Hydrogen green

The second Heck reaction involves a naphthyl iodide (Ar2 = 2-naphthyl) but the initial mechanism is much the same. However, the enol ether has two diastereotopic faces syn or anti to the aromatic substituent (Ar1) introduced in the first step. Palladium is very sensitive to steric effects and generally forms less hindered complexes where possible. Thus coordination of the palladium(II) intermediate occurs on the face of the enol ether anti to Ar1. This in turn controls all the subsequent steps, which must be syn, leading to the trans product. The requirement for syn p-hydride elimination also explains the regiochemical preference of the elimination. In this cyclic structure there is only one hydrogen (green) that is syn the one on the carbon bearing the naphthyl substituent is anti to the palladium and cannot be eliminated.. ... 

Chloroform. (Gray=carbon, yef low=hydrogen, green=chlorine.j... 

Furikado I, Miyazawa T, Koso S, Shimao A, Kunimori K, Tomishige K (2007) Catalytic performance of Rh/Si02 catalysts in the glycerol reaction imder hydrogen. Green Chem 9 582-588... 

The way we produce H2 determines if it is green or black hydrogen. Green hydrogen refers to that obtained from renewable energy sources, like wind or solar,... 

Fig. 17.9 The molecular graphs of the following complexes (a) CsHe- HF, (b) C5H5 HF, (c) C4H4---HF, (d) CeHe- -HCCH, (e) CsHs - -HCCH and (t) CaHa- -HCCH. Big cirvles correspond to attractors (black - carbon, grey - hydrogen, green - fluorine) (Reprinted from Ref. [32] with kind permission of The American Chemical Society)...

Mikkola, J.-P., Virtanen, P., Karhu, H., Salmi, T., and Murzin, D.Y. (2006) Supported ionic liquids catalysts for fine chemicals citral hydrogenation. Green Chem., 8, 197-205. 

Furikado, L, Miyazawa, T., Koso, S., et al., 2007. Catalytic performance of Rh/SiOj in glycerol reaction imder hydrogen. Green Chemistry 9, 582-588. 

Musolino, M.G., Scarpino, L.A., MaurieUo, F., et al., 2009. Selective transfer hydrogenolysis of glycerol promoted by palladium catalysts in absence of hydrogen. Green Ghemistry 11,1511. 

---