Center for Magnetic Resonance

V.A. Rassadin, A.A. Yakimanskiy, E.V. Eliseenkov, V.P. Boyarskiy
“Synthesis of acyclic diaminocarbene palladium complex featuring triethoxysilane moiety”

Inorg. Chem. Comm., 2015, 2015, 61, 21-23
DOI:10.1016/j.inoche.2015.08.008

The first example of an acyclic diaminocarbene palladium complex, viz. cis-[PdCl₂(CN(2,6-Me₂C₆H₃)){C(NH(2,6-Me₂C₆H₃)) = NH(CH₂)₃Si(OEt)₃}], featuring the triethoxysilane moiety is described. The complex was generated from bis(o-xylylisocyanide)palladium dichloride and (3-aminopropyl)triethoxysilane under mild conditions and isolated in 88% yield. The target compound is stable at RT either in the solid state or in CDCl₃ or CD₃OD solutions within several months.

D.S. Bolotin, M.Ya. Demakova, A.S. Novikov, M.S. Avdontceva, M.L. Kuznetsov, N.A. Bokach, V.Yu. Kukushkin
“Bifunctional Reactivity of Amidoximes Observed upon Nucleophilic Addition to Metal-Activated Nitriles”

Inorg. Chem., 2015, 54, 4039-4046
DOI:10.1021/acs.inorgchem.5b00253

Treatment of the aromatic nitrile complexes trans-[PtCl₂(RC₆H₄CN)₂] with the aryl amidoximes p-R′C₆H₄C(NH₂)═NOH, followed by addition of 1 equiv of AgOTf and then 5 equiv of Et₃N, leads to the chelates [PtCl{HN═C(RC₆H₄)ON═C(C₆H₄R′-p)NC(RC₆H₄)═NH}] (15 examples; yields 71−88% after column chromatography) derived from the platinum(II)-mediated coupling between metal-activated nitriles and amidoximes. The combined experimental and theoretical results indicate that the coupling with the nitrile ligands involves both the HON and monodeprotonated NH₂ groups of the amidoximes.

V.A. Rassadin, V.P. Boyarskiy, V.Yu. Kukushkin
“Facile Gold-Catalyzed Heterocyclization of Terminal Alkynes and Cyanamides Leading to Substituted 2-Amino-1,3-Oxazoles”

Org. Lett., 2015, 17, 3502-3505
DOI:10.1021/acs.orglett.5b01592

Facile gold-catalyzed heterocyclization based upon intermolecular trapping of the generated α-oxo gold carbenes with various cyanamides R²R³NCN (R²/R³ = Alk/Alk, −(CH₂)₂O(CH₂)₂–, Ar/Ar, Ar/H) has been developed. In most cases, 2-amino-1,3-oxazoles functionalized at the nitrogen atom as well as at the fifth position of the heterocyclic ring (12 examples) were isolated in good to moderate yields.

I.A. Smetanin, M.S. Novikov, N.V. Rostovskii, A.F. Khlebnikov, G.L. Starova, D.S. Yufit
“4-Halo-2-azabuta-1,3-dienes as intermediates in the rhodium carbenoid-initiated transformation of 2-halo-2H-azirines into 2,3-dihydroazetes and 2,5-dihydrooxazoles”

Tetrahedron, 2015, 71, 4616-4628
DOI:10.1016/j.tet.2015.05.022

A wide range of electron-poor 4-bromo-/4-chloro-2-azabuta-1,3-dienes were synthesized by the Rh2(OAc)4-catalyzed reaction of diazo esters and diazo ketones with methyl 2-halo-2H-azirine-2-carboxylates. The E stereoselectivity with respect to the configuration of the Cdouble bond; length as m-dashC bond of the 2-azadiene moiety is in good agreement with the results of DFT (M06-2X/6-31+G(d,p)) calculations of the reaction pathway. The reaction proceeds via the formation of an azirinium ylide intermediate followed by ring opening with outward rotation of the halogen atom. Depending on the substitution pattern at C1 electron-poor 4-halo-2-azabutadienes can undergo two types of cyclization at elevated temperatures: reversible 1,4-electrocyclization to give 2,3-dihydroazetes or 1,5-exo-trig cyclization to give 5-methylene-2,5-dihydrooxazoles, both in good yields. The dihydrooxazole derivatives can be also obtained at ambient temperature under DBU catalysis.

E.E. Galenko, O.A. Tomashenko, A.F. Khlebnikov, M.S. Novikov
“Metal/organo relay catalysis in a one-pot synthesis of methyl 4-aminopyrrole-2-carboxylates from 5-methoxyisoxazoles and pyridinium ylides”

Org. Biomolec. Chem., 2015, 13, 9825-9833
DOI:10.1039/c5ob01537e

Methyl 4-aminopyrrole-2-carboxylates were synthesized in one-pot mode by the relay catalytic cascade reaction of 5-methoxyisoxazoles with pyridinium ylides by the use of a FeCl₂/Et₃N binary catalytic system leading to 1-(5-methoxycarbonyl-1H-pyrrol-3-yl)pyridinium salts followed by hydrazinolysis. The approach permits the introduction of a substituent at the pyrrole nitrogen via a nucleophilic reaction of the pyrrolylpyridinium ylide derived from the salt. Catalytic reduction of the ylides gives methyl 4-piperidinopyrrole-2-carboxylates.

N.V. Rostovskii, P.A. Sakharo, M.S. Novikov, A.F. Khlebnikov, G.L. Starova

“Cu(I)-NHC-Catalyzed (2+3)-Annulation of Tetramic Acids with 2H-Azirines: Stereoselective Synthesis of Functionalized Hexahydropyrrolo[3,4-b]pyrroles”

Org. Lett., 2015, 17, 4148-4151
DOI:10.1021/acs.orglett.5b01883

A stereoselective and high-yield synthesis of hexahydropyrrolo[3,4-b]pyrroles from tetramic acids and 2H-azirines under Cu(I)–NHC catalysis is developed. An unusual N–C2 azirine bond cleavage, initiated by a copper enolate, was rationalized in terms of a free radical reaction mechanism.