Bis(pentafluorophenyl)borinic Acid as a Highly Effective Oppenauer Oxidation Catalyst for Allylic and Benzylic Alcohols

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

“…Apparently, the stronger Lewis acidity of perfluorinated diarylborinic acid compared to analogous pentafluorophenylboronic is the most important factor responsible for the catalytic activity of the former compounds. 154 A water-soluble [Ir(COD)Cl] 2 catalyst (COD: cycloctadiene) in combination with 2,2′-biquinoline-4,4′-dicarboxylate has been found highly efficient for the selective Oppenauer oxidation of secondary benzylic and aliphatic alcohols to the corresponding ketones at a catalyst/substrate ratios ranging between 0.4 and 2.5%. 155 Methyl trioxorhenium has been found a robust catalyst to effect epoxidations and alcohol oxidations using hydrogen peroxide as oxidizing reagents.…”

Arylboron Compounds as Acid Catalysts in Organic Synthetic Transformations

“…We have found bis(pentafluorophenyl)borinic acid (2) to be a suitable OPP catalyst for primary and secondary allylic and benzylic alcohols. [11] Borinic acid 2 is prepared from the known chloroborane Scheme 13 (C 6 F 5 ) 2 BCl by hydrolysis with 2  aqueous HCl. [12] It is obtained as a white, microcrystalline solid, which can be readily handled in air, and is soluble in many organic solThe addition of magnesium sulfate efficiently prevents the inactivation of 2 and hence promotes the oxidation.…”

Organoboronic Acids and Organoborinic Acids as Brønsted–Lewis Acid Catalysts in Organic Synthesis

“…α-Bromoacrolein is a useful dienophile in the Diels-Alder process because of the exceptional synthetic versatility of its resulting adducts: e.g., an important intermediate for prostaglandin synthesis [19a]. In the presence of 10 mol% of 3a, α-bromoacrolein and cyclopentadiene in dichloromethane undergo a smooth Diels-Alder reaction to give the (S)-bromoaldehyde cycloadduct in quantitative yield, 95% ee and 94:6 (exo:endo CHO) diastereoselectivity Hawkins et al have reported a simple, efficient catalyst for the Diels-Alder reaction based on a chiral alkyldichloroborane (4,Equation 21) [21]. A molecular complex between methyl crotonate and the chiral catalyst has been isolated for the first time.…”

“…For the selective oxidation of allylic alcohols in the presence of saturated alcohols, activated MnO 2 is still one of the most useful reagents, despite the large amount required. Ishihara and Yamamoto et al have found that (C 6 F 5 ) 2 BOH is a suitable OPP catalyst for primary and secondary allylic and benzylic alcohols [4]. (C 6 F 5 ) 2 BOH is prepared from (C 6 F 5 ) 2 BCl with aqueous 2 M HCl [5].…”

“…In oxidations of equimolar mixtures of 10 Organoboronic Acids and Organoborinic Acids as Brønsted-Lewis Acid Catalysts in Organic Synthesis OH CHO cat. Ar n B(OH) 3-n (2 mol%), t-BuCHO (6 equiv) benzene, 80 °C, 3 h C 6 F 5 B(OH) 2 : (0%); (C 6 F 5 ) 2 BOH: (>99%); (C 6 F 5 ) 3 B: (>99%) (4) geraniol and β-citronellol, geranial is obtained in 96% yield and most of the β-citronellol is recovered unchanged.…”