The Rearrangement of Peroxides for the Construction of Fluorophoric 1,4-Benzoxazin-3-one Derivatives

Gold(I)-catalyzed tandem cyclization/peroxidation of 2-alkynyl-1-carbonylbenzenes with TBHP

A gold(I)-catalyzed tandem cyclization/peroxidation of 2-alkynyl-1-carbonylbenzenes with tert-butyl hydroperoxide (TBHP) has been successfully developed to access 1-peroxidized 1H-isochromene derivatives in moderate to good yields. The use of one of the resultant 1-peroxidized 1H-isochromenes (3a) for the construction of phenyl(8-phenylbicyclo[4.2.0]octa-1(6),2,4,7-tetraen-7-yl)methanone (4), phenyl(3-phenyl-1,3-dihydroisobenzofuran-1-yl)methanone (5) and 2-(2-benzoylphenyl)-1-phenylethan-1-one (6) has also been investigated, respectively.

Catalyst-free coupling of peroxypyrroloindolenines with amines to afford stable peroxyindolenines

Here we report a highly efficient method for coupling of peroxypyrroloindolenines with amines under catalyst-free conditions to obtain stable C2-N peroxyindolenines in high yields with remarkable functional group tolerance. Initial studies have shown that compound 13 exhibits potent inhibition of the B16/F10 cell line with an IC50 value of 2.18 μM.

FeCl2-Mediated Rearrangement of Aminoperoxides into Functionalized Tetrahydrofurans: Dynamic Non-innocence of O-Ligands at an Fe Center Coordinates a Radical Cascade

The selective reaction of cyclic aminoperoxides with FeCl2 proceeds through a sequence of O-O and C-C bond cleavages, followed by intramolecular cyclization, yielding functionalized tetrahydrofurans in 44-82% yields. Replacing the peroxyacetal group in the peroxide structure with a peroxyaminal fragment fundamentally alters the reaction pathway. Instead of producing linear functionalized ketones, this modification leads to the formation of hard-to-access substituted tetrahydrofurans. Although the aminoperoxide cores undergo multiple bond scissions, this cascade is atom-economical. Computational analysis shows that the O-ligands at the Fe center have enough radical character to promote C-C bond fragmentation and subsequent cyclization. The stereoelectronic flexibility of oxygen, combined with iron's capacity to stabilize multiple reactive intermediates during the multistep cascade, explains the efficiency of this new atom-economic peroxide rearrangement.

Catalyst-Assisted Selective Vinylation and Methylallylation of a Quaternary Carbon Center Using tert-Butyl Acetate

The In(OTf)₃-catalyzed α-vinylation of various hydroxy-functionalized quaternary carbon centers using in situ generated isobutylene from tert-butyl acetate is presented as a novel synthetic methodology. Moreover, tert-butyl acetate is a nonflammable feed stock and is a readily available source for the in situ production of vinyl substituents, as demonstrated by the vinylation reaction with quaternary hydroxy/methoxy compounds. Moreover, an excellent selectivity for methylallylation over vinylation was obtained with Ni(OTf)₂ as a catalyst. In the case of peroxyoxindole, methylallyl-functionalized 1,4-benzoxazin-3-one derivatives were formed through the sequential rearrangement of peroxyoxindole followed by the nucleophilic attack by isobutylene. The detailed mechanism for this reaction and rationalization for the selectivity are provided using kinetics and density functional theory studies.

One-pot synthesis of 3-trifluoromethylbenzo[b][1,4]oxazines from CF3-imidoyl sulfoxonium ylides with 2-bromophenols

A one-pot two-step fashion for the synthesis of 3-trifluoromethyl-1,4-benzoxazines from CF3-imidoyl sulfoxonium ylides and 2-bromophenols via lithium-bromide-promoted O–H insertion of sulfoxonium ylides and annulation has been demonstrated.

Sequential Oxidative Fragmentation and Skeletal Rearrangement of Peroxides for the Synthesis of Quinazolinone Derivatives

For the first time, the sequential reaction of peroxyoxindole that involves base-promoted oxidative fragmentation to isocyanate formation and primary amine or amino alcohol accelerated skeletal rearrangement to synthesize exo-olefinic-substituted quinazolinone or oxazoloquinazolinone is reported. The advantages of this new reaction include a broad substrate scope and transition-metal-free and room-temperature conditions. The formation of the isocyanate as a key intermediate that accelerates oxidative skeletal rearrangement has been confirmed by trapping experiments and spectroscopic evidence.

Diverse Functionalization of Tetrahydro-β-carbolines or Tetrahydro-γ-carbolines via Oxidative Coupling Rearrangement

We report herein diverse functionalization of tetrahydro-β-carbolines (THβCs) or tetrahydro-γ-carbolines (THγCs) via oxidative coupling rearrangement. The treatment of THβCs or THγCs with t-BuOOH (TBHP) afforded 3-peroxyindolenines, followed by HCl catalyzed indolation to form unexpected 2-indolyl-3-peroxyindolenines. Further rearrangement of these peroxides allows for rapid access to a skeletally diverse chemical library in good to excellent yields.

Application of BF3·Et2O in the synthesis of cyclic organic peroxides (microreview)

A summary of recent applications of Lewis acid BF3·Et2O as a catalyst in the synthesis of cyclic organic peroxides is presented.

Construction of Benzothiophene or Benzothiopheno[2,3-e]azepinedione Derivatives via Three-Component Domino or One-Pot Sequences

An efficient three-component domino or one-pot strategy has been developed for the synthesis of medicinally important benzothiophene and benzothiopheno[2,3-e]azepinedione derivatives for the first time. Amine-promoted selective cleavage of C-S bond of thioisatin is the key step in this process. The reported methodology benefits from environmentally friendly solvent (H₂O), wide substrate scope, good functional group tolerance, and high reaction yields.

Peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones

The sp³-C-H peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones was achieved under mild and simple catalyst-free reaction conditions. A range of biologically important alkylated benzoxazinone peroxides are synthesized in high yield with a good functional group tolerance. The C(sp³)-OO bond was constructed efficiently and could be further converted into C(sp³)-C(sp³), C(sp³)-C(sp²), C(sp³)-C(sp), C-P and C[double bond, length as m-dash]O bonds by late-stage functional group transformations.

Peroxidation of 2-oxindole and barbituric acid derivatives under batch and continuous flow using an eco-friendly ethyl acetate solvent

We have demonstrated the magnetically retrievable Fe(OH)₃Fe₃O₄catalyzed C–H peroxidation of 2-oxindole and barbituric acid derivatives under batch and continuous flow process for the first time.