Cage Chirality of PC Cage Compounds: Highly Diastereoselective Formation of Diastereomeric P₅‐Deltacyclenes, Separation of Diastereomers, and Removal of the Chiral Auxiliary

Abstract

An effective cyclic addition reaction of diastereomeric (R*)diphenyltin-3,5-di(tert-butyl)-1,2,4-triphosphole derivatives 6 a-c (R* = (-)-cis-myrtanyl (a), (-)-trans-myrtanyl (b), m-(2-bornyl-2-ene)phenyl (c) with two equivalents of tert-butylphosphaalkyne 1 leads to 1:1 mixtures of diastereomeric stannylated pentaphosphadeltacyclene derivatives 7 a-c with seven stereogenic centers in the cage unit. The (-)-cis-myrtanyl derivative 7 a could be separated into its diastereomers; destannylation of diastereomer 7 a(RR) led to the P-H cage 8 as a pure enantiomer. Circular dichroism (CD) spectroscopy of the pure diastereomer 7 a(RR) and the enantiomer 8 give evidence for identical stereoisomers of the P(5)-deltacyclene cage units and prove a strong dominance of the chiral cages over the chiral auxiliary groups with respect to their chiroptical properties. Absolute X-ray structure investigations of the majority of the compounds presented in the paper reveal the details of the stereochemistry of the asymmetric P-C cage units. In this paper we demonstrated for the first time a general preparative route to stereochemically fully defined asymmetric P-C cage compounds by separation of diastereomers and replacement of the chiral auxiliary group.

Opening “Jaws”: Functionalisation of the hexaphosphapentaprismane cage, P6C4Bu4, affording X2P6C4Bu4 (X = Me, I), crystal and molecular structures of X2P6C4Bu4 (X = Me, I) and [cis-PtCl2Me2P6C4Bu4]

“…A recent exciting development has been the synthesis of chiral cage compounds of the P 5 -deltacyclene type and removal of the chiral auxiliary [3].…”

Diphospholyl and triphospholyl zirconium π-complexes: Ziegler–Natta oligomerization catalysts and reactive intermediates in P–C cage formation by hydrolysis

“…Intensity data were collected on Bruker-Nonius KappaCCD (4,5,6) or Siemens P4 (8,9,10) diffractometers (u-and x-rotations) using Mo Ka radiation (graphite monochromator, k = 0.71073 pm). Data were corrected for Lorentz and polarization effects.…”

“…Absorption effects have been taken into account on a semiempirical basis using multiple scans of equivalent reflections (SADABS, Bruker-AXS, 2002) [32,33]. All structures were solved by direct methods and refined by full-matrix least-squares procedures against F 2 with all reflections using SHELXTL-NT 5.10 (Bruker AXS, 1998) (4,8,9,10) or SHELXTL-NT 6.12 (Bruker AXS, 2002) (5, 6) programs [34]. All non-hydrogen atoms were refined anisotropically.…”

“…12.026 cage compounds by cyclic addition reactions of the released and partially modified ligands. We are deeply interested in P-C cage chemistry on the basis of unsaturated P-heterocycles, as we detected an inherent and very high diastereoselectivity for chiral species [7], which led us actually to the novel class of optically active cage-chiral P-C cage compounds [8].…”

Stereoselective P5-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds

“…A novel aspect of this field of chemistry are optically active derivatives of chiral P‐C cage compounds . As a specific property of the derivatives of 3 , a once established enantiomeric excess remains untouched by all reactions tested to date which do not disintegrate the molecules such as destannylation, protonation, deprotonation, complexation,, oxidation, and cage rearrangement including cage inversion . In spite of its five P‐lone pairs and a dynamic equilibrium between two epimers, P‐H P 5 ‐deltacyclene 5 (Scheme ) proved to be a highly selective ligand with metals of interest for catalytic applications.…”