Theoretical study on the [4+2] cycloaddition of 1,3-dimethylindole with 2,6-dimethylquinone
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The [4+2] cycloaddition reaction of 1,3-dimethylindole and ortho-quinone methide (obtained from tautomerization of 2,6-dimethylquinone under basic conditions), experimentally studied by Wen and co-workers, was theoretically studied at the B3LYP/6-311G** and M062X/6-311G** computational levels in both gas and ethanol solution phases. Two possible reactive channels were considered between the reactants and their theoretical parameters were calculated. The results indicated that the formation of the experimentally reported product is clearly confirmed by the analysis of the calculated Fukui and Parr functions reactivity indices. Transition states analysis showed that the experimentally reported product is both kinetically and thermodynamically preferred than the other regioisomeric adduct. The intrinsic reaction coordinates analysis indicated that in contrast to the proposed stepwise mechanism by Wen and co-workers, the reaction proceeds in one step without formation of any stable intermediate. Analysis of the global electron density transfer (GEDT) showed that the corresponding transition state is relatively polar and the electron density is fluxed from 1,3-dimethylindole toward ortho-quinone methide. Because of the polar character of the transition state, the reaction accelerates in ethanol, as a polar solvent, in comparison to the gas phase. Analysis of the frontier molecular orbitals showed that the HOMO orbital of 1,3-dimethylindole as a donor is also the frontier effective-for-reaction molecular orbital (FERMO). According to the Wiberg bond indexes and atoms in molecules analysis, it was found that both reactive channels take place via an asynchronous concerted mechanism.
KeywordsPolycyclic indoline 1,3-Dimethylindole ortho-Quinone methide DFT FERMO Local reactivity
I am thankful to the Research Council and Office of Graduate Studies of the University of Ayatollah Alozma Borujerdi for their financial support.
Compliance with ethical standards
Conflict of interest
The author declares that he has no conflict of interest.
- 1.Fringuelli F, Taticchi A (2002) The Diels-Alder reaction: selected practical methods. Wiley, ChichesterGoogle Scholar
- 10.Dewick PM (2002) Medicinal natural products: a biosynthetic approach2nd edn. Wiley, New YorkGoogle Scholar
- 11.Fattorusso E, Scafati OT (2008) Modern alkaloids. Wiley-VCH, WeinheimGoogle Scholar
- 33.Lee C, Yang W, Parr RG (1988) Phys. Rev. B 37:785–789Google Scholar
- 45.Parr RG, Yang W (1989) Density functional theory of atoms and molecules. Oxford University Press, New YorkGoogle Scholar
- 47.Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson GA, Nakatsuji H, Caricato M, Li X, Hratchian HP, Izmaylov AF, Bloino J, Zheng G, Sonnenberg JL, Hada M, Ehara M, Toyota K, Fukuda R, Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O, Nakai H, Vreven T, Montgomery JA, Peralta Jr JE, Ogliaro F, Bearpark M, Heyd JJ, Brothers E, Kudin KN, Staroverov VN, Kobayashi R, Normand J, Raghavachari K, Rendell A, Burant JC, Iyengar SS, Tomasi J, Cossi M, Rega N, Millam JM, Klene M, Knox JE, Cross JB, Bakken V, Adamo C, Jaramillo J, Gomperts R, Stratmann RE, Yazyev O, Austin AJ, Cammi R, Pomelli C, Ochterski JW, Martin RL, Morokuma K, Zakrzewski VG, Voth GA, Salvador P, Dannenberg JJ, Dapprich S, Daniels AD, Farkas O, Foresman JB, Ortiz JV, Cioslowski J, Fox DJ (2010) Gaussian 09, revision E. Gaussian, Inc, Wallingford, p 01Google Scholar