Controlling Selectivity for Cycloadditions of Nitrones and Alkenes Tethered by Benzimidazoles: Combining Experiment and Theory

Meng, Liping; Wang, Selina C.; Fettinger, James C.; Kurth, Mark J.; Tantillo, Dean J.

doi:10.1002/ejoc.200801211

Cited by 10 publications

(4 citation statements)

References 45 publications

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“…S4. † It should be mentioned here that in recent times E-Z isomerization studies 64,65 on different types of nitrones have been extensively reported at the DFT level of calculations.…”

Section: Optimized Transition States On the Excited State And Ground ...mentioning

confidence: 99%

A comprehensive spectroscopic investigation of α-(2-naphthyl)-N-methylnitrone: a computational study on photochemical nitrone–oxaziridine conversion and thermal E–Z isomerization processes

Saini

Chattopadhyay

2015

RSC Adv.

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This comprehensive spectroscopic analysis of a-(2-naphthyl)-N-methylnitrone has proposed its photochemical oxaziridine formation and thermal E-Z isomerization mechanisms. The activation energy for the conversion of the unstable non-planar E isomer to the stable planar Z-isomer is found to be 23.7 kcal mol À1 at the CASSCF/6-31G* level of calculation. A transition state with a negative frequency of 350 cm À1 is likely to be responsible for this process. Both CASSCF and ONIOM-based studies have revealed that the nitrone-oxaziridine photochemical conversion involves non-radiative decay channels which include biradicaloid conical intersection (CI) points through Hula-twist and terminal one-bond-flip motions, situated at 35-40 kcal mol À1 below the first excited singlet state (S 1 ). Following the directions of their gradient-difference vectors, the optimized oxaziridine geometries are obtained. The nature of the low-lying singlet-singlet transitions of these a-naphthyl N-methylnitrones is found to be similar to that of the conjugated non-polar polyenes, and differs appreciably from our previously studied longchain conjugated nitrone systems. The fluorescent S 1 state with a radiative lifetime of nanosecond order is populated by the weak upward S 0 -S 1 transition (transition moment: 0.3 Debye) and through the decay of the S 2 state, which eventually gets involved in the S 0 /S 1 conical intersections.

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“…S4. † It should be mentioned here that in recent times E-Z isomerization studies 64,65 on different types of nitrones have been extensively reported at the DFT level of calculations.…”

Section: Optimized Transition States On the Excited State And Ground ...mentioning

confidence: 99%

A comprehensive spectroscopic investigation of α-(2-naphthyl)-N-methylnitrone: a computational study on photochemical nitrone–oxaziridine conversion and thermal E–Z isomerization processes

Saini

Chattopadhyay

2015

RSC Adv.

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“…Kurth, Tantillo and co‐workers undertook a combined experimental/theoretical study on tethered nitrone/alkene cycloaddition reactions, with the goal of controlling regioselectivity and thereby allowing access to molecular frameworks with significantly different shapes (Scheme ) 14. Quantum chemical calculations were used to rationalize initial experimental results, which led to subsequent computational predictions on systems that might have improved regioselectivity.…”

Section: Optimizing Selectivitymentioning

confidence: 99%

The Many Roles of Quantum Chemical Predictions in Synthetic Organic Chemistry

Nguyen¹,

Tantillo²

2013

Chemistry An Asian Journal

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“…Tantillo, Kurth and co-workers performed a combined experimental/theoretical study on the effects of substituents on regio-and stereoselectivity in intramolecular 1,3-dipolar cycloadditions of nitrones and alkenes tethered by benzimidazoles (Scheme 18). 24 B3LYP calculations were employed to help rationalize the regio-and stereoselectivity observed in initial experiments, and the success of this approach then led to predictions of product distributions for additional reactions, which were then tested experimentally. Overall, it was concluded that, by employing a large substituent at position R 2 or R 3 , complete selectivity can be achieved for either the fused (B) or bridged (A) cycloadduct, respectively.…”

Section: Scheme 16mentioning

confidence: 99%

Reaction mechanisms : Part (ii) Pericyclic reactions

Lee

Tantillo

2010

Annu. Rep. Prog. Chem., Sect. B: Org. Chem.

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This report surveys the 2009 literature on mechanisms of pericyclic reactions. Again, mechanistic studies of cycloadditions dominate, especially those of relevance to organic synthesis. Several electrocyclizations used in the synthesis of complex polycycles were also examined in detail, as were a number of sigmatropic shifts involving aza-polyenes. General theories and theoretical toolsGouverneur and co-workers provided a thorough review of pericyclic reactions involving fluoroorganic compounds, highlighting the synthetic utility of these reactions and both experimental and theoretical studies on their mechanisms with a focus on the effect of fluorine on their regio-and stereoselectivities. 1 Mandado and Ponec described the application of their multicenter bond indices to pericyclic reactions, 2 focusing in this report on electrocyclizations. The authors suggested that computed multicenter bond indices correlate with allowedness of pericyclic reactions and are likely to be applicable to other classes of pericyclic reactions. Cycloaddition reactions [4+2] ReactionsSantos and co-workers used quantum chemical calculations (MP2 and B3LYP) and NMR experiments to reexamine the mechanism of AlR 3 -promoted Diels-Alder reactions that employ dienophiles bearing the Evans chiral auxiliary (e.g., Scheme 1). 3 The authors concluded that models for the origins of stereoselectivity involving species in which Al bridges between the two carbonyl oxygens do not necessarily correspond to what actually occurs. Instead, the authors argued for the involvement of species in which Al is not chelated.

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Controlling Selectivity for Cycloadditions of Nitrones and Alkenes Tethered by Benzimidazoles: Combining Experiment and Theory

Cited by 10 publications

References 45 publications

A comprehensive spectroscopic investigation of α-(2-naphthyl)-N-methylnitrone: a computational study on photochemical nitrone–oxaziridine conversion and thermal E–Z isomerization processes

A comprehensive spectroscopic investigation of α-(2-naphthyl)-N-methylnitrone: a computational study on photochemical nitrone–oxaziridine conversion and thermal E–Z isomerization processes

The Many Roles of Quantum Chemical Predictions in Synthetic Organic Chemistry

Reaction mechanisms : Part (ii) Pericyclic reactions

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