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A study of the secondary interactions involving a pendant phenethyl group (NCH(CH 3 )Ph) of (S a ,R C ,R C )-O,O′-[1,1′-binaphthyl-2,2′-diyl]-N,N′-bis[1-phenylethyl]phosphoramidite (1) in d 8 and d 6 metal complexes is reported. A 1,2-η-phenyl interaction is found in [Pd(η 3 -allyl)(1,2-η-Ph-1-κP)] + (3), as indicated by NMR spectroscopy and by an X-ray study. The Rh(I) complexes [RhCl(NBD)(1-κP)] (4a) and [RhCl(COD)(1-κP)] (4b) were prepared, and their X-ray structures were determined. Chloride abstraction from 4a and 4b gave the corresponding cations [Rh(NBD)(1,2-η-Ph-1-κP)] + (5a) and [Rh(COD)(1,2η-Ph-1-κP)] + (5b), which were fully characterized. Besides NMR spectroscopic data, the 1,2-η-phenyl interaction is supported by an X-ray study of 5a. Upon standing in MeOH solution, 5b undergoes loss of the COD and forms [Rh(1-κP)(η 6 -Ph-1-κP)] + (6), whose η 6 -arene coordination was studied by NMR spectroscopy and by X-ray diffraction. For the sake of comparison with the d 8 complex 6, the crystal structure of the previously reported d 6 analogue [RuCl 2 (η 6 -Ph-1-κP)] + (7) was determined. This study shows that secondary π-arene-metal interactions turn phosphoramidite 1 to a four-, six-, or eight-electron donor, with increasing bond strength in this order.

Chiral phosphines are pre-eminent ligands in asymmetric catalysis and are utilized in applications ranging from laboratory syntheses to industrial processes.[1] Despite their wide-spread use in enantioselective catalysis, there are surprisingly few syntheses of chiral phosphines by enantioselective methods. Thus, it is of interest to develop such reactions because catalytic asymmetric transformations in which the P À C bond and stereogenic centers are simultaneously formed might allow access to new chiral motifs, give more efficient syntheses of valuable chiral ligands, and stimulate the development of new enantioselective processes.Recently, a few strategies for catalytic PÀC bond formations have emerged that give enantiomerically enriched phosphines.[2] It is noteworthy that these systems frequently find close parallels in N À C bond formations. For example, organolanthanide compounds catalyze both intramolecular hydroaminations and hydrophosphinations, apparently through analogous mechanisms.[3] Also, our group has described a nickel(II) catalyst which is active for asymmetric hydroamination and hydrophosphination of vinyl nitriles. [4] Finally, of particular relevance are palladium-catalyzed aryl-X/E-H (E = N, P) coupling reactions, which have shown tremendous synthetic utility.[5] Thus, new catalytic asymmetric phosphine synthesis might be guided by examples from the corresponding amine chemistry. In this context, it is of interest to note that although asymmetric allylic amination is a prominent method for the preparation of chiral amines, [6] there are no reports of asymmetric allylic phosphination (Scheme 1). Additionally, a pendant allylic group would offer the possibility of further functionalizations, and allylic alkylations and aminations have been shown to be useful in synthesis. [7] There are, however, several examples of non-enantioselective catalytic syntheses of allylic phosphonates, which all involve Pd 0 -or Ni 0 -catalyzed coupling of phosphonates and allylic substrates.[8] Furthermore, Moreno Maaeas and coworkers have synthesized allylic phosphonium salts by the reaction of allylic pyridinium salts and triphenylphosphine in the presence of [Pd(PPh 3 ) 4 ].[9] Most notably, this complex was shown 25 years ago by Fiaud to catalyze the reaction of lithium diphenylphosphide with aliphatic allylic acetate derivatives to afford the corresponding substitution products.[10] However, to our knowledge these transition-metalcatalyzed reactions do not appear to have ever been attempted in the presence of chiral ligands. Finally, the advent of organocatalytic processes in recent years has led to the development of an enantioselective 1,4-addition of secondary phosphines to a,b-unsaturated aldehydes, giving products in up to 98 % ee.[11]Based on previous work in the area of asymmetric allylic substitutions [12] and on our hydroamination/hydrophosphination chemistry, [4] we began to pursue asymmetric allylic phosphination. We initially examined reactions of 1,3-diphenylallyl ethyl carbonate (1 a; Sche...

The gold(I)-or Brønsted acid-catalyzed reaction of unactivated vinylcyclopropanes (VCPs) with sulfonamides affords useful homoallylic amine derivatives. This ring-opening reaction occurs in a highly selective manner affording in the case of aphenyl-substituted VCPs products with the E-configuration exclusively.Keywords: catalysis; gold; hydroamination; ringopening; vinylcyclopropanes Unactivated vinylcyclopropanes (VCPs) are potentially best-suited substrates for transition metal-catalyzed reactions involving ring-opening processes. However, only a limited number of such transformations has been reported so far. These include the classical rearrangement to cyclopentenes and related reactions, [1a-c] [5 + 2] cycloadditions, [1d,e] couplings with aldehydes,

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