Diarylmethane derivatives benzylation

Trimethylaluminum exhaustively methylates O-functions and thus converts tert. alcohols to alkanes, ketones to gem-dimethyl compounds, and carboxylic acids to terUhuiyX derivatives . AgC104-SnCl4 gives high yields of diarylmethanes by benzylation of arenes, e. g. with benzyl alcohol . 

Encouraged by these results, the reaction of benzylic alkoxides with dichloroborane was examined. These reactions provide an alternative route to diarylmethane derivatives (Schane 23.77). The deoxygenation of alkoxides using dichloroborane provides useful evidence for understanding the importance of Lewis acidity in previously reported deoxygenation methods operating through alkoxide intermediates. ... 

The intermolecular Friedel-Crafts alkylation with benzyUc and aUyUc halides occurs at room temperature in CH2CI2. Diarylmethanes are also obtained in moderate yields from arenes and benzyl alcohols on heating the mixtures with InCls 4H2O and acetylacetone at 120°. l-VinyltetraUn and 4-vinyltetrahydrDisoquinoline derivatives are readily formed by an intramolecular aUylation. ... 

Unsymmetrical biaryh and diarylmethanes. Negishi et al have used a nickel-(0) complex or a palladium(0) complex as catalyst for the cross-coupling of aryl-or benzylzinc halides with aryl halides at room temperature to form biaryls or diarylmethanes. The zinc derivatives are prepared by reaction of aryl- or benzyl-lithium with zinc chloride or bromide. 

This reaction was initially studied by von Baeyer in 1872. It is an acid-catalyzed condensation of aromatic compounds with formaldehyde or formaldehyde derivatives. In normal conditions, the reactive benzene derivatives such as phenols and arylamines are applied to condense with formaldehyde however, a small number of less-reactive aromatics have also been used in this reaction, including benzene, toluene, benzyl chloride,biphenyl, iodobenzene, naphthalene, and mesitylene. Although no yields were given in the early studies, it is reasonable to obtain 70-80% yield for this type of reaction. Many other reactions have been developed to synthesize diarylmethanes, including Katritzky s benzotriazole method, Kochi s dealkylative coupling," Fukuzaw s 1,3-propandiol method, and the reduction method. In general, the condensation occurs at the /tflra-position of substituted aromatics. 

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