Phosphomolybdic and phosphotungstic acids as efficient catalysts for the synthesis of bridged 1,2,4,5-tetraoxanes from β-diketones and hydrogen peroxide

Abstract

Phosphomolybdic acid (PMA) and phosphotungstic acid (PTA) efficiently catalyze the addition of H2O2 to β-diketones to form bridged 1,2,4,5-tetraoxanes. These reactions are not accompanied by the formation of monocyclic peroxides containing hydroxy and hydroperoxide groups or polymeric peroxides. The use of these catalysts made it possible to obtain bridged tetraoxanes from easily oxidizable benzoylacetone derivatives and α-unsubstituted β-diketones. The syntheses are scaled up to ten grams. The resulting peroxides can be easily isolated from the reaction mixture by column chromatography. The yield of tetraoxanes depends on the structure of β-diketone and varies from 12 to 83%. NMR monitoring of two bridged 1,2,4,5-tetraoxanes synthesis was carried out.

Catalyst Development for the Synthesis of Ozonides and Tetraoxanes Under Heterogeneous Conditions: Disclosure of an Unprecedented Class of Fungicides for Agricultural Application

“…13 C NMR (75.48 MHz, CDCl 3 ): δ =10.0, 14.2, 22.7, 24.0, 27.8, 29.6, 31.7, 59.3, 111.0 ppm. The physical and spectral data were consistent with those previously reported …”

“…For this reason, the selective synthesis of peroxides on the basis of diketones is a very difficult task. We have found that the selective synthesis of peroxides can be carried out by peroxidation of β‐diketones catalyzed by strong acids (e.g., H 2 SO 4 , HClO 4 , HBF 4 , and BF 3 ⋅ Et 2 O) and heteropolyacids (e.g., phosphomolybdic, phosphotungstic) . Peroxidation of β,δ′‐triketones employing heteropolyacids as a catalyst leads to the formation of bridged keto‐tetraoxanes, bridged keto‐ozonides, and tricyclic monoperoxides .…”

“…7‐Hexyl‐1,4‐dimethyl‐2,3,5,6‐tetraoxabicyclo[2.2.1]heptane (5 g) : Slightly yellow oil. Yield 59 %, 207.7 mg, 0.96 mmol.…”

“…PMA is able, when interacting with H 2 O 2 , to form peroxo complexes with the ‐Mo‐O‐O‐ fragment . However, taking into account that the PMA/H 2 O 2 system oxidizes alkenes, alcohols, and dicarbonyl compounds, the result of the peroxidation of 1,3‐ and 1,5‐diketones under heterogeneous conditions is a priori unpredictable and not obvious. We have chosen SiO 2 as a support for the PMA, because it is one of the most convenient and available materials for various promotions and catalytic systems…”

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

“…The use of these catalysts made it possible to obtain bridged tetraoxanes from easily oxidizable benzoylacetone derivatives and α-unsubstituted β-diketones [429]. …”