Chiral Phosphinoferrocenyl‐Calixarenes
The Mitsunobu alkylation of 4-tert-butylcalix[4]arene with (S)-(2-diphenylthiophosphinoferrocenyl)methanol followed by desulfuration of the thiophosphine unit using tris(dimethylamino)phosphine afforded enantiomerically pure calixarene mono- and di(ferrocenylphosphine) ligands in high yields. The calixarene mono(ferrocenylphosphine) ligands exhibited good catalytic activity but low atropoenantioselectivity when used in the asymmetric Suzuki–Miyaura coupling reaction of 1-naphthaleneboronic acid and 1-bromo-2-methylnaphthalene. However, the di(ferrocenylphosphine) ligand displayed both good catalytic activity and enantioselectivity (ee values up to 86 %) when employed in the asymmetric Tsuji–Trost allylic alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate.