Twisted Push-Pull Alkenes Bearing Geminal Cyclicdiamino and Difluoroaryl Substituents

The systematic combination of N-heterocyclic olefins (NHOs) with fluoroarenes resulted in twisted push-pull alkenes. These alkenes carry electron-donating cyclicdiamino substituents and two electron-withdrawing fluoroaryl substituents in the geminal positions. The synthetic method can be extended to a variety of substituted push-pull alkenes by varying the NHO as well as the fluoroarenes. Solid-state molecular structures of these molecules reveal a notable elongation of the central C-C bond and a twisted geometry in the alkene motif. Absorption properties were investigated with UV-vis spectroscopy. The redox properties of the twisted push-pull alkenes were probed with electrochemistry as well as UV-vis/NIR and EPR spectroelectrochemistry, while the electronic structures were computationally evaluated and validated.Fil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Universitat Stuttgart; AlemaniaFil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Pal, Sudip. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Universität Stuttgart; AlemaniaFil: Chandrasekhar, Vadapalli. Indian Institute Of Technology Kanpur; IndiaFil: Jana, Anukul. Tata Institute Of Fundamental Research, Hyderabad; Indi

Trisubstituted Geminal Diazaalkenes Derived Transient 1,2-Carbodications

Coulombic repulsion between two adjacent cation centres of 1,2-carbodications are known to decrease with π- and/or n-donor substituents by the positive charge delocalization. Here we report the delocalization of positive charge of transient 1,2-carbodications having one H-substituent by an intramolecular base-coordination. N-heterocyclic olefin (NHO) derived 2-pyrrolidinyl appended trisubstituted geminal diazaalkenes were employed for the generation of transient 1,2-carbodications through a 2-e chemical oxidation process. We have also studied the 1-e oxidation reaction of trisubstituted geminal diazaalkenes (electrochemically and chemically) and also studied them by in situ EPR spectroscopy.Fil: Mandal, Debdeep. Indian Institute of Technology; IndiaFil: Stein, Felix. Freie Universität Berlin; AlemaniaFil: Chandra, Shubhadeep. Universitat Stuttgart;Fil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Sarkar, Pallavi. Indian Institute of Technology; IndiaFil: Das, Shubhajit. Indian Institute of Technology; IndiaFil: Kundu, Abhinanda. Indian Institute of Technology; IndiaFil: Sarkar, Arighna. Indian Institute of Technology; IndiaFil: Rawat, Hemant. Indian Institute of Technology; IndiaFil: Pati, Swapan. Indian Institute of Technology; IndiaFil: Chandrasekhar, Vadapalli. Indian Institute of Technology; IndiaFil: Sarkar, Biprajit. Universität Stuttgart;Fil: Jana, Anukul. Indian Institute of Technology; Indi

Activation of Aromatic C‐F Bonds by a N‐Heterocyclic Olefin (NHO)

A N-heterocyclic olefin (NHO), a terminal alkeneselectively activates aromatic C-F bonds without the need of anyadditional catalyst. As a result, a straightforward methodology wasdeveloped for the formation of different fluoroaryl substituted alkenesin which the central carbon-carbon double bond is in a twistedgeometry.Fil: Mandal, Debdeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandra, Shubhadeep. Freie Universität Berlin.; AlemaniaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mahata, Alok. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Sarkar, Arighna. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kundu, Abhinanda. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Anga, Srinivas. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Rawat, Hemant. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Schulzke, Carola. ERNST MORITZ ARNDT UNIVERSITÄT GREIFSWALD (UG);Fil: Sarkar, Biprajit. Freie Universität Berlin.; AlemaniaFil: Mote, Kaustubh R.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Chandrasekhar, Vadapalli. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Jana, Anukul. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ

Propargylic C(sp³)–H Bond Activation for Preparing η³‑Propargyl/Allenyl Complexes of Yttrium

Propargylic C­(sp³)H bond activation of 1-substituted-1-propynes, such as 1-trimethylsilyl-1-propyne, 2-hexyne, and 1-phenyl-1-propyne, was achieved by treatment with an alkylyttrium complex <b>8</b> bearing an ene-diamido ligand to give the corresponding (η³-propargyl/allenyl)yttrium complexes <b>7a</b>–<b>c</b>. A unique delocalized η³-propargyl/allenyl structure of these three complexes was revealed by NMR spectroscopy and X-ray single crystal analyses. To elucidate the reactivity of the η³-propargyl/allenyl unit of complexes <b>7a</b>–<b>c</b>, we conducted two reactions with <i>N</i>-methylaniline and <i>N</i>,<i>N</i>′-dicyclohexylcarbodiimine. For protonation by <i>N</i>-methylaniline, we found that the product distribution of monosubstituted internal alkynes and allenes depended on the substituent on the η³-propargyl/allenyl moiety: <b>7a</b> and <b>7b</b> afforded the corresponding internal alkynes as the major products, whereas the major protonation product of <b>7c</b> was phenylallene. For the insertion of <i>N</i>,<i>N</i>′-dicyclohexylcarbodiimine, complex <b>7a</b> selectively yielded η³-{<i>N</i>,<i>N</i>′-dicyclohexyl-2-(3-trimethylsilylpropargyl)­amidinate}yttrium <b>12a</b>, while complex <b>7c</b> produced η³-{<i>N</i>,<i>N</i>′-dicyclohexyl-2-(1-phenylallenyl)­amidinate}­yttrium complex <b>13c</b>, though complex <b>7b</b> gave a mixture of η³-{<i>N</i>,<i>N</i>′-dicyclohexyl-2-(3-normalpropylpropargyl)­amidinate}­yttrium complex <b>12b</b> and η³-{<i>N</i>,<i>N</i>′-dicyclohexyl-2-(1-normalpropylallenyl)­amidinate}yttrium <b>13b</b> in an 83:17 ratio. On the basis of the product distributions in these two-types of reactions, (η³-propargyl/allenyl)­yttrium complexes were shifted into preferentially favorable η¹-allenyl species or η¹-propargyl species depending on the substituents prior to the reaction with electrophiles via a four-membered cyclic mechanism

Direct <i>ortho</i>-C–H Aminoalkylation of 2‑Substituted Pyridine Derivatives Catalyzed by Yttrium Complexes with <i>N,N′</i>-Diarylethylenediamido Ligands

A mixed ligated amidoyttrium complex, Y­(NBn₂)­(<b>L1</b>)­(THF)₂ (<b>8</b>, L1 = <i>N</i>,<i>N’</i>-bis­(2,6-diisopropylphenyl)­ethylenediamine), served as a catalyst for addition of the <i>ortho</i>-pyridyl C­(sp²)H bond of 2-substituted pyridines to nonactivated imines; complex <b>8</b> showed superior catalytic performance compared with Y­[N­(SiMe₃)₂]₃ (<b>1</b>) and Y­[N­(SiMe₃)₂]₂(NBn₂)­(THF) (<b>2</b>). Concerning the reaction mechanism, we conducted a stoichiometric reaction of an alkylyttrium complex, Y­(CH₂SiMe₃)­(<b>L1</b>)­(THF)₂ (<b>7</b>), with 2-ethylpyridine (<b>4e</b>), giving a mixture of (η³-pyridylmethyl)yttrium complex <b>9</b> and (η²-pyridyl)yttrium complex <b>10</b> along with elimination of SiMe₄. Furthermore, addition of <i>N</i>-(<i>tert</i>-butyl)-2-methylpropan-1-imine (<b>5i</b>) to the mixture of <b>9</b> and <b>10</b> afforded (pyridylmethylamido)yttrium complex <b>11</b> as a single product, and the catalytic activity of <b>11</b> was comparable to that of complex <b>8</b>. Kinetic analysis of the aminoalkylation reaction in the presence/absence of HNBn₂ revealed that the reaction rate in the presence of HNBn₂ was four times faster than that without HNBn₂ due to acceleration of the product-eliminating step from complex <b>11</b> by HNBn₂ to regenerate amidoyttrium complex <b>8</b> and the product. In addition, we determined that the catalytic reaction obeyed a first-order rate dependence on the catalyst concentration, independent of the imine concentration, and a second-order rate dependence on the concentration of the pyridine substrate in the reaction system, both with and without HNBn₂. An enantiomerically pure <i>N</i>,<i>N’</i>-diaryl-1,2-diphenylethylenediamido ligand was applied for the C­(sp²)H aminoalkylation reaction in combination with Lu­(CH₂SiMe₃)₃(THF)₂ to give chiral aminoalkylated products in moderate yield with good enantioselectivity

Facile One‐Pot Assembly of Push–Pull Imines by a Selective C–F Substitution Process in Aryl Fluorides

Herein, we report the synthesis of a series of push–pull imines by considering cyclic diamino substituent at the C‐centre and fluoroaryl substituent at the N‐centre. This has been achieved by a selective aromatic nucleophilic substitution of different fluoroarenes by N‐H‐substituted N‐heterocyclic imines (NHIs) at ambient conditions without any additional reagent. Solid‐state molecular structure analysis reveals the elongation of the central C–N bond of the imine functionality, which is consistent with the push–pull nature of these imines. The push–pull nature of these imines is further validated by computational studies