Chiral bis(oxazoline)–copper complex catalyzed Diels–Alder reaction in ionic liquids: remarkable reactivity and selectivity enhancement, and efficient recycling of the catalyst

Room-Temperature Ionic Liquids: Solvents for Synthesis and Catalysis. 2

“…Chiral C 2 -symmetric bis(oxazoline)−copper {BOX−Cu} complexes have been used as catalysts for Diels−Alder reactions in ionic liquids. When the IndaBOX−Cu-catalyzed reaction of cyclopentadiene with 3-acryloyloxazolidin-2-one (Scheme ) was conducted in [C 4 C 1 im]X {X = [BF 4 ], [OTf], [PF 6 ], or [SbF 6 ]}, it was faster and more selective when the less basic anions were used . It was proposed that this was the result of the elevated water levels in the hydrophilic ionic liquids, which were not predried before the reactions.…”

Copper-Catalyzed Diels−Alder Reactions

“…67 Recently, Kim et al reported that the Diels-Alder reaction of 18 with 33 was efficiently catalyzed by (1S,2R)-IXa/ Cu(OTf) 2 in [Bmim]SbF 6 (Bmim ) 1-N-butyl-3-methylimidazolium) even at low catalytic loading (0.6 mol %). 114 Under these conditions, endo-47 (dr ) 97/3) was produced in 93% yield with an enantiomeric excess of 94% (Scheme 47). Moreover, the recycling of the [Bmim]SbF 6 containing the catalyst was possible.…”

Recyclable Stereoselective Catalysts

“…Furthermore, the authors show that the catalytic system and IL could be recycled 16 times with residual enantioselectivity erosion (88% − 92% yields, 10 minutes) [93] . SCHEME 1.14.…”