1202160-56-2Relevant academic research and scientific papers
Photochemical formation and chemistry of long-lived adamantylidene-quinone methides and 2-adamantyl cations
Basaric, Nikola,Zabcic, Ivana,Mlinaric-Majerski, Kata,Wan, Peter
, p. 102 - 116 (2010)
(Chemical Equation Presented) Hydroxymethylphenols strategically substituted with the 2-hydroxy-2-adamantyl moiety, AdPh 8-10, were synthesized, and their photochemical reactivity was investigated. On excitation to the singlet excited state, AdPh 8 undergoes intramolecular proton transfer coupled with a loss of H2O giving quinone methide 8QM. The presence of 8QM has been detected by laser flash photolysis (CH3CN-H2O 1:1, τ = 0.55 s) and UV-vis spectroscopy. Singlet excited states of AdPh 9 and 10 in the presence of H2O dehydrate giving 9QM and 10QM. Photochemically formed QMs are trapped by nucleophiles giving the addition products (e.g., Φ for methanolysis of 8 is 0.55). In addition, the zwitterionic 9QM undergoes an unexpected rearrangement involving transformation of the 2-phenyl-2-adamantyl cation into the 4-phenyl-2-adamantyl cation (Φ ～ 0.03). An analogous rearrangement was observed with methoxy derivatives 9a and 10a. Zwitterionic 9QM was characterized by LFP in 2,2,2-trifluoroethanol (τ = 1 μs). In TFE, in the ground state, AdPh 10 is in equilibrium with 10QM, which allowed for recording the 1H and 13C NMR spectra of the QM. Introduction of the adamantyl substituent into the o-hydroxymethylphenol moiety increased the quantum yield of the associated QM formation by up to 3-fold and significantly prolonged their lifetimes. Furthermore, adamantyl substituent made the study of the alkyl-substituted quinone methides easier by LFP by prolonging their lifetimes and increasing the quantum yields of formation. 2009 American Chemical Society.
