Zusammenfassung
The (+)-9-phenyldeltdcyclanyl moiety as a chiral phosphorus substituent contains eight configurationally fixed asymmetric carbon atoms, It is easily obtained from the reaction of norbornadiene and phenylacetylene via a Co-catalyzed enantioselective homo-Diels-Alder reaction, to give (+)-8-phenyldeltdcyclene. In the reaction of (+)-8-phenyldeltacyclene with 1,2-(H2P)(2)C6H4 the trisubstitution ...
Zusammenfassung
The (+)-9-phenyldeltdcyclanyl moiety as a chiral phosphorus substituent contains eight configurationally fixed asymmetric carbon atoms, It is easily obtained from the reaction of norbornadiene and phenylacetylene via a Co-catalyzed enantioselective homo-Diels-Alder reaction, to give (+)-8-phenyldeltdcyclene. In the reaction of (+)-8-phenyldeltacyclene with 1,2-(H2P)(2)C6H4 the trisubstitution product PPP'-tris[(+)9-phenyldeltacyclan-8-yl)-1,2-bis(phosphanyl) benzene, (+)(delta)-LH, is obtained, in which a single P-H bond at the stereogenic phosphorus atom is left. (+)(delta)-LH crystallizes as a pure diastereomer, which isomerizes in solution with respect to the secondary phosphorus atom at -20 degreesC resulting in a 64:36 diastereomer mixture. Substitution of the P-H hydrogen atom in (+)(delta)-LH by benzyl, 3-bromobenzyl, 6-bromo-n-hexyl and 3-(diphenylphosphanyl)phenyl gave the bis(tertiary) diphosphanes (+)(delta)-LR1-(+)(delta)-LR4. NiBr2, PdIIal(2) (Hal = Cl, Br, I) and PtHal(2) (Hal = Cl, Br) complexes of (+)(delta)-LH and (+)(delta)-LR1-(+)(delta)-LR4 have been synthesized. The complexes form two diastereomers differing in the configuration of the chiral P atom. X-ray structure analyses have been carried out -with (+)(delta)-LH, [(+)(delta)-LR2]NfBr(2), [(+)(delta)-LH]PdI2 and [(+)(delta)-LCI]PdI2. Interestingly, for [(+)(delta)-LH]PdI2 both diastercomers are found in the same crystal lattice in a 1: 1 ratio. In [(+)(delta)LH]PdI2 and [(+)(delta)-LCl]PdI2 the configuration at the secondary phosphorus atom is stable in solution at room temperature, whereas in the free ligand (+)(delta)-LH it is configurationally labile, ((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
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