131029-02-2Relevant articles and documents
Broad Scope Synthesis of Ester Precursors of Nonfunctionalized Chiral Alcohols Based on the Asymmetric Hydrogenation of α,β-Dialkyl-, α,β-Diaryl-, and α-Alkyl-β-aryl-vinyl Esters
León, Félix,González-Liste, Pedro J.,García-Garrido, Sergio E.,Arribas, Inmaculada,Rubio, Miguel,Cadierno, Victorio,Pizzano, Antonio
, p. 5852 - 5867 (2017/06/07)
The catalytic asymmetric hydrogenation of trisubstituted enol esters using Rh catalysts bearing chiral phosphine-phosphite ligands (P-OP) has been studied. Substrates covered comprise α,β-dialkyl, α-alkyl-β-aryl, and α,β-diarylvinyl esters, the corresponding hydrogenation products being suitable precursors to prepare synthetically relevant chiral nonfunctionalized alcohols. A comparison of reactivity indicates that it decreases in the order: α,β-dialkyl > α-alkyl-β-aryl > α,β-diaryl. Based on the highly modular structure of P-OP ligands employed, catalyst screening identified highly enantioselective catalysts for α,β-dialkyl (95-99% ee) and nearly all of α-alkyl-β-aryl substrates (92-98% ee), with the exception of α-cyclohexyl-β-phenylvinyl acetate which exhibited a low enantioselectivity (47% ee). Finally, α,β-diarylvinyl substrates showed somewhat lower enantioselectivities (79-92% ee). In addition, some of the catalysts provided a high enantioselectivity in the hydrogenation of E/Z mixtures (ca. Z/E = 75:25) of α,β-dialkylvinyl substrates, while a dramatic decrease on enantioselectivity was observed in the case of α-methyl-β-anisylvinyl acetate (Z/E = 58:42). Complementary deuteration reactions are in accord with a highly enantioselective hydrogenation for both olefin isomers in the case of α,β-dialkylvinyl esters. In contrast, deuteration shows a complex behavior for α-methyl-β-anisylvinyl acetate derived from the participation of the E isomer in the reaction.
DIRECT ANTI-MARKOVNIKOV ADDITION OF ACIDS TO ALKENES
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Page/Page column 2; 14; 15, (2013/12/03)
A method of making an anti-Markovnikov addition product is carried out by reacting an acid with an alkene or alkyne in a dual catalyst reaction system to the exclusion of oxygen to produce said anti-Markovnikov addition product; the dual catalyst reaction system comprising a single electron oxidation catalyst in combination with a hydrogen atom donor catalyst. Compositions useful for carrying out such methods are also described.
A new enzymatic approach to (R)-Tamsulosin hydrochloride
Acetti, Daniela,Brenna, Elisabetta,Fuganti, Claudio
, p. 488 - 492 (2007/10/03)
An enantioselective baker's yeast mediated approach to the pharmacologically active (R)-enantiomer of Tamsulosin hydrochloride is reported.