Copper-catalyzed Transformations Of Functional Groups From Arylboronic Acids In Water

Aromatic compounds are widely used as chemicals, synthetic intermediates,pharmaceuticals, natural products and materials. Their properties are highly dependedon the functional groups on aromatic rings. Therefore, the functional grouptransformation is an important direction in organic chemistry. In this dissertation, somefunctional group transformations from arylboronic acids and the correspondingmechanism were investigated, and some important results were obtained as follows:A simple and general method has been developed for transformations of variousfunctional groups (-I,-N₃,-SO₂R,-OH,-NH₂and-NO₂) on aromatic rings fromarylboronic acids in water under air. The protocol uses cheap and readily availableinorganic salts (KI, NaN₃, NaSO₂R, NaOH, and NaNO₂) and aqueous ammonia as thefunctional group sources. The present method shows the following advantages:(1) mildcondition, environmentally friendly water as the solvent;(2) excellent tolerance towardsvarious functional groups in the substrates;(3) it is suitable for the substrates containingthe donating and withdrawing groups;(4) easy workup (most of products were isolatedby extracting with ethyl acetate from aqueous solution;(5) the catalyst system in watercould be recovered and reused. This method will attract much attention in academic andindustrial fields.The mechanism for transformations of various functional groups on aromatic ringsfrom arylboronic acids has been developed. The NMR, ESR and other experimentsprovided the following evidences:(1) the oxygen-involving functional grouptransformation could be performed in low yield in the absence of copper catalyst;(2)coordination of oxygen with copper and boron was observed by NMR and ESR;(3)Cu(I), Cu(II) and Cu(III) were determined, and the result showed that the catalytic cycleunderwent transform of the three copper salts. Therefore, the functional grouptransformation could undergo the intermediate from coordination of oxygen with copperand boron, and formation of the intermediate led to weak C-B bond which was helpfulfor nucleophilic attack of nucleophilic reagent to carbon of C-B bond. This mechanismcan provide a base for copper–catalyzed coupling reactions from arylboronic acids.Some reactions were predicted and performed well according to this mechanism.