Journal ArticleDOI
1,3-Dipolar additions involving allenes: A density functional study of concerted and stepwise mechanisms
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TLDR
In this article, the 1,3-dipolar cycloadditions of allene with diazomethane, nitrile oxide and nitrone were investigated using DFT calculations at B3LYP/6-31G(d) level.Abstract:
Structures and energetics of reactants, transition structures, diradical intermediates and products of the 1,3-dipolar cycloadditions of allene with diazomethane, nitrile oxide and nitrone, have been investigated using DFT calculations at B3LYP/6-31G(d) level and the entire reaction surface has been explored. Two pathways are open for these reactions leading to two regiochemical products and in each way, the reaction can proceed in concerted or stepwise manner. In the stepwise process, there are two modes of attack, one leading to an allylic intermediate and the other an anti intermediate. A thorough search and analysis of these reaction paths show that stepwise modes are preferred over concerted modes, and regio 1 reaction prefers a stepwise path that involves a gauche intermediate whereas regio 2 reaction follows a stepwise path where an allylic intermediate is formed. Mainly the heteroatomic influence on the stability of diradical intermediates and other species in the reaction path and the cumulenic strain on allene determine the mechanism. Above factors also explain greater stability of allylic TS of regio 2 reaction compared to anti TS of regio 1 reaction, and this in turn explains the observed regioselectivity of the allene–diazomethane reaction. Computed deformation energies and bond orders establish that the favoured transition states are reactant-like and hence involve lower activation energies.read more
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Asymmetric 1,3-dipolar cycloadditions of acrylamides
Marie Kissane,Anita R. Maguire +1 more
TL;DR: This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol.
Journal ArticleDOI
Allenes and computational chemistry: from bonding situations to reaction mechanisms
Elena Soriano,Israel Fernández +1 more
TL;DR: The contents of this review span from the most fundamental studies on the equilibrium structure and chirality of allenes to recent advances in the study of complex reaction mechanisms involving allene derivatives in organometallic chemistry.
Journal ArticleDOI
Understanding the kinetic solvent effects on the 1,3‐dipolar cycloaddition of benzonitrile N‐oxide: a DFT study
TL;DR: The Journal of PHYSICAL ORGANIC CHEMISTRY (JUILLET 2011) as discussed by the authors ) is a journal dedicated to the study of chemical and biological sciences.
Journal ArticleDOI
An analysis of the regioselectivity of 1,3-Dipolar cycloaddition reactions of benzonitrile N-Oxides based on global and local electrophilicity and nucleophilicity indices
TL;DR: In this article, the global and local nucleophilicity and electrophilicity reactivity indices defined within the conceptual DFT were analyzed for the 1,3-dipolar cycloaddition (13DC) reactions of benzonitrile N-oxides (BNOs) with electrophilic and nucleophilic alkenes.
Journal ArticleDOI
Diels-Alder reactions of allene with benzene and butadiene: concerted, stepwise, and ambimodal transition states.
Hung V. Pham,Kendall N. Houk +1 more
TL;DR: Multiconfigurational complete active space methods (CASSCF and CASPT2) were used to investigate the (4 + 2) cycloadditions of allene with butadiene and with benzene to determine the mechanism of the Diels–Alder reactions with an allene dienophile.
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Some reasons not to use spin projected density functional theory
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