Transition-Metal Catalysis of the Michael Reaction of 1,3-Dicarbonyl Compounds and Acceptor-Activated Alkenes

Michael additions catalyzed by transition metals and lanthanides species. A review. Part 1. Transition metals

“…Ytterbium triflate (Yb(OTf) 3 ) catalyzes Michael additions of ketoesters 52 (n = 2) to ethyl acrylate. 64a However, the authors report also that triflic acid is a more general catalyst.…”

“…The most general review by Christoffers was published in 1998. 3 More specific reviews published by the same author, 4a,b deal with the enantioselective construction of quaternary stereocenters, and still another review by Krause summarizes catalytic enantioselective Michael additions. 4c We present here a general review embracing all progress -synthetic, mechanistic, and stereochemical-reported since 1998.…”

“…The review by this author contains all pertinent information prior to 1998. 3 Further developments by this group are based on the use of hydrated iron(III) chloride (FeCl 3 .6H 2 O): (i) an intramolecular version between ketoesters and vinyl ketones (Entry 1); 11a (ii) the dimerization of 4 affording product 5 by the reaction of nucleophilic C-4 position of enol 4e with the electrophilic C-3 position of the keto tautomer 4k (Scheme 2 and Entry 2); 11b (iii) the use of quinones as electrophiles in the vinylogous Michael addition of 4 to 6 resulting in the formation of compounds of type 7 (Scheme 2 and Entry 3); 11c and (iv) the formation of polymers 10 by reaction of the bis-ketoester 8 with the bis-vinyl-ketone 9 (Scheme 2 and Entry 4). 11d A further development has been reported by Tkachev's group 12 Thus, Michael addition of ketoesters to oximes of unsaturated ketones affords pyridines (Scheme 2 and Entry 5).…”

“…Indeed, water increases in acidity when coordinated to metal. Those metals presenting lower pK (higher [H + ]) in the equation are the more active as catalysts in the studied reactions, A careful analysis of the reports in this review led us to at least three comments compatible with Spencer's analysis: (i) Christoffers states that, "Fe(acac) 3 34a Lanthanides have increased coordination numbers. This makes them ideal for simultaneous coordination of both reacting partners as well as ancillary chiral ligands around the metal.…”

Triethylamine and TBD supported on silica: useful heterogeneous catalysts for the reaction of β-dicarbonyl derivatives with α,β-unsaturated compounds under batch and continuous flow conditions

“…10 These reactions are usually performed in the presence of strong bases (i.e. alkali metal alkoxides and hydroxides), 11 transition metal complexes, 12 solid acids (i.e. alumina and clays), [13][14][15] …”