SCHEDULED MAINTENANCE
Diamidophosphites from β-hydroxyamides: readily assembled ligands for Pd-catalyzed asymmetric allylic substitution†
*a
Konstantin N.
Gavrilov,
a
Nataliya E.
Borisova,
b
Sergey V.
Zheglov,
a
Vladislav K.
Gavrilov,
a
Ilya D.
Firsin,
a
Igor S.
Mikhel,
d
Vladimir V.
Chernyshev
bd
and
Nataliya S.
Goulioukina
abd
Abstract
Two groups of modular chiral diamidophosphite ligands were easily synthesised from accessible N-Boc-amino alcohols and pseudodipeptides. The reaction of these compounds with [Pd(allyl)Cl]2 in the presence of AgBF4 yielded complexes [Pd(allyl)(L)2]BF4. In addition, metallochelates [Pd(allyl)(L)]BF4 with (S)-methioninol-based P,S-bidentate ligands were prepared. The structures of the novel ligands and complexes were elucidated by means of 2D-NMR and were confirmed by single-crystal X-ray diffraction, as well as by DFT calculations. Asymmetric inducers of this type exhibited high enantioselectivities in the Pd-mediated allylic substitution of (E)-1,3-diphenylallyl ethyl carbonate with CH2(CO2Me)2 (up to 98% ee) and (CH2)4NH (up to 92% ee). Ee values of up to 86% and 73% were obtained in the Pd-catalyzed allylic alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate and ethyl 2-oxocyclopentane-1-carboxylate, respectively. The effects of the structural modules, such as the nature of the phosphorus-containing ring or exocyclic substituent, on the catalytic activity and enantioselectivity were investigated.
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