Diarylmethanes preparation

This procedure is especially suited for preparing variously substituted diarylmethanes.1 6 The l,l-diaryl-2,2,2-trichloro-ethanes may be converted to the corresponding benzophenones via the l,l-diaryl-2,2-dichloroethylenes7 and to 1,1 -diarylacetic acids.8... 

Substituted diarylmethanes have been prepared from formaldehyde and a variety of its derivatives. Sulfuric acid is a common catalyst. The procedure described is based on the general method of Gordon, May, and Lee. Formic acid is preferable to sulfuric acid as a catalyst because it is capable of acting as a solvent as well, thus eliminating troublesome emulsions. Side reactions such as sulfonation are avoided. 

Biaryls and diarylmethanes. These compounds can be prepared from coupling reactions of aryl iodides with organozinc reagents. Notably biphenylnonaflates are obtained from iodophenyl nonaflates at room temperature and they undergo further coupling at 55-60°. 

Scheme 21 Reactivity of 85 in the preparation of diarylmethane products using Suzuki-Miyaura coupling...

Alkylbenzenes are prepared by the Friedel-Crafts reaction in which benzene is reacted with an alkyl halide in the presence of a Lewis acid such as AlCl. Diarylmethanes are formed in this manner from dichloromethane and triarylmethanes from trichloromethane. 

Numerous applications of the NaBHVTFA deoxygenation of diarylmethanols and related benzylic alcohols have been reported, especially those involving diarylmethanols. In addition to the examples shown earlier,2 diarylmethanes 57-64 have been prepared from the corresponding alcohols with NaBHVTFA. The site of reduction is shown as a bold H. 

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. 

A variety of 2-substituted-3-pyridinols can be prepared by well-known methods. For example, diarylmethyl 2-lliryl ketones are prepared in good yield from ethyl fliroate and diarylmethanes using KNH2 or NaNHj in liquid ammonia and are conveniently converted to XII-279. p-Chlorobenzyl 2-furyl ketones, which can be converted to XU-280, can be prepared from p-chlorophenylacetonitrile and ethyl furoate by condensation in the presence of alkoxide followed by hydrolysis and decarboxylation. 2-Pyrryl ketones are also formed in the last step. Several 2-furyl ketones are cleaved under these reaction conditions and do not give 3-pyridinols. ... 

In the case of benzylzinc chlorides prepared from benzylic chlorides by LiCl-promoted insertion of zinc, cross-coupling with aryl and aminoheteroaryl chlorides occurs smoothly in a mixture of THF and NMP with a catalytic system formed from Ni(acac)2 and PPhj (Scheme 4.89) [282]. Illustratively, the diarylmethane 388 is obtained in 90% yield after Ih at 60 °C. Similar reaction conditions are also efficient using aromatic bromides and tosylates as electrophilic partners. 

Specifically, diphenylmethane was prepared in >90% yield by the reaction of either Ph4Sn or Ph3SnMe with BrCH2Ph in the presence of PhCH2Pd(PPh3)2Cl.f The synthesis of polychlorinated diarylmethanes shown in Scheme 26 is noteworthy despite the modest product yields.f Most of the other currently known examples of Pd-catalyzed aryl-benzyl coupling pertain to the synthesis of heteroarenes (Scheme 27). 

Pratt, E. E, and McGovern, T. P, Oxidation by solids. 1. Oxidation of selected alcohols by manganese dioxide, J. Org. Chem., 26, 2973, 1961 Pratt, E. E, and Van de Castle, J. E, Oxidation by solids. 11. The preparation of eithertetraarylethanes or diarylketones by oxidation of diarylmethanes with manganese dioxide,/ Org. Chem.,... 

Other methods of activating organostannanes have been reported in literature. These methods capitalize on the use of fluoride ions and the formation in situ or not of activated hypervalent stannate intermediates. For instance, Garcia Martinez has used the hypervalent tin reagent tetrabutylammonium difluorotribenzylstannate 24 (prepared in quantitative yield from BnsSnF) in the synthesis of unsymmetrical diarylmethanes... 

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