A highly active diradical cobalt(<scp>iii</scp>) catalyst for the cycloisomerization of alkynoic acids
作者:Nicolas Leconte、Amaury du Moulinet d'Hardemare、Christian Philouze、Fabrice Thomas
DOI:10.1039/c8cc04459g
日期:——
The first cobalt-catalysed cycloisomerisation of alkynoicacids is reported, thanks to the design of a well-defined diradical cobalt(III) catalyst, in the absence of any additives. The high efficiency, regioselectivity and chemoselectivity are comparable to those of noble metal-based systems. The unique reactivity might be attributed to second coordination sphere effects.
Conjugate addition of potassiumtrifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol)