26465-83-8Relevant academic research and scientific papers
Transition-Metal Catalyzed Stereoselective γ-Arylation and Friedel-Crafts Alkylation: A Concise Synthesis of Indenes
Ramesh, Karu,Satyanarayana, Gedu
supporting information, p. 3235 - 3242 (2020/06/02)
A highly stereoselective [Pd]-catalyzed arylation of tert-alkenols, is presented and applied to the synthesis of indenes using intramolecular Friedel–Crafts alkylation sequence. The initial Heck reaction is performed by using water as the green solvent. A simple acid triggers intramolecular alkylation in short reaction times at room temperature. Notably, indenes have been accomplished using a single column chromatography technique.
Mechanisms of the PtCl2-catalyzed intramolecular cyclization of o -isopropyl-substituted aryl alkynes for the synthesis of indenes and comparison of three sp3 C-H bond activation modes
Wang, Yi,Liao, Wei,Huang, Genping,Xia, Yuanzhi,Yu, Zhi-Xiang
, p. 5684 - 5696 (2014/07/08)
Chatani and He respectively reported an efficient way to synthesize indenes through PtCl2 catalyzed sp3 C-H bond activation. Interestingly, the R group (R = H or Br) in the alkyne moiety of the substrates in Chatanis experiments migrates to the C3 position in indenes, whereas the R group (R = Ar) stays in the original C2 position of final indenes in Hes experiments. DFT calculations indicated that there are two competing pathways a and c for the cyclization reaction. Pathway a involves [1,2]-R migration, [1,5]-H shift, and 4π-electrocyclization, giving the indenes with the R group at the C3 position. Pathway c takes place through irreversible [1,5]-H shift/cyclization and [1,2]-H shift, generating indenes with the R group at the C2 position. DFT calculations found that, when R = H or Br, pathway a is favored. When R = alkyl group, the [1,2]-R migration is difficult and pathway c is preferred. When R = Ar, DFT calculations predicted and experiments verified that both pathways a and c occur to give two indene products. Comparison of different models of sp3 C-H activations has been presented to guide further understanding and prediction of new C-H bond activations.
Organometallic compounds of group III. XXXIV. Steric factors in the carbalumination of olefins. The question of the anomalous, reduced reactivity of olefins versus acetylenes.
Eisch, John J.,Burlinson, Nicholas E.,Boleslawski, Marek
, p. 137 - 152 (2007/10/05)
In order to understand the reasons for the anomalous, reduced reactivity of olefins toward electrophilic carbalumination, compared with that of acetylenes, the reactivity, stereochemistry and regiochemistry of a series of acyclic and cyclic olefins in carbalumination with triphenylaluminum were investigated. The following substrates underwent reaction between 80 and 225°C with decreasing ease in the order: norbornadiene > cis-β-methylstyrene > trans-β-methylstyrene ～ 1,2-dihydronaphthalene ～ 1,1-dimethylindene > cis-1,2-diphenylethylene > 3,3,3-triphenylpropene > trans-1,2-diaryethylenes ～ phenylcyclopropanes. The stereochemistry of the mono- and bis-carbaluminations of norbornadiene was shown to be syn, exo. The regiochemistry observed with unsymmetrical olefins could readily be rationalized by a steric effect operative in the preferential collapse of an olefin-(C6H5)3Al π-complex. Besides carbalumination, several other reactions were observed with these olefins: (1) cis, trans-isomerization of acyclic olefins; (2) metallation of vinylic carbon atoms by (C6H5)3Al; (3) elimination of (C6H5)2AlH from carbalumination adducts; (4) by inference from the foregoing reaction with certain systems, epimerization at sp3-hybridized carbon-aluminum bonds; and (5) decarbalumination with carbon-carbon bond scission. These side reactions were considered together with relative reactivities, stereochemistry and regiochemistry in developing energy profiles for the carbalumination of olefins and acetylenes. The reduced reactivity of olefins is thought to arise from steric factors that destabilize a π-complex-with (C6H5)3Al and that cause a trapezoidal-like transition state to be of higher energy and rate-determining. The higher reactivity of acetylenes is ascribed to less steric hindrance both to π-complexation with (C6H5)3Al, and to the collapse of the complex via a trapezoidal configuration. For acetylenes, it is judged that the formation of an intimate π-complex is rate-determining.
