Highly substituted 4H-pyrans can be smoothly synthesized from readily available 2-(1-alkynyl)-2-alkene-1-ones by DBU- or n-Bu(3)P catalyzed hetero-[4+2] cycloaddition reactions, in which 2-(1-alkynyl)-2-alkene-1-ones act as both heterodiene and heterodinenophile.

A series of complexes of novel chelating thione-alkene S(η(2)-C[double bond, length as m-dash]C)S tridentate ligands bound to late transition metals (Ir, Rh, Pd) were isolated and characterised. Counter-anions play an important role in the binding of the alkene moiety to the metals. Different solvents were observed to affect the stability of the rhodium complexes.

Simple strategies for using alkene reductase enzymes to produce gram-scale quantities of both (R)- and (S)-citronellal have been developed. The methodology is easily accessible to non-specialist laboratories, allowing alkene reductases to be added to the toolbox of routine synthetic transformations.

A new method for the synthesis of tricyclic nitrogen heterocycles from N,2-diallylaniline derivatives is described. These transformations proceed via sequential alkene aminopalladation of an intermediate L(n)Pd(Ar)(NRR') species followed by alkene carbopalladation of the resulting L(n)Pd(Ar)(R) complex. Both alkene insertion steps occur in preference to C-N or C-C bond-forming reductive elimina...

The biochemistry of the violaxanthin cycle in relationship to photosynthesis is reviewed. The cycle is a component of the thylakoid and consists of a reaction sequence in which violaxanthin is converted to zeaxanthin (de—epoxidation) and then regenerated (epoxidation) through separate reaction mechanisms. The arrangement of the cycle in the thyla— koid is transmembranous with the de—epoxidation...

Catalytic aerobic dehydrogenation of organic substrates is going through a Renaissance. Recent advances in this area have led to the discovery of palladium-catalyzed alcohol dehydrogenations and oxidative heteroand carbocyclizations. The development of asymmetric catalytic dehydrogenations is the latest advance in a long line of catalytic asymmetric oxidation reactions. Introduction Asymmetric ...

effects of imidazoles and substituted pyridines and pure s-donors on the oxidation of cyclooctene with naio4 by 5,10,15,20-tetraphenylporphyrinato-manganese(iii) acetate, mn(tpp)oac, and 5,10,15,20-tetramesitylporphyrinato-manganese(iii) acetate, mn(tmp)oac, catalysts in ch2cl2-h2o solvent are studied. coordination of the nitrogen donors to the mn-catalysts generally caused a reduction in the e...

To isolate secondary organic aerosol (SOA) formation in ozone-alkene systems from the additional influence of hydroxyl (OH) radicals formed in the gas-phase ozone-alkene reaction, OH scavengers are employed. The detailed chemistry associated with three different scavengers (cyclohexane, 2-butanol, and CO) is studied in relation to the effects of the scavengers on observed SOA yields in the ozon...