The NbCl5–EtMgBr-catalyzed reaction of N,N-disubstituted 2-alkynylamines with Et2Zn followed by hydrolysis or deuterolysis affords (2Z)-alkenylamines (reduction products of alkyne) in high yields.
The reduction of N,N-disubstituted 2-alkynylamines and substituted 3-alkynylols using the NbCl5–Mg reagent system affords the corresponding dideuterated (2Z)-alkenylamine and (3Z)-alkenylol derivatives in high yields in a regio- and stereoselective manner through the deuterolysis (or hydrolysis). The reaction of substituted propargylamines and homopropargylic alcohols with the in situ generated low-valent niobium complex (based on the reaction of NbCl5 with magnesium metal) is an efficient tool for the synthesis of allylamines and homoallylic alcohols bearing a 1,2-disubstituted double bond. It was found that the well-known approach for the reduction of alkynes based on the use of the TaCl5-Mg reagent system does not work for 2-alkynylamines and 3-alkynylols. Thus, this article reveals a difference in the behavior of two reagent systems—NbCl5-Mg and TaCl5-Mg, in relation to oxygen- and nitrogen-containing alkynes. A regio- and stereoselective method was developed for the synthesis of nitrogen-containing E-β-chlorovinyl sulfides based on the reaction of 2-alkynylamines with three equivalents of methanesulfonyl chloride in the presence of stoichiometric amounts of niobium(V) chloride and magnesium metal in toluene.
The reaction of alkyl-and aryl-substituted carboxylic acids with primary and secondary amines under the action of 0.2 equiv. TaCl 5 leads to selective formation of carboxylic acid amides of various structures. TaCl 5 -catalyzed formation of amides was demonstrated to proceed equally selectively both in toluene and methylene chloride, hexane, diethyl ether and 1,4-dioxane solutions.
The Ti(O-iPr)4 and EtMgBr-catalyzed regio and stereoselective carbocyclization of N-allyl-substituted 2-alkynylamines with Et2Zn, followed by deuterolysis or hydrolysis, affords the corresponding methylenepyrrolidine derivatives in high yields.
The reaction between zirconocene dichloride and excess diethylzinc in d-6-benzene solution was studied. It was found that the exchange reaction between Cp2ZrCl2 and Et2Zn is accompanied by the formation of such complexes as bis-(cyclopentadienyl)ethylzirconium chloride (EtZrCp2Cl), a zirconium-organozinc complex, and bis-(cyclopentadienyl)diethylzirconium (Et2ZrCp2). It was also found that as a result of ligand exchange in zirconocene dichloride–diethylzinc bimetallic systems, the zirconium-organozinc complex is formed in minor amounts. An assessment of the thermodynamic stability of the obtained products is given based on the results of DFT analysis. The description of the NMR spectral data of the obtained organozirconium complexes is carried out.
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