Showing papers by "Louis J. Farrugia published in 2002"

2,8′-Disubstituted-1,1′-Binaphthyls: A New Pattern in Chiral Ligands

Abstract: The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15→18), followed by functional group transformations, involving C-P and C-N bond formation (18→19 and 18→23). Racemic intermediate 22 was resolved by cocrystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product).

Semi‐Rigid Bis‐Phosphane Ligands for Metallamacrocycle Formation

Abstract: Efficient syntheses are described for the new bridging bis-phosphanes DPPN (4) and DPEN (5) built around the restricted rigidity of a 2,7-dialkoxynaphthalene backbone. These show marked preference for bridging pairs of metal atoms (PtII, Mo0) to form metallamacrocycles or oligomers. Single-crystal X-ray structure determinations of four dimeric complexes with PtII and Mo0 are reported. The dimeric platinum complexes can be obtained as the kinetically favoured trans,trans products, which isomerise to the cis,cis forms in the presence of free ligand. cis,cis-[Pt2Cl4(DPEN)2] (12) shows marked hydroformylation catalytic activity.

Bioactive flavanones from Luma chequen

Abstract: A bioassay-guided chemical study of a methanolic extract of fresh leaves of Luma chequen led to the isolation of lumaflavanones A (1), B (2) and C (3) whose structures are proposed on the basis of NMR spectroscopic data. The structure of lumaflavanone A was confirmed by X-ray analysis. Antifeedant (Spodoptera littoralis), brine shrimp (Artemia salina) and fungistatic (Botrytis cinerea) bioassays showed that while 3 was the most active in the first two assays the mixture of 1 and 2 was more effective as a fungistatic.

Synthesis and X-Ray Crystal Structures of Fe2Ru(CO)12−n(CNBut)n and FeRu2(CO)12−n(CNBut)n (n=1, 2)

Abstract: The clusters Fe2Ru(CO)12−n(CNBut)n (3, n=1; 4, n=2), FeRu2(CO)12−n(CNBut)n (5, n=1, 6, n=2) and FeRu2(CO)11(CNCy) (5a) have been prepared by direct substitution from the parent carbonyl precursors Fe2Ru(CO)12 (1) and FeRu2(CO)12 (2). All compounds have been characterized spectroscopically and clusters 3, 4, 5, and 6 by single crystal X-ray determinations. In all cases, the isonitrile ligands adopt axial or pseudo-axial positions on a ruthenium atom. The structures of 3–5 are very similar to their parent clusters, but the extent of metal framework disorder is significantly less. Cluster 6 adopts the same C2v Fe3(CO)12 type structure as 4, and thus differs markedly from the parent compound 2, which has a D3 structure .

Bioactive Flavanones from Luma chequen.

Abstract: A bioassay-guided chemical study of a methanolic extract of fresh leaves of Luma chequen led to the isolation of lumaflavanones A (1), B (2) and C (3) whose structures are proposed on the basis of NMR spectroscopic data. The structure of lumaflavanone A was confirmed by X-ray analysis. Antifeedant (Spodoptera littoralis), brine shrimp (Artemia salina) and fungistatic (Botrytis cinerea) bioassays showed that while 3 was the most active in the first two assays the mixture of 1 and 2 was more effective as a fungistatic.