Aleksandr N. Kostyuk

N-Phosphorylated Imidazolium Salts as Precursors to 2- and 5-Phosphorylated Imidazoles and New Imidazol-2-ylidenes Featuring the PNCN Unit

It has been experimentally proven that the reaction of 1- or 1,2-disubstituted imidazoles with diorganylphosphorus(III) halides proceeds via initial formation of N-phosporylated imidazolium salts. Treatment of these salts with strong bases results in phosphorylation of the parent imidazoles at the 2- or 5-positions, correspondingly. In a previous case, imidazol-2-ylidenes are formed as intermediates. With both N1 and N3 atoms bearing sterically demanding or/and π-donating groups, deprotonation of 1,3-disubstituted imidazolium salts with NaN(SiMe(3))(2) afforded new stable N-phosphorus-substituted Arduengo-type carbenes.

Electrophilic substitution as a convenient approach to functionalized N-benzyl-1,4-dihydropyridines

The reactivity of 1-benzyl-3-cyano-1,4-dihydropyridine was studied in reactions with electrophilic reagents based on structural analogy of 1,4-dihydropyridines with enamines. Different 5-functionalized derivatives were obtained by direct electrophilic substitution.

Direct Phosphorylation of N-Protected Imidazoles and Benzoimidazoles-A Route to 1H-Imidazol(benzoimidazol)-2-yl Phosphonic and Phosphinic Acids and Their Derivatives

Abstract Synthetic approaches to 1H-imidazol-2-yl and 1H-benzoimidazol-2-yl phosphinic and phosphonic acids and their derivatives are reported, based on phosphorylation of N-protected heterocylcles by PhPOCl2 or MePOCl2. Reaction of N-alkylbenzoimidazoles with POCl3 did not lead to C-phosphorylated products in a reasonable yield, [2,2′]-bis-benzoimidazolyles being formed instead.

PHOSPHORYLATION OF 5-ARYLMETYLIDENE-1-MORPHOLINOCYCLOPENTENES

Abstract The phosphorylation reaction of 5–arylmethylidene–1–morpholinocyclopentenes with various phosphorus (III) and (V) halides was studied. It was shown that the enamines react with phosphorus (III) halides giving stable halo– and dihalophosphines which are key substances for further synthesis. Hydrolysis of the phosphorylated enamines does not afford the expected phosphorylated ketones, decomposition being observed in acidic media.

Synthesis and characterization of 4,5-dihydro-1H-pyrazolo[3,4b][1,4]azaphosphinines

1,3,3-Trimethyl-2-(1-R-3-methyl-5-pyrazolyliminoethylidene)indolines were shown to undergo phosphorylation with phosphorus(III) halides at the two nucleophilic carbon centers to give fused 1,4-azaphosphinine ring systems. Chemical properties of the synthesized compounds were characterized. For some representative compounds, detailed NMR spectroscopic investigations were performed, including the determination of 31P, 1H and 31P, 13C coupling constants.

PHOSPHORYLATION OF ENAMINEHYDRAZONES AS AN EFFICIENT ROUTE TO DIAZAPHOSPHOLINES AND DIAZAPHOSPHOLES

Abstract 1,2,3-diazaphospholines of new type containing an enamine residue, conjugated with the diazaphospholine cycle, were synthesized by phosphorylation of N,N-dimethyl- and N-substituted hydrazones of ω-fomyl-1,3,3-trimethyl-2-methyleneindolines using phosphorus(III) halides. Reversible ionization of the P-Br bond was observed for a 2-N-methyl-3-P-bromodiazaphospholine in polar solvents. The ionization is caused by stabilization of the phosphenium ion by electrondonating methyl and enamine group. Analogously, 2-N-phenyl-3-P-bromo- as well as 3-P-chloro-1,2,3-diazaphospholines give stable phosphenium ions only after treatment of sodium tetraphenylborate or trimethylsilyl trifluoromethanesulfonate.

Electrocyclization of phosphahexatrienes: an approach to λ5-phosphinines.

We experimentally verified an assumption that the substitution of a carbon atom with a pentavalent phosphorus atom in 1-alkoxy (dialkylamino) hexatrienes will not hamper its ability to electrocyclize. A series of 1-, 3-, and 5-phosphahexatrienes were synthesized. It was shown that parent λ(5)-phosphinines could be synthesized by electrocyclization of the 3- and 5-phosphahexatrienes. The resultant electrocyclization is a convenient method for the synthesis of parent λ(5)-phosphinines bearing different substituents on the phosphorus atom.

Phosphorus‐Containing Heterocyclic Compounds Derived from N‐Vinylpyrroles

C-phosphorylation of N-vinylpyrroles with phosphorus(III) halides is shown to occur both at position 2 of the pyrrole ring and at the vinyl group. The properties of the resulting phosphorus-containing heterocyclic compounds and bis-phosphorylated N-vinylpyrroles are reported.

1,2‐migration in N‐phosphano functionalized N‐heterocyclic carbenes

1,2‐Migration of the phosphano‐group to the carbene center in N‐phosphano functionalized N‐heterocyclic carbenes has been studied by density functional theory (DFT) calculations. An intramolecular mechanism with a three‐center transition state structure seems to be most plausible for the isolated carbenes, while an intermolecular pathway catalyzed by azolium salts may be preferable for a migration proceeding in the course of generating the carbenes in situ. Our calculations show that amino‐substitution at the phosphorus atom and an enhanced nucleophilicity of the heterocycle scaffold facilitate the phosphorus shift. Calculated singlet‐triplet energy gaps do not correlate with thermodynamic stability of the studied carbenes and their disposition toward the 1,2‐rearrangement.

Stable N-Phosphorylated Triazol-5-Ylidenes

Abstract Novel N-phosphorylated triazolium salts have been synthesized. They react with sodium bis(trimethylsilyl)amide to produce new stable N-phosphorylated triazole-5-ylidenes, which rearrange to C-phosphorylated triazoles under heating. The formation of two silver carbene complexes is described. Representative carbene and carbene complex structures were determined by X-ray study. GRAPHICAL ABSTRACT