The TaCl-Mediated Reaction of Dimethyl 2-Phenylcyclopropane-1,1-dicarboxylate with Aromatic Aldehydes as a Route to Substituted Tetrahydronaphthalenes.

It is found that the reaction of dimethyl 2-phenylcyclopropane-1,1-dicarboxylate with 2 equivalents each of aromatic aldehydes and TaCl in 1,2-dichloroethane at 23 °C for 24 h after hydrolysis gives substituted 4-phenyl-3,4-dihydronaphtalene-2,2(1)-dicarboxylates in good yield. This represents a new type of reactions between 2-arylcyclopropane-1,1-dicarboxylates and aromatic aldehydes, yielding chlorinated tetrahydronaphthalenes with a arrangement of the aryl and chlorine substituents in the cyclohexene moiety. A plausible reaction mechanism is proposed.

CpZrCl - EtAl reagent system in the homo-coupling of trimethylsilyl-substituted alkynes.

The reaction of trimethylsilyl-substituted alkynes with 0.5 equivalents of CpZrCl and 1 equivalent of EtAl in toluene at room temperature for 18 hours gives, after hydrolysis/deuterolysis or iodination, functionalized products of the homo-coupling of silyl-substituted alkynes in good yield. Trimethylsilyl-substituted α,ω-diynes react with the CpZrCl - EtAl reagent system to give (1,2)-1,2-bis(iodo(trimethylsilyl)methylene)cycloalkanes after iodinolysis.

NbCl-Mg Reagent System in Regio- and Stereoselective Synthesis of (2)-Alkenylamines and (3)-Alkenylols from Substituted 2-Alkynylamines and 3-Alkynylols.

The reduction of ,-disubstituted 2-alkynylamines and substituted 3-alkynylols using the NbCl-Mg reagent system affords the corresponding dideuterated (2)-alkenylamine and (3)-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 NbCl 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 TaCl-Mg reagent system does not work for 2-alkynylamines and 3-alkynylols.

Niobium- and zirconium-catalyzed reactions of substituted 2 alkynylamines with EtZn.

The NbCl-EtMgBr-catalyzed reaction of ,-disubstituted 2-alkynylamines with EtZn followed by hydrolysis or deuterolysis affords (2)-alkenylamines (reduction products of alkyne) in high yields. The reaction of ,-disubstituted 2-alkynylamines with EtZn catalyzed by the CpZrCl-EtMgBr system occurs as 2-zincoethylzincation, resulting, after deuterolysis or iodinolysis, in the regio- and stereoselective formation of the corresponding dideuterated and diiodinated 2-alkenylamine derivatives with a trisubstituted double bond. This study demonstrates the difference between the catalytic effects of NbCl and CpZrCl on the pathway of reaction of tertiary 2-alkynylamines with EtZn in the presence of catalytic amounts of EtMgBr.

Synthesis of heteroatom-containing pyrrolidine derivatives based on Ti(O-Pr) and EtMgBr-catalyzed carbocyclization of allylpropargyl amines with EtZn.

The Ti(O-Pr) and EtMgBr-catalyzed regio and stereoselective carbocyclization of -allyl-substituted 2-alkynylamines with EtZn, followed by deuterolysis or hydrolysis, affords the corresponding methylenepyrrolidine derivatives in high yields. It was found that Ti-Mg-catalyzed carbocyclization of -allyl-substituted 2-alkynylamines with EtZn is equally selective in dichloromethane, hexane, toluene, and diethyl ether. The reaction was tolerant to the presence of aryl, alkyl, trimethylsilyl, methoxymethyl and aminomethyl substituents on the alkyne.