobutane and isobutene). This Account summarizes our discoveries in this area to date, describing the challenges we faced along the way and how we combatted them.1 Introduction2 Transfer Hydrofunctionalization: Variation of the Electrofuge3 Transfer Hydrofunctionalization: Variation of the Nucleofuge4 Transfer Hydrohalogenation Using a Modified Surrogate5 Surrogate Synthesis6 Conclusion

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