Activation of Imines by Rare Earth Metal Triflates. Ln(OTf)3- or Sc(OTf)3-Catalyzed Reactions of Imines with Silyl Enolates and Diels-Alder Reactions of Imines

Scandium Triflate in Organic Synthesis

“…The yield was improved when Sc(OTf) 3 was used N-benzylhydroxylamine, and N-phenylmaleimide proceeded instead of Yb(OTf) 3 as a catalyst (Equation 17). [43] Not smoothly in the presence of a catalytic amount of a only silyl enolates derived from esters, but also one derived Sc(OTf) 3 , to afford the corresponding isoxazolidine deriva-from a thioester worked well to give the desired β-amino tive in a good yield with a high diastereoselectivity (Equa-esters and thioester with high yields. In the reactions of the tion 15).…”

Lanthanide Complexes of the Monovacant Dawson Polyoxotungstate [α1‐P2W17O61]10− as Selective and Recoverable Lewis Acid Catalysts

“…We first examined Mannich-type reactions of silyl enol ethers with imines [35,36] and found that no reaction occurred with the potassium salts of the POM-Ln complexes, possibly due to solubility issues. We thus switched to complexes that are soluble in organic solvents, [30] especially acetonitrile, and were able to isolate b-amino ketones 1 a-e, thus proving the catalytic activity of the POM-Ln complexes, although the reaction times were generally longer than those observed with the corresponding lanthanide triflates (two days vs. a few hours).…”

Lewis Base Catalyzed Mannich‐Type Reactions between Trimethylsilyl Enol Ethers and Aldimines

“…In general, Mannichtype reactions proceed via the electrophilic activation step of Mannich acceptor with Lewis acids. Ojima et al first reported in 1977 that the Mannich-type reaction between benzylideneaniline and silyl ketene acetal was accelerated by using stoichiometric amounts of TiCl 4 . [1] After this report, various Lewis acid-mediated Mannich-type reactions have been developed.…”

“…However, there is a successful Mannich-type reaction reported by Kobayashi et al using a catalytic amount of Lewis acid such as scandium trifluoromethanesulfonate or lanthanoid trifluoromethanesulfonate in 1995. [4] Recently, enantioselective Mannich-type reaction using chiral Lewis acid has been studied intensively.…”

“…[11] Results and Discussion Nitrogen anions generated from amides or imides-catalyzed Mannich-type reaction between N-tosylaldimine and trimethylsilyl enol ethers in DMF: In the first place, a reaction between N-tosylaldimine 1 a and TMS enol ether 2 a by using 10 mol % lithium pyrrolidone (4) at À45 8C in DMF was investigated as a model, and the corresponding b-amino ester 3 aa [12] was obtained in 37 % yield (Scheme 1).…”