A significant role of alkaline cations on the Reimer–Tiemann reaction

Abstract

The Reimer–Tiemann (R–T) reaction was investigated by DFT calculations. A model composed of CHCl₃, PhO⁻(Na⁺)H₂O and [NaOH(H₂O)₂]₂ was employed for geometry optimizations. A K⁺-containing model was also investigated. The dichlorocarbene reagent, which has been thought of for a long time, was found to intervene only transiently in the carbenoid form. In this form, the Na⁺ (or K⁺) coordination to CCl₂ enhances its electrophilicity toward C₆H₅O⁻. The counter ion also works to stabilize the precursor phenoxide ion and intermediates of the substituted phenoxides in the hexagonal pyramidal coordination. The Na⁺-containing reaction consists of seven elementary processes, (K⁺, six ones) with extremely high exothermicity and spontaneity.