Gross formylation

Friedel-Crafts acylation reactions of aromatics are promoted by Tilv complexes.104 In some cases, a catalytic amount of the titanium compound works well (Scheme 28). In addition to acyl halides or acid anhydrides, aldehydes, ketones, and acetals can serve as electrophile equivalents for this reaction.105 The formylation of aromatic substrates in the presence of TiCl4 is known as the Rieche-Gross formylation metalated aromatics or olefins are also formylated under these conditions.106... 

Therefore we choose the Gross formylation, which is a mild electrophilic reaction easy to be controlled [45]. By playing around catalyst, solvent, temperature and molar... 

Costisella, B., and Gross, H., a-Substituted phosphonates. Part 22. Synthesis and NMR spectra of open-chain and cyclic acetals of formyl phosphonates and formyl diphenylphosphine oxide, J. Prakt. Chem., 319, 8, 1977. 

Gross and co-workers reported an interesting direct aldehyde synthesis using alkyl ortho-formates that is particularly suitable for phenols, as alkylformates are unable to act as formylating agents under Friedel-Crafts conditions. Aldehydes of phenol are obtained in good yields when phenols react with orthoformates in the presence of aluminum chloride (Eq 1.12). 

Gross and Mirsch found that reaction of aromatics with dichloro methyl methyl sulfide and aluminum chloride yield aromatic aldehydes. However, the yields were lower compared to using dichloromethyl ethers as formylating agent. Cumene aldehyde was obtained in a 41%, mesityl aldehyde in 49% and 2-naphthyl aldehyde in 52% yield (Eq 1.16). 

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