Synthesis of gem-Dihydroperoxides from Ketones and Aldehydes Using Silica Sulfuric Acid as Heterogeneous Reusable Catalyst

Synthesis of Non-symmetrical Dispiro-1,2,4,5-Tetraoxanes and Dispiro-1,2,4-Trioxanes Catalyzed by Silica Sulfuric Acid

A novel protocol for the preparation of non-symmetrical 1,2,4,5-tetraoxanes and 1,2,4-trioxanes, promoted by the heterogeneous silica sulfuric acid (SSA) catalyst, is reported. Different ketones react under mild conditions with gem-dihydroperoxides or peroxysilyl alcohols/β-hydroperoxy alcohols to generate the corresponding endoperoxides in good yields. Our mechanistic proposal, assisted by molecular orbital calculations, at the ωB97XD/def2-TZVPP/PCM(DCM)//B3LYP/6-31G(d) level of theory, enhances the role of SSA in the cyclocondensation step. This novel procedure differs from previously reported methods by using readily available and inexpensive reagents, with recyclable properties, thereby establishing a valid alternative approach for the synthesis of new biologically active endoperoxides.

Synthesis of Primary gem-Dihydroperoxides and Their Peroxycarbenium [3 + 2] Cycloaddition Reactions with Alkenes

It is long known that dihydroperoxidation of aliphatic aldehydes is extremely difficult and normally stops halfway at the hydroxyhydroperoxide stage. This strange phenomenon now has been explored, and a highly effective protocol for conversion of aliphatic aldehydes into gem-dihydroperoxides has been developed. Silyl protection of primary gem-dihydroperoxides, which is also a challenge due to unexpected based-induced decomposition, was achieved using 2,6-lutidine as the base. The silyl-protected gem-dihydroperoxides were then examined in a peroxycarbenium [3 + 2] cycloaddition reaction with alkenes for the first time. Aromatic substrates normally reacted smoothly, affording the expected 1,2-dioxolanes smoothly. Aliphatic aldehydes generally failed to yield 1,2-dioxolane. In all cases, unexpected formation of either a chlorohydrin or a 1,2-dichloride (with Cl atoms derived from TiCl₄) depending on the alkene employed was observed, which displays some so far unknown facets of the cycloaddition and helped to gain many mechanistic insights.

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

The catalyst H_3+x PMo_12-x ⁺⁶ Mo_x ⁺⁵ O₄₀ supported on SiO₂ was developed for peroxidation of 1,3- and 1,5-diketones with hydrogen peroxide with the formation of bridged 1,2,4,5-tetraoxanes and bridged 1,2,4-trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5-tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim-methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.

Heteropoly acid/NaY zeolite as a reusable solid catalyst for highly efficient synthesis of gem-dihydroperoxides and 1,2,4,5-tetraoxanes

gem-Dihydroperoxides and 1,2,4,5-tetraoxanes were synthesised from aldehydes and ketones catalysed by heteropoly acid/NaY zeolite (HPA/NaY) as a new, effective and reusable solid catalyst using 30% aqueous hydrogen peroxide at room temperature. The reactions proceeded with high rates and excellent yields.

Activation of aqueous hydrogen peroxide for non-catalyzed dihydroperoxidation of ketones by azeotropic removal of water

Cyclic and acyclic ketones were selectively converted to gem-dihydroperoxides in 72–99% yield with 30% aq. hydrogen peroxide by azeotropic distillation of water from the reaction mixture without any catalyst.