Regioselective Conversion of Arylboronic Acids to Phenols and Subsequent Coupling to Symmetrical Diaryl Ethers

Regioselective Synthesis of Phenols and Halophenols from Arylboronic Acids Using Solid Poly(N‐vinylpyrrolidone)/ Hydrogen Peroxide and Poly(4‐vinylpyridine)/Hydrogen Peroxide Complexes

“…[9] We have already reported the ipso-halogenation, [10] ipso-nitration [11] and ipso-hydroxylation [12] of arylboronic acids. An efficient ipso-nitration procedure for arylboronoc acids under mild condition has been reported recently.…”

“…[12] This method needs several hours for completion of the reaction and further work-up and purification is needed. Other methods known for this transformation also have similar limitations.…”

Diastereomeric Resolution of a Racemic Biarylboronic Acid and Its Application to Divergent Asymmetric Total Syntheses of Some Axially Chiral Natural Products

“…[7] Since ab oronic acid functional group is readily converted into either ah ydrogena tom [8] or ah ydroxy group, [9] an axially chiral biarylboronic acid generated via the diastereomeric resolution using ab oronic acid as the resolving group [7] could be utilized as ac ommon intermediate in the total syntheses of various axially chiral biaryl natural products.H erein, we present the diastereomeric resolution of racemic biarylboronic acids using ab oronic acid as the resolving group to provide an axially chiral biarylboronic acid. Using the resulting axially chiral biarylboronic acid as ac ommon intermediate, the asymmetric total syntheses of deshydroxytetramethylcupressuflavone (1) [10] and desmethylkotanin (2) [11] andt he formal synthesiso fh ibarimicinone (3) [6a, 12,13] were demonstrated.…”

“…Aqueous basic hydrolysis of 11' ' providedt he enantiomer( S)-5, [16] which was subjectedt oo xidation with hydrogen peroxide in NaOH solution [9] without furtherp urification, and subsequent protection of the resulting hydroxy group with CH 3 Ip rovided compound 14 in 95% yield over three steps.O nce again, chiral MIDA 10 used for the resolution could be recovered in quantitativey ield by the same procedure as used in the conversion of compound 11 into 6 via protodeboronation. [20] Ther esulting compound 14 was further transformed to the ester 15 without any loss of enantiopurity via metal-halogen exchangew ith n-BuLi ands ubsequent trappingo ft he resulting organolithium compound with methyl chloroformate.…”

Photocatalytic hydroxylation of arylboronic acids using continuous flow reactors

“…[3][4][5][6] Although direct boronic acid hydroxylation has received attention, it oen requires the use of strong oxidising agents or toxic metal catalysts. 3,[7][8][9][10][11][12][13][14] Recently, a number of alternative methods have been described, based on the generation of superoxide free radical species (O 2 c À ). 15,16 In this context, photocatalysis has emerged as a promising methodology [17][18][19] which is compatible with a variety of substrates and catalysts, including metal-free dyes.…”