Research summary

Our research is focused on metalation reactions directed by phosphorus-containing functional groups as a tool for developing new methodology with applications in asymmetric synthesis, coordination chemistry, and catalysis. The rational design of the synthetic work is supported by mechanistic studies of the transformations through multinuclear magnetic resonance. Recently, we have extended the use of NMR techniques, especially HRMAS, in combination with statistical methods to metabolic studies of vegetables produced under greenhouses.
Please consult our publications page for more detailed information about each of these topics.

Main specific research interests:

• Ortho and Calpha directed metalation of organophosphorus reagents (phosphazenes, phosphinic and phosphonic acid derivatives). Applications in organic synthesis (olefins, heterocycles, peptidomimetics).

Selective Calpha, Cortho, and NCalpha lithiation of organophosphorus compounds containing the Ph2P=X moiety followed by electrophilic quench affords new functionalized derivatives that can be transformed into a variety of highly added value molecules.

• Synthesis of complexes of copper, gold, yttrium and lanthanides. Applications in catalysis.

The reaction of the Calpha,Cortho dilithiated phosphazene 1 with CuBr provided the first example of a binuclear mixed valence [CuI(N2)/CuIII(C4)] complex 2 showing a metal-metal bond. This complex catalyzed prototypal oxidation and cyclopropanation reactions involving Cu(I) and/or Cu(III) species.

The first cycloaurated gold(III) phosphinamide complex 5 in which a phosphinamide moiety acts as a new C-C-P-O pincer ligand has been prepared through Sn(IV)-Au(III) transmetallation reactions of 3 and 4. Complex 5 is an excellent catalyst for the synthesis of propargylamines via three-component condensation of aldehydes, alkynes, and amines.

A new meso-bisphosphinic amide/phosphine oxide tridentate ligand (RP*,SP*)-6 has been synthesized through ortho-lithiation of N,N-diisopropyl-P,P-diphenylphosphinic amide followed by reaction with phenylphosphonic dichloride. Mixing 6 with Y(NO3)3·6H2O in a ligand to metal molar ratio of 1:1 and 2:1 afforded complexes 7 and 8, respectively.

• Investigation of reaction mechanisms involving organometallic species through NMR. (e.g. 6/7Li, 29Si, 57Fe, 73Ge, 89Y, 103Rh, 113Cd, 119Sn, 199Hg, etc.).

The first step of our synthetic work consist of a lithiation directed by a Ph2P=X group. NMR monitoring the lithiation step in combination with DFT computational studies allows for a rational design of the synthesis. We have developed a NMR methodology based on 31P detection to get structural information through correlations with non conventional nuclei. Of particular interest for us are 7Li and 89Y. Representative examples of the species identified in solution are shown below.

NCalpha lithiated phosphinamides: Chem. Commun., 1142 (2004)		Cortho Lithiated phosphinamides J. Am. Chem. Soc., 132, 5193 (2010)
Calpha/Cortho Lithiated phosphazenes Chem. Commun., 4674 (2007)	Speciation of Y3+/Ph3PO complexes Dalton Trans., 40, 2425 (2011)

• Metabolic profiling of vegetables through NMR.

HRMAS NMR in combination with unsupervised multivariate analysis have been used to study metabolite changes associated to tomato ripening and tissue differentiation. Flesh, peel and seeds from mature red fruits were separately analyzed.

Left: 1H HRMAS NMR spectrum of a sample of RAF tomato including labelling of selected metabolites. Right: PCA analysis (score plot) of RAF tomato in three mature stages, Food Chem., 122, 877 (2010).