Ilfir R. Ramazanov

‘One-pot’ synthesis of 1,1-disubstituted cyclopropanes in the presence of metal complex catalysts

Abstract A ‘one-pot’ catalytic method for the synthesis of 1,1-disubstituted cyclopropanes starting from olefins, acetylenes and AlEt 3 in the presence of Cp 2 ZrCl 2 , via a step involving in situ formation of aluminacyclopentanes and aluminacyclopentenes, respectively, was developed. Five-membered organoaluminium compounds obtained without preliminary isolation are transformed to cyclopropanes under the effect of Ni(acac) 2 in combination with allylhalogenides in the case of aluminacyclopentanes and alkylsulphates in experiments with aluminacyclopentenes.

Acetylene cyclopropanation by CH2I2–Et3Al reagent

Abstract The one-step method for a synthesis of 1,1,2-trialkyl- and 1,1,2,2-tetraalkylsubstituted cyclopropanes from mono- and dialkylsubstituted acetylenes, CH 2 I 2 and Et 3 Al was developed.

Cobalt-Catalyzed [6 + 2] Cycloaddition of Alkynes with 1,3,5,7-Cyclooctatetraene as a Key Element in the Direct Construction of Substituted Bicyclo[4.3.1]decanes

A new, effective catalytic system based on Co(acac)2 has been developed for [6 + 2] cycloaddition of terminal alkynes to 1,3,5,7-cyclooctatetraene to give substituted bicyclo[4.2.2]deca-2,4,7,9-tetraenes in high yields (68-85%). The electrophilic activation of double bonds in the bicyclic products with m-CPBA is an efficient method for the synthesis of substituted bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols, which form the key structural moieties of numerous natural biologically active compounds. The structures of the obtained compounds were reliably proven by modern spectral methods and X-ray diffraction. The mechanism of the discovered rearrangement was studied both using deuterium-labeled bicyclo[4.2.2]deca-2,4,7,9-tetraenes and utilizing quantum chemical calculations. The obtained substituted bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols and their keto derivatives showed high antitumor activity in vitro against Hek293, Jurkat, K562, and A549 tumor cell lines.

Synthesis and transformations of metallacycles: 21. A novel method for the synthesis of 1,1-dialkylcyclopropanes

A regioselective method for the synthesis of 1,1-dialkylcyclopropanes was developed. The method is based on the reaction of 2,3-dialkyl-1-ethylalumacyclopent-2-enes with an excess of dialkyl sulfates (Me2SO4 or Et2SO4). A plausible reaction mechanism was suggested.

One-step cyclopropanation of alkynes with diiodomethane and triethylaluminum

Cyclopropanation of mono- and dialkyl-substituted alkynes under the action of CH2I2 and Et3Al afforded the corresponding 1-alkyl- and 1,2-dialkyl-substituted 1,2-diethylcyclopropanes in 65—80% yields.

Synthesis and transformations of metallacycles. 24. Zr-Catalyzed cycloalumination of asymmetrical disubstituted acetylenes

Cp2ZrCl2-Catalyzed cycloalumination of asymmetrical alkyl-, phenyl-, and allyl-substituted acetylenes under the action of Et3Al was studied. The reactions afforded regioisomeric 2,3-disubstituted aluminacyclopent-2-enes whose yields and ratio depend on the nature of the substituents in the starting acetylenes.

13C NMR SPECTRA AND ELECTRONIC STRUCTURE OF ALKENYLALANES

The parameters of13C NMR spectra of linear and cyclic alkenylalanes synthesized from mono- and disubstituted acetylene and the simplest alkylalanes have been obtained. A strong paramagnetic effect of the aluminum atom on shielding of α- and β-carbon atoms at the double bond has been observed for the dimeric form of organoaluminum compounds (OAC) in inert solvents, unlike that for the monomeric form solvated in electron-donor solvents (Et2O, THF, and Et3N). The results were interpreted in terms of the model of the electron density redistribution on going from the dimeric structure of OAC to the monomeric one. The PM3 method describes most adequately (as compared to MNDO and AM1) the equilibrium geometry of cyclic dimers of OAC.

Bu2iAlCl-Cp2TiCl2 — A new reagent for hydroalumination of disubstituted acetylenes

A new regio- and stereoselective method for the synthesis ofE-alkenylchloralanes based on Cp2TiCl2-catalyzed hydroalumination of disubstituted acetylenes by diisobutylaluminum chloride was developed. Hydrolysis and deuterolysis of organoaluminum compounds lead to the correspondingZ-olefins, and cross-coupling with ally) halides in the presence of Pd(Ph3P)4 results in the formation ofcis-4,5-disubstituted 1,4-dienes.

New method for cycloalumination of disubstituted acetylenes with 1,2-dichloroethane

A new procedure has been developed for the synthesis of 2,3-dialkyl(phenyl)aluminacyclopent-2-enes by Cp2TiCl2-catalyzed cycloalumination of disubstituted acetylenes with EtAlCl2 in the presence of ethylene generated in situ from 1,2-dichloroethane and activated magnesium.

Aluminum carbenoids in the cyclopropanation of fulvenes

Aluminum carbenoid Et2AlCH2I reacts with 6-substituted fulvenes to give tricyclopropanes in high yields. Calculations at the B3LYP/6-31G(d) level of theory show that coplanar arrangement of the double bonds facilitates cyclopropanation due to conjugation in the transition state. Aluminum carbenoid Et2AlCH2I was generated by either the reaction of equimolar amounts of Et3Al and CH2I2 in hexane or treatment of Et2AlI with CH2N2 in dichloromethane.