Alexander N. Tavtorkin

Controlled ring-opening polymerisation of cyclic phosphates, phosphonates and phosphoramidates catalysed by heteroleptic BHT-alkoxy magnesium complexes

We report here that the heteroleptic BHT-Mg(OR) complex, i.e. [(BHT)Mg(OBn)(THF)]2 (Mg3), represents an effective and versatile ring-opening polymerisation (ROP) catalyst for several cyclic ethylene phosphate monomers (CEPMs), such as ethylene phosphates with methoxy- (MeOEP, 1), isopropoxy- (iPrOEP, 2), and tert-butoxy- (tBuOEP, 3) substituents, N,N-diethyl ethylene phosphoramidate (Me2NEP, 4) as well as ethyl (EtPPn, 5) and tert-butyl (tBuPPn, 6) ethylene phosphonates. Mg3 retains its catalytic activity over a broad temperature range from −50 to 100 °C and efficiently carries out the fast and controlled polymerisation of CEPMs with sterically unhindered alkoxy groups with less than 1% chain branching even at near-complete conversion. Compared with ROP catalysed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), Mg3 performs much better in the polymerisation of CEPMs with bulky groups and of monomers sensitive to strong nucleophiles, such as tBuOEP.

Crystal structure and catalytic activity of tetra­kis­(μ2-ethyl 2,6-di-tert-butyl-4-methyl­phenyl phos­phato-κ2O:O′)bis­(ethyl 2,6-di-tert-butyl-4-methyl­phenyl phosphato-κ2O,O′)dilutetium n-heptane disolvate

The title complex {Lu2[(2,6-tBu2-4-MeC6H2-O)(EtO)PO2]6}·2(n-heptane) contains the binuclear [Lu2(μ-OPO)4] core and the phosphate ligands display κ2 O,O′ terminal and μ2-κ1 O:κ1 O′ bridging coordination modes. It demonstrates good catalytic activity in acrylonitrile polymerization.

Synthesis of hydroxydiamines and triamines via reductive cleavage of N–N bond in substituted pyrazolidines

Aliphatic polyamines, being a versatile class of organic compounds, are widely used in many fields of medicine and organic chemistry. However, the general approach to the synthesis of chiral aliphatic polyamines has been still undeveloped. Here, we describe a new method for the synthesis of chiral trifunctional amino compounds, namely hydroxydiamines and triamines. The initial compounds, namely substituted hydroxy- or aminopyrazolidines and pyrazolines, are readily available using convenient stereoselective methods developed earlier by us. The proposed method allows synthesizing of chiral diaminoalcohols and triamines, which are the analogs of a well-known anti-TB drug, namely ethambutol, and cannot be obtained alternatively. The key step of the synthesis is N–N bond cleavage in substituted hydroxy- or aminopyrazolidines and pyrazolines with borane-tetrahydrofuran complex; other known methods for N–N bond cleavage turned out to be ineffective. The main advantage of the proposed method is the retention of a certain configuration of stereocenters in the course of the reaction. Six new chiral diasteomerically pure substituted hydroxydiamines and triamines and the enantiomerically pure triamine with four chiral centers were synthesized and characterized using NMR, IR and mass spectroscopy, as well as elemental analysis.

Titanium–magnesium nanocatalysts of polymerization (Review)

This review addresses the history of the development, structure, properties, and application prospects for a new class of ultrafine catalysts of coordination polymerization, viz., titanium–magnesium nanocatalysts.