Riemer-Tiemann reaction

This is a nifty little way to turn catechol or guaiacol into protocate-chualdehyde or vanillin using what is called the Riemer-Tiemann reaction [137 p824, 138], It is a really ancient reaction and only works on benzene molecules that have an OH group. One needs to use KOH instead of NaOH because it is better at promoting para substitutions (don t ask). And if one is going to make vanillin from guaiacol then there needs to be a little ethanol in the reaction as well. 

Phenols react easily with chloroform in the presence of base in the Riemer-Tiemann reaction. The reaction of chloroform with sodium... 

Photoformylation (the photo-Riemer-Tiemann reaction) of phenols (phenol, 2-methyl, 3-methyl, 4-methyl, 4-chloro, 4-bromo, 4-nitro and 4-phenyl phenol) has also been studied by irradiation in chloroform with KOH and pyridine. The yields reported are variable but formylation is reported only to occur in the 2-position ° °. This process involves the addition to phenol of radicals produced from chloroform. An electron transfer mechanism (transfer from excited state phenol to chloroform) is thought to be involved. The radical ion pair eliminates HCl and combination affords the products 232-234 (Scheme 26). The principal product is the ether and this undergoes partial conversion to the formate. The other products formed in low yield are the aldehydes . In another application of the photo-Riemer-Tiemann reaction, this time in cyclodextrin, the phenols can be converted into 4-hydroxybenzaldehydes with high selectivity . ... 

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