Oxidative coupling of phenols using vanadium tetrachloride and vanadium oxytrichloride

Preparation and catalytic applications of partially fluorinated binaphthol ligands

“…Since only one of the naphthyl moieties in 3 is fluorinated, we opted to try the oxidative coupling between 16 and 2-naphthol. Oxidative coupling of 2-naphthols can be promoted by several metal catalysts such as complexes of ruthenium [16], titanium [17], vanadium [18], manganese [19], copper [20], and iron [21]. Unfortunately, the widely used FeCl 3 -catalyzed reaction cannot be used in our case because the fluorinated 2-naphthol 16 reacts with FeCl 3 to give chlorinated product 17 (Scheme 4) [9].…”

Brown algal polyphenols: synthesis of "fucophlorethol A" octamethyl ether (2,2′,4,6,6′-pentamethoxy-4′-(2,4,6-trimethoxyphenoxy)biphenyl)

“…VC14 (6.5 mL, 62 mmol; Alfa/Ventron) was added with stirring during 5 min. and the reaction mixture was stirred under N2 at -25'C for I h.' Then 2 N aqueous H'SO, (100 mL) was added, and the mixture was stirred vigorously under N-, for I0 min (19). Partitioning between the acidic aqueous phase and CHCI, (75 mL) gave a yellow-brown organic layer, …”

“…The commercial availability of bromo-2,4,6-trimethoxybenzene (4) made it appealing to~approach the problem as an Ullmann ether synthesis On the other hand, reports of VCI,-or VOC1,-catalyzed dehydrodimerization predominantly in the paru position of unprotected phenols (18,19), including the production in one instance of 2,2'-dihydroxybinaphthyl (19), suggested that 2 might be directly synthesized by treating the conimercially available 3,5-dimethoxyphenol (1) with VCI, or VOC13. The three-step synthesis o f 6 reported herein should serve as a pattern for eventual synthetic approaches to the "tetrameric" fucodiphlorethol A and the higher homologues.…”

CuBr/H2O2-Mediated Oxidative Coupling ofN,N-Dialkylarylamines in ­Water: A Practical Synthesis of Benzidine Derivatives

“…5 A number of methods for the coupling reaction have been reported. [6][7][8][9][10][11] Among them, oxidative coupling of aniline derivatives provided an efficient access to benzidine derivatives. Recently, TiCl 4 10 and 1,8-bis(diphenylmethylium)naphthalenediyl dications 11 were both reported to be effective oxidants for such coupling reactions, although the large excess of anilines (in the former) and the relatively hard-to-obtain dications (in the latter) retarded their acceptance as practical approaches.…”