Regiochemistry of the addition of mercury salts to bornylene

The dependence of the regiochemistry of the mercuration of bornylene on the nature of the mercurating reagent and on the solvent has been found. The structures of the intermediate and transition state in these reactions have been proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 501–505, March, 1994.     

Reactions of mercury salts with benzo- and tetrafluorobenzobarrelenes

Regiochemistry and stereochemistry of the addition of mercury salts to benzobarrelene and tetrafluorobenzobarrelene have been studied in acetic acid and methanol. The effect of the substrate structure on the regiochemistry of the reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1994.     

Synthesis of new acyclonucleosides comprising unexpected regioisomers in the case of purines

Acyclonucleosides 4 have been obtained by a short way starting from ethyl 2-hydroxymethyl acrylate 5. The key intermediate was acetate 9. Its reaction with free or protected nucleic bases gave either the expected compounds or unusual regioisomers.     

PhPMe2 ligand substitution in the tetracobalt cluster Co4(CO)10(μ4-PPh)2: X-ray diffraction structure of Co4(CO)8(PPhMe2)2(μ4-PPh)2

The thermal substitution chemistry of the tetracobalt cluster Co₄(CO)₁₀(₄-PPh)₂ with the phosphine ligand PhPMe₂ (2.5 equiv) has been explored and found to afford the bis(phosphine)-substituted cluster Co₄(CO)₈(PPhMe₂)₂(₄-PPh)₂ as the major reaction product. The regiochemistry and stereoselectivity exhibited by the two phosphine ligands in Co₄(CO)₈(PPhMe₂)₂(₄-PPh)₂ have been unambiguously established by X-diffraction analysis as having a 1,3-cis orientation. Co₄(CO)₈(PPhMe₂)₂(₄-PPh)₂ crystallizes in the monoclinic space group P2₁/n,a=10.314(1) Å,b=18.051(3) Å,c=21.313(2) Å, =90.10(1)°,V=3968.0(8) ų,Z=4,d _calc=1.590 g cm^–3;R=0.051,R _w=0.042 for 4987 observed reflections withI>3(I). Generalizations concerning the stereochemical disposition of two P-ligands about the Co₄(CO)₈P₂(₄-PPh)₂ (where P=phosphine or phosphite) polyhedron are discussed with respect to the cone angle of the P-ligand and its steric interactions with the capping phenylphosphinidene group.     

Hydroalumination of Thioacetylenes: A Versatile Generation and Reactions of α-Aluminate Sulfides Intermediates

Hydroalumination of thioacetylenes using DIBAL-H and lithium di-(isobutyl)-n-(butyl)-aluminate hydride (Zweifel's reagent), followed by addition of water, furnished exclusively the (Z)- and ( E )-vinyl sulfides, respectively. The regio- and stereochemistry of the intermediates generated, (Z)- and ( E )-phenylthio vinyl alanates, were determined by capture with iodine, which afforded the corresponding ( E )- and (Z)-1-iodo-1-phenylthio-2-organoyl ethenes. Reactions of the ( E )-iodo(thio)ketene acetals with n-BuLi followed by addition of hexanal afforded the (Z)-phenylthio allylic alcohol, while the (Z)-iodo(thio)ketene acetals under similar reactions conditions gave the ( E )-phenylthio allylic alcohol exclusively.     

Chemo- and Regioselective 1,3-Dipolar Cycloaddition of 2-Diazopropane over 1,4-Benzoquinone: Synthesis of New Pyrazoloquinones

Abstract

1,3-Dipolar cycloaddition reaction of 2-diazopropane 1 with 1,4-benzoquinone 2 carried out at ?20 °C led to a minor mono-cycloadduct 4 and mixture of bis-cycloadducts 6 and 7. The same addition realized with 3H-pyrazole 7 at ?60 °C for 2 h yields a mixture of compounds 8 and 9 and results in O-alkylation. The reaction of 3H-pyrazoles 4 and 7 with dimethylsulfoxide and oxalyl chloride under Swern conditions led to pyrazolenines 11 and 12.     

Synthesis of functionalized tetrahydroisoquinolines via palladium-catalyzed 6-exo-dig carbocyclization of 2-bromo-N-propargylbenzylamines

An efficient twostep synthetic strategy for tetrahydroisoquinolines has been described. The first step involves CuI catalyzed three-component coupling reaction of terminal alkyne, aldehyde and amine that provides the requisite propargyl amine. Regio- and stereoselective palladium-catalyzed 6-exo-dig carbocyclization of propargyl amine, which provides a concise access to functionalized tetrahydroisoquinolines in good yields has been developed.     

Electrophilic Reactions of Dithio-Substituted o-Methoxycinnamyllithium

The dithio-substituted o-methoxycinnamyllithium 3L reacted at the α-site with D₂O and most of carbonyl compounds in extents of 70–100 %. while it reacted with halides at either the α or γ-site, depending on the nature of respective halide.