Pd-catalyzed Cross-Coupling Of 1,1-Diborylalkanes With Aryl Triflates

Organic boron compounds are important organic compounds, which play an important role in the Suzuki-Miyaura cross-coupling reaction. In the last few decades, the Suzuki-Miyaura cross-coupling reactions catalyzed by transition metals such as Pd, Cu, Ni and so on have achieved great results. But the development and application of new type of organic boron reagent is still a great challenge.In recent years,1,1-diborylalkanes reagents as a new development of the nucleophile has attracted more and more attentions. In addition, the aryl OTf which is closely related to the activity of aryl halogen also plays an important role in the process of organic synthesis. This paper reported the palladium catalyzed cross-coupling reaction between aryl OTf electrophilic reagents and 1,1-diborylalkanes. The reaction applies not only to the special diborylmethane, but also to the substituent 1,1-diborylalkanes. The catalyst system is as follows:cheap and readily available acetate palladium asthe catalyst, cheap triphenyl phosphine as the ligands,1M tetrabutylammonium hydroxide as the base,1,4-dioxane as the solvent. This strategy reaches very good effect. In addition, the reaction has good functional group compatibility and can be compatible with ether, trifluoromethyl, trifluoro methoxy, cydopentyl, formyl, naphthyl,aldehyde, 4-chloro-3-methyl and 3,5-dimethyl etc.1,1-diborylalkanes can be compatible with substituted groups such as ethyl, diborylnaphthylethyl, propyl, butyl. In addition,due to many aryl-OTf came from the natural substances phenol. So this method showed the advantage of aryl triflates in cross-coupling reaction than aryl halogen in some occasions, especially in the modification of natural products containing phenolic hydroxyl groups. Certainly, competitive reactions can also show a lower activity of aryl OTf than aryl halide (bromine, iodine).Besides, we also study the inert aryl electrophilic reagents of aryl C-0 bond with 1,1-diborylalkanes, but did not get any reaction products. Whether we used the highly activite diborylmethane or the ordinary 1,1-diborylalkanes, the reaction could n’t take place. Secondly, we tried copper catalyst system and nickel catalyst system, butfound that it had not obtained the corresponding target product, so on inert aryl C-0 bond electrophilic reagents and 1,1-diborylalkanes still need further exploration.