Direct observation of denitrogenation process of 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH) derivatives, using a visible 5-fs pulse laser

Abe, Manabu; Iwakura, Izumi; Yabushita, Atsushi; Yagi, Shingo; Li, Jun; Okamura, Kotaro; Kobayashi, Takayoshi

doi:10.1016/j.cplett.2012.01.024

Cited by 9 publications

(15 citation statements)

References 31 publications

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“…The fate of singlet diradicals with p single-bonding character was not to produce the trans-configured ring-closed products, but to produce the cis-configured ring-closed compounds. [25] The kinetically controlled cis-configured products were not directly observed by NMR spectroscopic analyses owing to the shortlived character of the cis isomers. The steric interaction between the alkoxy group and the phenyl ring, which determines the energy barrier of the ring-closing reaction, was found to play a crucial role in determining the lifetime of the singlet-state molecules.…”

Section: Resultsmentioning

confidence: 99%

Kinetic Stabilization and Reactivity of π Single‐Bonded Species: Effect of the Alkoxy Group on the Lifetime of Singlet 2,2‐Dialkoxy‐1,3‐diphenyloctahydropentalene‐1,3‐diyls

Nakagaki

Sakai

Mizuta

et al. 2013

Chemistry A European J

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Kinetic stabilization and reactivity of π single-bonded species have been investigated in detail by generating a series of singlet 2,2-dialkoxy-1,3-diphenyloctahydropentalene-1,3-diyls (DRs). The lifetime at 293 K in benzene was found to increase when the carbon chain length of the alkoxy groups was increased; 292 ns (DRb; OR = OR' = OCH3) <880 ns (DRc; OR = OR' = OC2H5) <1899 ns (DRd; OR = OR' = OC3H7) ≈2292 ns (DRe; OR = OR' = OC6H13) ≈2146 ns (DRf; OR = OR' = OC10H21). DRh (OR = OC3H7, OR' = OCH3; 935 ns) with the mixed-acetal moiety is a longer-lived species than another diastereomer DRg (OR = OCH3, OR' = OC3H7; 516 ns). Activation parameters determined for the first-order decay process reveal that the enthalpy factor plays a crucial role in determining the energy barrier of the ring-closing reaction, that is, from the π-bonding to the σ-bonding compounds. Computational studies using density functional theory provided more insight into the structures of the singlet species with π single-bonded character and the transition states for the ring-closing reaction, thereby clarifying the role of the alkoxy group on the lifetime and the stereoselectivity of the ring-closing reaction.

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Section: Resultsmentioning

confidence: 99%

Kinetic Stabilization and Reactivity of π Single‐Bonded Species: Effect of the Alkoxy Group on the Lifetime of Singlet 2,2‐Dialkoxy‐1,3‐diphenyloctahydropentalene‐1,3‐diyls

Nakagaki

Sakai

Mizuta

et al. 2013

Chemistry A European J

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“…3,18,20 This reaction pathway has been predicted to be endothermic when the system reaches the DBH-diyl diradical. At the same time, DBH-diyl has been proposed to be the intermediate species for the formation of the closed-shell bicycle[2.1.0]pentane (BCP-DBH).…”

Section: Resultsmentioning

confidence: 99%

“…In particular, the mechanism of denitrogenation for 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH) derivatives has been investigated using a visible 5 fs pulse laser. 3 There has been a long debate concerning a reasonable mechanism that describes this reaction because product formation could be achieved through a concerted or a stepwise mechanism. Thus, the process has been widely studied, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] establishing that the corresponding reaction mechanism for thermal denitrogenation depends on the nature of substituents at the methanobridge carbon atom of the DBH structure.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the process has been widely studied, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] establishing that the corresponding reaction mechanism for thermal denitrogenation depends on the nature of substituents at the methanobridge carbon atom of the DBH structure. 3,18,21,22 For electron donating substituents (X = -H and -SiR 3 ) the denitrogenation process takes place via concerted mechanisms, whereas s electron withdrawing substituents (X = -F and -OCH 2 CH 3 ) give rise to stepwise ones via diazenyl diradical intermediates. 3,18,21 The substituent effects have been explained based on computational studies in which the lowest electronic configuration of the singlet state of the resulting diradicals 18 has been invoked.…”

Section: Introductionmentioning

confidence: 99%

“…3,18,21,22 For electron donating substituents (X = -H and -SiR 3 ) the denitrogenation process takes place via concerted mechanisms, whereas s electron withdrawing substituents (X = -F and -OCH 2 CH 3 ) give rise to stepwise ones via diazenyl diradical intermediates. 3,18,21 The substituent effects have been explained based on computational studies in which the lowest electronic configuration of the singlet state of the resulting diradicals 18 has been invoked.…”

Section: Introductionmentioning

confidence: 99%

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Inquiry of the electron density transfers in chemical reactions: a complete reaction path for the denitrogenation process of 2,3-diazabicyclo[2.2.1]hept-2-ene derivatives

Safont

González-Navarrete

Oliva

et al. 2015

Phys. Chem. Chem. Phys.

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Q3 ndrésA detailed study on all stages associated with the reaction mechanisms for the denitrogenation of 2,3-diazabicyclo[2.2.1]hept-2-ene derivatives (DBX, with X substituents at the methano-bridge carbon atom, X = H and OH) is presented. In particular, we have characterized the processes leading to cycloalkene derivatives through migration-type mechanisms as well as the processes leading to cyclopentil-1,3-diradical species along concerted or stepwise pathways. The reaction mechanisms have been further analysed within the bonding evolution theory framework at B3LYP and M05-2X/6-311+G(2d,p) levels of theory. Analysis of the results allows us to obtain the intimate electronic mechanism for the studied processes, providing a new topological picture of processes underlying the correlation between the experimental measurements obtained by few-optical-cycle visible pulse radiation and the quantum topological analysis of the electron localization function (ELF) in terms of breaking/forming processes along this chemical rearrangement. The evolution of the population of the disynaptic basin V(N1,N2) can be related to the experimental observation associated with the NQN stretching mode evolution, relative to the N 2 release, along the reaction process. This result allows us to determine why the N 2 release is easier for the DBH case via a concerted mechanism compared to the stepwise mechanism found in the DBOH system. This holds the key to unprecedented insight into the mapping of the electrons making/breaking the bonds while the bonds change.

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A Critical Assessment of the Kinetics and Mechanism of Initiation of Radical Polymerization with Commercially Available Dialkyldiazene Initiators

Moad

2019

Progress in Polymer Science

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Direct observation of denitrogenation process of 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH) derivatives, using a visible 5-fs pulse laser

Cited by 9 publications

References 31 publications

Kinetic Stabilization and Reactivity of π Single‐Bonded Species: Effect of the Alkoxy Group on the Lifetime of Singlet 2,2‐Dialkoxy‐1,3‐diphenyloctahydropentalene‐1,3‐diyls

Kinetic Stabilization and Reactivity of π Single‐Bonded Species: Effect of the Alkoxy Group on the Lifetime of Singlet 2,2‐Dialkoxy‐1,3‐diphenyloctahydropentalene‐1,3‐diyls

Inquiry of the electron density transfers in chemical reactions: a complete reaction path for the denitrogenation process of 2,3-diazabicyclo[2.2.1]hept-2-ene derivatives

A Critical Assessment of the Kinetics and Mechanism of Initiation of Radical Polymerization with Commercially Available Dialkyldiazene Initiators

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