Rh₂(esp)₂-catalyzed allylic and benzylic oxidations

Abstract

The dirhodium(II) catalyst Rh2(esp)2 allows direct solvent-free allylic and benzylic oxidations by T-HYDRO with a remarkably low catalyst loading. This method is operationally simple and scalable at ambient temperature without the use of any additives. The high catalyst stability in these reactions may be attributed to a dirhodium(II,II) catalyst resting state, which is less prone to decomposition.

MnO2/TBHP: A Versatile and User‐­Friend­ly Combination of Reagents for the Oxidation of Allylic and Benzylic Methylene Functional Groups

“…β ‐Ionone Oxidation: The oxidation of β‐ionone ( 16 ; 20 g, 104 mmol) according to the general procedure gave unreacted β‐ionone (0.55 g, 3 %), 3‐keto‐α‐ionone ( 17 ; 8.5 g, 40 %), and β‐epoxy‐ionone ( 18 ; 4.1 g, 19 %). The 1 H and 13 C NMR spectra of 4‐keto‐α‐ionone ( 17 ) were fully consistent with those reported previously,8a whereas β‐epoxy‐ionone ( 18 ) was identified by GC analysis using synthetic 18 23 as a reference standard.…”

“…Oxidation of Isochroman: The oxidation of isochroman ( 29 ; 10 g, 74.6 mmol) according to the general procedure gave 1‐oxo‐isochroman ( 30 ; 5.0 g, 45 %) and 1‐( tert ‐butylperoxy)isochroman ( 31 ; 8.1 g, 49 %), whose 1 H and 13 C NMR spectra were fully consistent with those reported previously 8a,18…”

Synthesis of Structurally Diversified Benzo[c]chromene Derivatives under (An)aerobic Conditions Catalyzed by CuI

“…And then, the carboxyl negative ion in 6 attacks the carbonyl followed by dehydration to give product 3 . Under aerobic conditions, the methylene on 4‐position is oxidized into two C─O─H bonds ( 8 , the similar allylic oxidations were realized by metal catalyst of Rh 2 (esp) 2 ), and 8 loses a molecule of water to afford product 4 . When there is a hydrogen atom on 3‐position, the partial oxidation takes place first to lead intermediate product 9 .…”

Catalytic Oxidation Processes for the Upgrading of Terpenes: State-of-the-Art and Future Trends

“…After optimization on isophorone, the process was successfully extended to some Recently, the chelating Du Bois' catalyst Rh 2 (esp) 2 (esp= α,α,α ,α -tetramethyl-1,3-benzene dipropionate), possessing a higher oxidation potential (E 1/2 = 1130 mV [56]) proved to efficiently catalyze the solvent-free allylic oxidation of some targeted olefins, using large excess of T-HYDRO (5 equiv. ), at ambient temperature (Table 15) [57]. First, the Rh 2 (esp) 2 catalyst was more efficient than Rh 2 (cap) 4 complex for oxidation of isophorone 43, a structural model of terpenic derivatives, with a 91% conversion in 24 h. Moreover, the catalyst was easily separated by chromatographic purification and reused.…”

“…Allylic oxidation of olefins by Rh 2 (esp) 2 /T-HYDRO under optimized reaction conditions a (adapted from reference[57]). …”