Vanadium oxytrihalide (VOX3)

Abstract

(A) The intramolecular oxidative biaryl coupling is one of the most significant applications of VOX3 in organic synthesis. Numerous important natural products containing the biaryl segments have been synthesized.1,2 As example, the oxidative cyclization with VOF3 of bursehernin resulted in a new deoxy isosteganone.2 (Figure Presented) (B) VOX3 also promotes the intermolecular oxidative biaryl coupling. Weck et al.6 synthesized the triphenylene grafting functional alkyl chain by oxidative arylaryl coupling of the tetraalkoxy-substituted biphenyls with the bisalkylated catechols using VOF3 in the presence of boron trifluoride diethyl ether. (Figure Presented) (C) Hartenstein et al.9 studied the diastereoselective synthesis of the aporphine alkaloid (+)-cataline and they found that the reaction of (±)-glaucine with VOF3 gave (±)-cataline, respectively. Carefully chromatographic separation of the reaction product yields to small amounts of the respective diastereomeric cis-4-hydroxyaporphine. Its antipode could also be isolated. (Figure Presented) (D) VOX3 can be used as metal oxidant in the regio- and stereoselective dimerization of stilbene derivatives. Velu et al.8 reported that the treatment of 12-hydroxy-3-methoxystilbene with VOF3 gave the tricuspidatol A analogue. (Figure Presented) (E) Filipan-Litvic et al. and Gradillas et al. reported that vanadium oxytrihalide could be also used as metallic oxidant aromatization agent.10 An example of the rapid, efficient, room-temperature aromatization of Hantzsch 1,4-dihydropyridines with vanadium(V) salts is given. (Figure Presented) (F) Villemin et al.11 developed a microwave-assisted, dry reaction (solvent-free) for the one-step synthesis of metallophthalocyanines. The strong near-infrared absorbent vanadyl phthalocyanine complex was obtained from phthalonitrile and VOCl3 as blue-green solid in high yield (81%).(Figure Presented) (G) VOX3 were also used in the synthesis of VO(salen)(X) complexes, which are powerful catalysts for the asymmetric addition of the cyanide nucleophile to benzaldehyde.13 (Figure Presented). © Georg Thieme Verlag Stuttgart.