82414-24-2Relevant academic research and scientific papers
Rate enhancement of 1,3-dipolar cycloaddition of N-methylindole: The singular role of Grignard reagents
Benincori, Tiziana,Sannicolo, Franco,Trimarco, Licia,Bonati, Laura,Grandi, Stefania,Pitea, Demetrio,Gatti, Carlo
, p. 455 - 466 (2007/10/03)
The reactions of 2-N-methylindolyl and 2- and 3-benzo [b]thiophenyl anions with nitrile oxides and nitrilimines were performed in order to investigate whether the use of anionic dipolarophiles modifies a classical 1,3-dipolar cycloaddition. When lithium compounds were used as bases, the heterocyclic anions invariably acted as nucleophilic species; in contrast, when a Grignard reagent was employed, the N-methylindole gave cycloaddition products with an extraordinary rate enhancement. The hypothesis that N-methylindole and ethylmagnesium bromide give an adduct much more reactive than N-methylindole itself was supported by the results of a theoretical investigation. The structure and electron distribution of the adduct were determined by ab initio calculations and compared with those of known Grignard complexes with nitrogen ligands. The performance of different basis sets was tested. The quantum theory of atoms in molecules was used to determine atomic charges and to describe the nature of bonds in terms of the properties of the electron density at the bond critical points.
SELECTIVITY IN CYCLOADDITIONS-IX CYCLOADDITIONS OF NITRILE OXIDES TO INDOLES. REACTIVITY AND REGIOCHEMISTRY
Caramella, P,Corsico, A. Coda,Corsaro, A,Del Monte, D.,Albini, F. Marinone
, p. 173 - 182 (2007/10/02)
Cycloadditions of benzonitrile oxide and mesitonitrile oxide to N-methylindole and indole yield the acid sensitive cycloadducts 1 a-d with high regioselectivity.With N-carbethoxyindole the stable cycloadducts 1 e,f and minor amounts of the regioisomeric 2 e,f are isolated.The electron withdrawing substituent reduces both the regioselectivity and the reactivity of the cycloadditions.Frontier orbital considerations, based on MINDO/3 calculations, allow elucidation of the observed changes in reactivity and regiochemistry.
