Enantioselective Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds

Enantioselective catalytic methods allowing the addition of both a nucleophile and an electrophile onto diazo compounds give a fast access into important building blocks. Herein, we report the highly enantioselective oxyalkynylation of diazo compounds using ethynylbenziodoxol-(on)e reagents and a simple copper bisoxazoline catalyst. The obtained a-benzoyloxy propargylic esters are useful building blocks, which are difficult to synthesize in enantiopure form using other methods. The obtained products could be efficiently transformed into vicinal diols and a-hydroxy propargylic esters without loss in enantiopurity

Copper-Catalyzed Oxy-Alkynylation of Diazo Compounds with Hypervalent Iodine Reagents

Alkynes have found widespread applications in synthetic chemistry, biology, and materials sciences. In recent years, methods based on electrophilic alkynylation with hypervalent iodine reagents have made acetylene synthesis more flexible and efficient, but they lead to the formation of one equivalent of an iodoarene as side-product. Herein, a more efficient strategy involving a copper-catalyzed oxy-alkynylation of diazo compounds with ethynylbenziodoxol(on)e (EBX) reagents is described, which proceeds with generation of nitrogen gas as the only waste. This reaction is remarkable for its broad scope in both EBX reagents and diazo compounds. In addition, vinyl diazo compounds gave enynes selectively as single geometric isomers. The functional groups introduced during the transformation served as easy handles to access useful building blocks for synthetic and medicinal chemistry

HYDROGEN FUELLED IC ENGINE – AN OVERVIEW

Hydrogen as a fuel in Internal Combustion engines is a solution for the near future to realize zero CO2 emissions for traffic applications. The hydrogen fuelled IC engine is ready for that. The storage and production of hydrogen, and to build the necessary infrastructure, are the real shortcomings in the general use of hydrogen in IC engines. This paper gives an overview of the development of hydrogen fuelled IC engines by the most important car manufactures (Ford, BMW etc.). This overview indicates the evolution in the development of hydrogen fuelled engines (different generation of engines). This evolution is also made at Ghent University. Ghent University has been working for nearly 15 years on the development and optimization of hydrogen engines. Several test rigs are in function (all with electronic control management systems and sequential multi-point injection)

Fast and Highly Chemoselective Alkynylation of Thiols with Hypervalent Iodine Reagents Enabled through a Low Energy Barrier Concerted Mechanism

Among all functional groups, alkynes occupy a privileged position in synthetic and medicinal chemistry, chemical biology, and materials science. Thioalkynes, in particular, are highly useful, as they combine the enhanced reactivity of the triple bond with a sulfur atom frequently encountered in bioactive compounds and materials. Nevertheless, general methods to access these compounds are lacking. In this article, we describe the mechanism and full scope of the alkynylation of thiols using ethynyl benziodoxolone (EBX) hypervalent iodine reagents. Computations led to the discovery of a new, three-atom concerted transition state with a very low energy barrier, which rationalizes the high reaction rate. On the basis of this result, the scope of the reaction was extended to the synthesis of aryl- and alkyl-substituted alkynes containing a broad range of functional groups. New sulfur nucleophiles such as thioglycosides, thioacids, and sodium hydrogen sulfide were also alkynylated successfully to lead to the most general and practical method yet reported for the synthesis of thioalkynes

Eosin Y Catalyzed Visible Light Oxidative C-C and C-P bond Formation

Eosin Y catalyzes efficiently the visible light mediated coupling of sp(3) C-H bonds adjacent to the nitrogen atom in tetrahydroisoquinoline derivatives in the absence of an external oxidant. Nitroalkanes, dialkyl malonates, malononitrile, and dialkyl phophonates were used as pronucleophiles in this metal-free, visible light oxidative coupling reaction

Metal-Free, Visible-Light-Mediated Direct C−H Arylation of Heteroarenes with Aryl Diazonium Salts

Visible light along with 1 mol % eosin Y catalyzes the direct C-H bond arylation of heteroarenes with aryl diazonium salts by a photoredox process. We have investigated the scope of the reaction for several aryl diazonium salts and heteroarenes. The general and easy procedure provides a transition-metal-free alternative for the formation of aryl-heteroaryl bonds

Visible-Light-Mediated α-Arylation of Enol Acetates Using Aryl Diazonium Salts

Visible light mediates efficiently the α-arylation of enol acetates by aryl diazonium salts under mild conditions using [Ru(bpy)(3)]Cl(2) as a photoredox catalyst. The broad scope of the reaction toward various diazonium salts and enol acetates was explored. The application of this reaction in the concise synthesis of 2-substituted indoles was demonstrated