Substituent effect on the [2 + 3] cycloaddition of (E)‐β‐Nitrostyrene with (Z)‐C,N‐Diarylnitrones

Abstract

The kinetics of the title reaction were studied in toluene at 80 °C by means of HPLC. The overall rate constant (ktotal) of the reaction of (E)‐β‐nitrostyrene (1) with (Z)‐C‐phenyl‐N‐arylnitrones (2a–g) was found to increase with increasing Hammett σ‐constant, whereas in the case of (Z)‐C‐aryl‐N‐phenylnitrones (2g–p) and the same nitrostyrene the rate decreased. The substituent effect in these reactions is inconsistent with FMO treatments of cycloaddition rates. For both reaction series good linear relationships were obtained between log ktotal and the net charge on the carbon atom in the >CN(O)— moiety of the nitrones calculated by the AM1 method. Copyright © 2001 John Wiley & Sons, Ltd.

A DFT study on the (2 + 3) cycloaddition reactions of 2‐nitropropene‐1 with Z‐C, N‐diarylnitrones

“…Within the continuation of our studies of [4 þ 2]p-electron cycloaddition reactions of conjugated nitroalkenes, [1][2][3][4][5][6][7] this paper presents quantum-mechanical simulation of competing (2 þ 3) cycloaddition pathways for 2-nitropropene-1 (1) to a homogenous series of Z-C,N-diarylnitrones (2a-e) which differ in substituents in phenyl rings. Theoretically, the reactions may yield stereo-and regioisomeric diarylmethylnitroisoxazolidines (3a-e-6a-e) (Scheme).…”

“…We successfully pursued a similar approach earlier for the analysis of the mechanism of the (2 þ 3) cycloaddition of Z-C,N-diphenylnitrone to b-nitrostyrene and 3,3,3-trichloro-1-nitropropene-1 [3] achieving satisfactory correlation with experimental data. [2,4,6,7] (www.interscience.wiley.com) DOI 10.1002/poc.1505 Table 1. Essential molecular properties from the B3LYP/6-31G * calculations of critical structures for (2 þ 3) cycloaddition of 2-nitropropene-1 1 to Z-C,N-diarylnitrones 2a-e…”

Copper(I)-Catalyzed 1,3-Dipolar Cycloaddition of Ketonitrones to Dialkylcyanamides: A Step toward Sustainable Generation of 2,3-Dihydro-1,2,4-oxadiazoles

“…Literature data confirm our observations and, indeed, CAs of nitrones often belong to group II reactions, 28 but it is easily possible to change the type of reaction by the variation of substituents in the reactants or its coordination to the metal center. Thus, CA of nitrones to electron-deficient dipolarophiles (namely, acrylonitrile, 29 acrolein, 30 methyl propiolate, 31 methyl acrylate, 32 nitroalkenes, 33 fluoroalkenes, and fluoroalkynes 34 ) as well as metal-involving processes 35 is determined by the interaction of HOMO dipole –LUMO dipolarophile (group I, normal electron demand reactions), whereas usage of dipolarophiles with electron-donating substituents (e.g., methyl vinyl ether) 26a leads to switching of the type of reaction to inverse electron demand (HOMO dipolarophile –LUMO dipole , group III by Sustmann’s classification).…”