856324-72-6Relevant academic research and scientific papers
Fast ruthenium-catalysed allylation of thiols by using allyl alcohols as substrates
Zaitsev, Alexey B.,Caldwell, Helen F.,Pregosin, Paul S.,Veiros, Luis F.
scheme or table, p. 6468 - 6477 (2010/02/28)
The allylation of aromatic and aliphatic thiols, by using allyl alcohols as substrates, requires only minutes at ambient temperature with either a Ru Iv catalyst, [Ru(Cp*)(n3CH5)(CH 3CN)2](PF6)2 (2; Cp* = pentamethylcyclopentadienyl) or a combination of [Ru(Cp*)(CH 3CN)3](PF6) and camphor sulfonic acid. Quantitative conversion is normal and the catalyst possesses high functional-group tolerance. The use of [Ru(Cp*)(CH3CN) 3](PF6) alone affords poor results. A comparison is made to the results from catalytic runs based on the use of carbonates rather than alcohols, by using 2 as the catalyst, and it is shown that the products from the alcohols are formed faster, so there is no advantage in using a carbonate substrate. The observed branched-to-linear (b/1) ratios when using substituted alcohols decrease with time suggesting that the catalysts isomerise the products. A new methodology from which one can select the desired isomeric product is proposed. DFT calculations and NMR spectroscopic measurements, by using an arene sulfonic acid as co-catalyst, suggest that 6-complexes are not relevant for the catalytic system. Moreover, the DFT results indicate that l)any rf-complexes from the acids RC6H4SO 3H result from deprotonation of the acid, 2) complexation of the thiol, via the deprotonated sulfur atom, is preferred over complexation of the O atom of the sulfonate, RC6H4SO3and 3) a sulfonate O-atom complex will be difficult to detect.
