Synthesis of 1-Phosphabarrelene Phosphine Sulfide Substituted Palladium(II) Complexes

phosphinine - phosphabarrelene - crystallographic study - S,P-ligands

Significance

A general Diels-Alder-based synthesis of 1-phosphabarrelenes from substituted phosphinines is reported. Palladium complexes have been prepared which serve as good ligands for cross-coupling reactions and in the allylation of secondary amines with TON up to 7 × 10⁶. X-ray crystal structural analysis and computational data of the complexes are presented.

Comment

The phosphabarrelenes, P-analogues of the classical barrelene (H. E. Zimmerman, R. M. Paufler J. Am. Chem. Soc. 1960, 82, 1514-1515) represent a unusual class of heterocycles and phosphorus ligands, which have received little attention (B. Breit, E. Fuchs Chem. Commun. 2004, 694-695). Aside from interest in its chemical reactivity, the three-dimensional heterocyclic core opens new horizons for rational ligand design not only for conventional Pd-catalyzed cross-coupling reactions but also for asymmetric catalytic processes.