Levon L. Khemchyan

The comparison of addition of molecules possessing P(V)-H bond to alkynes catalyzed with Pd and Ni complexes

Main factors have been analyzed necessary for creation of an efficient catalytic system for alkynes hydrophosphorylation based on nickel complexes, and a valid model system was suggested for the comparison with palladium complexes. It has been discovered for the first time that the insertion of an alkyne into the metal-hydrogen bond occurs with a considerably lower activation barrier than into the metal-phosphorus bond, whereas the variation in the reaction energy corresponds in both cases to an exothermic reaction. Under the optimized conditions the transformation catalyzed by nickel complexes does not require acid addition and may proceed even in the absence of a phosphine ligand.

Exclusive selectivity in the one-pot formation of C-C and C-Se bonds involving Ni-catalyzed alkyne hydroselenation: optimization of the synthetic procedure and a mechanistic study.

A unique Ni-catalyzed transformation is reported for the one-pot highly selective synthesis of previously unknown monoseleno-substituted 1,3-dienes starting from easily available terminal alkynes and benzeneselenol. The combination of a readily available catalyst precursor, Ni(acac)2, and an appropriately tuned phosphine ligand, PPh2Cy, resulted in the exclusive assembly of the s-gauche diene skeleton via the selective formation of C-C and C-Se bonds. The unusual diene products were stable under regular experimental conditions, and the products maintained the s-gauche geometry both in the solid state and in solution, as confirmed by X-ray analysis and NMR spectroscopy. Thorough mechanistic studies using ESI-MS revealed the key Ni-containing species involved in the reaction.

Synthesis of Phosphorus Compounds via Metal-Catalyzed Addition of P–H Bond to Unsaturated Organic Molecules

In the present chapter we discuss transition-metal-catalyzed phosphorus-hydrogen (P–H) bond addition to the triple bond of alkynes and to the double bond of alkenes, dienes, imines, aldehydes and ketones. Main attention is paid to highlight the factors responsible for development of highly efficient catalytic systems and to carry out the addition reaction with high stereo-, regio- and enantioselectivity.

Synthesis of alkyl tetraphosphonates: First example of nickel catalyst for H-phosphonates addition to diynes

Efficient algorithm was developed for the analysis of products of the catalytic reaction of diynes multiphosphorylation based on combined application of 31P NMR DOSY spectra and HPLC-MS method. Using this analytical approach the reaction of H-phosphonates addition to diynes was investigated and a simple synthetic procedure got alkyl tetraphosphonates preparation was developed.

Efficient Sustainable Tool for Monitoring Chemical Reactions and Structure Determination in Ionic Liquids by ESI-MS.

An easy and convenient procedure is described for monitoring chemical reactions and characterization of compounds dissolved in ionic liquids using the well-known tandem mass spectrometry (MS/MS) technique. Generation of wastes was avoided by utilizing an easy procedure for analysis of ionic liquid systems without preliminary isolation and purification. The described procedure also decreased the risk of plausible contamination and damage of the ESI-MS hardware and increased sensitivity and accuracy of the measurements. ESI-MS detection in MS/MS mode was shown to be efficient in ionic liquids systems for structural and mechanistic studies, which are rather difficult otherwise. The developed ESI-MS/MS approach was applied to study samples corresponding to peptide systems in ionic liquids and to platform chemical directed biomass conversion in ionic liquids.