期刊
RSC ADVANCES
卷 5, 期 103, 页码 84797-84809出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c5ra15662a
关键词
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资金
- Ministerio de Economia y Competitividad of the Spanish Government [CTQ2013-45646-P]
- FONDECYT [1140341]
- Millennium Nucleus of Chemical Processes and Catalysis (CPC) [NC120082]
- Ministerio de Economia y Competitividad
- European Social Fund [BES-2014-068258]
- [DI-UNAB-793-15/R]
The high reactivity of carbonyl compounds towards the carbenoid intermediate cis-IN, generated in situ by the addition of methyl isocyanide to dimethyl acetylenedicarboxylate (DMAD), has been investigated at the MPWB1K/6-311G(d,p) computational level by using Molecular Electron-Density Theory (MEDT). This multicomponent (MC) reaction is a domino process that comprises two sequential reactions: (i) the formation of a nucleophilic carbenoid intermediate trans-IN; and (ii) the nucleophilic attack of cis-IN on the carbonyl compound, resulting in the formation of the final 2-iminofuran derivative. The present MEDT study establishes that the high nucleophilic character and the electronic structure of the carbenoid intermediate, cis-IN, together with the specific approach mode of the carbonyl C=O double bond during the nucleophilic attack of the sp(2) hybridised carbenoid C4 center of cis-IN on the carbonyl C5 carbon of acetone, enables the formation of the C4-C5 single bond with a very low activation enthalpy, 3.3 kcal mol(-1), without any external electrophilic activation of the carbonyl group, and the subsequent ring closure through the downhill formation of the C-O single bond. The Bonding Evolution Theory (BET) study for the formation of the 2-iminofuran allows characterisation of the mechanism as a [2n + 2n] cycloaddition, ruling out the proposed 1,3-dipolar cycloaddition mechanism.
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