Benzylic Oxidation Catalyzed by Dirhodium(II,III) Caprolactamate

Abstract

[reaction: see text] Dirhodium caprolactamate [Rh2(cap)4] is an effective catalyst for benzylic oxidation with tert-butyl hydroperoxide (TBHP) under mild conditions. Sodium bicarbonate is the optimal base additive for substrate conversion. Benzylic carbonyl compounds are readily obtained, and a formal synthesis of palmarumycin CP2 using this methodology is described.

Stereoselective Synthesis of 4‐Dehydroxydiversonol Employing Enantioselective Palladium‐Catalysed Domino Reactions

“…Several procedures failed in the benzylic oxidation, however, by treatment of 25 with excess tert-butylhydroperoxide in the presence of catalytic amounts of dirhodium-tetrakiscaprolactamate (26) and NaHCO 3 , the desired chromanone 6 could finally be obtained in 63 % yield. [19] Furthermore, an alternative procedure employing [MnA C H T U N G T R E N N U N G (OAc) 3 ] as catalyst led to 6 in even 71 % yield. [20] Intramolecular acylation at the a position of the keto functionality by the ester moiety in 6 in the presence of TiCl 4 and NEt 3 gave the tetrahydroxanthenone 5 in 63 % yield.…”

Mechanistic study on benzylic oxidations catalyzed by bismuth(III) salts: X-ray structures of two bismuth–picolinate complexes

“…1 Traditionally, these reactions involve the use of stoichiometric quantities of potent oxidants such as potassium permanganate or potassium dichromate. 2 In the last decade, chemists have been developing alternative processes using Co, 3 Cr, 4 Mn, 5 Rh, 6 Ru, 7 Zn 8 and Fe 9 species among others. 10 With increasing environmental concerns, focus on non-toxic, benign catalysts has assumed greater importance.…”

Monodispersed poly(4-vinylpyridine) spheres supported Fe(III) material: An efficient and reusable catalyst for benzylic oxidation

“…In the past decade, tremendous efforts have been devoted to homogeneous catalysts for benzylic oxidation [13][14]. For example, transition metal salts and complexes containing Cr(CO) 6 [15], CoCl 2 [16], Co(OAc) 2 ·4H 2 O [17], Mn(salen) [18][19], RuCl 3 [20][21], RuCl 2 (PPh 3 ) 3 [22], Rh 2 (cap) 4 [23] or Cp 2 VCl 2 [24] have been shown to be good homogeneous catalysts for benzylic oxidation. However, the development of catalysts that are clean, inexpensive, efficient and selective and which reach the standards of green chemistry remains a challenging goal.…”