245118-72-3Relevant academic research and scientific papers
Spectroscopic characterization, reactivity, and reactions of (arene)Cr(CO)3-stabilized γ-propargyl-allenyl cations
Müller, Thomas J. J.,Ansorge, Markus,Polborn, Kurt
, p. 3690 - 3701 (2008/10/08)
(Arene)Cr(CO)3-stabilized γ-propargyl-allenyl cations Cr(CO)3(η6-R1C6H 4)C≡CC+R2R3 (2) are reactive intermediates in the synthesis of arene-complex-substituted allenes or propargyl derivatives using mild in situ ionizations of the corresponding propargyl derivatives Cr-(CO)3(η6-R1C6H 4)C≡CCXR2R3 (X = OH, OAc). The regioselectivity of the nucleophilic attack is strongly dependent on the substitution pattern on the propargyl side chain, i.e., steric and electronic factors. In a representative case of a stable cation (2a; R1 = H, R2 = R3 = Ph) the structure investigation of this ambident electrophile by NMR spectroscopy and UV/vis spectroscopy reveals that a considerable contribution of the allenylium resonance structure accounts for a strong participation of the chromium carbonyl fragment in the efficient stabilization. The reactivity of 2a was studied by measuring the UV/vis kinetics for the nucleophilic trapping reactions revealing that the complexed cation 2a is by 2 orders of magnitude less reactive than the corresponding free ligand.
