Dilauroyl Peroxide Research Articles

Synthesis of (2-alkylthiothiazolin-5-yl)methyl dodecanoates via tandem radical reaction

A series of (2-alkylthiothiazolin-5-yl)methyl dodecanoates was synthesized from various alkyl N-allylcarbamodithioates and dilauroyl peroxide via a tandem radical hydrogen-abstraction-cyclization-substitution/combination reaction with a 5-exo-trig radical cyclization as a key step. The current route is the first, convenient, and efficient synthesis of (2-alkylthiothiazolin-5-yl)methanol derivatives.

One-pot synthesis of symmetric 1,7-dicarbonyl compounds via a tandem radical addition–elimination–addition reaction

A novel approach to synthesize symmetric 1,7-dicarbonyl compounds via a tandem radical addition–elimination–addition reaction of S-carbonylmethyl xanthates with allylmethylsulfone and its analogues has been developed. Radicals were produced from S-carbonylmethyl xanthates by adding dilauroyl peroxide and reacted with allylmethylsulfone or analogues to generate terminal olefins as intermediates. The excessive radicals reacted with the intermediate olefins immediately to give adducts of symmetric 1,7-dicarbonyl compounds. This is an efficient method to synthesize 1,7-dicarbonyl compounds under mild conditions.

Metal‐Free, Radical Addition to Alkenes via Desulfitative Chlorine Atom Transfer

AbstractAn efficient method for radical additions to unactivated alkenes via desulfitative chlorine‐atom transfer is described. The reaction is based on the use of readily available sulfonyl chlorides as starting materials and cheap radical initiators such as azobisisobutyronitrile (AIBN), di‐tert‐butyldiazene (DTBD), and dilauroyl peroxide (DLP). No transition metal catalyst is required and the reaction takes place under mild conditions at temperatures ≤85 °C.

Design and synthesis of novel benzopyrazolodiazepinones via intra-molecular alkylation of α-alkylcarbonyl radicals mediated by dilauroylperoxide

Using a tin-free strategy, novel 4 H-benzo[ f]pyrazolo[1,5- a][1,3]diazepin-5(6 H)-ones were synthesized in acceptable yields via intra-molecular alkylation over a benzene ring, of α-alkylcarbonyl radicals generated from ethyl pyrazolylbenzylaminoxanthates, using dilauroyl peroxide (DLP) as the radical initiator.

Convenient access to isoindolinones via carbamoyl radical cyclization. Synthesis of cichorine and 4-hydroxyisoindolin-1-one natural products

An efficient and convenient access to 2- tert-butylisoindolin-1-ones via an oxidative radical cyclization process from stable carbamoylxanthates, derived from secondary tert-butylamines, is described. The proposed mechanism for this transformation involves, the generation of a carbamoyl radical, its cyclization to the aromatic system, and the dilauroyl peroxide (DLP) mediated rearomatization to generate the isoindolinone ring system. Additionally, the syntheses of cichorine and 4-hydroxyisoindolin-1-one natural products were carried out to underscore the synthetic potential of this xanthate-based carbamoyl radical-oxidative cyclization.

ChemInform Abstract: New Xanthate‐Based Radical Cyclization onto Alkynes.

AbstractTo bypass the failure of radical cyclization involving a xanthate transfer on alkynes, a new reductive cyclization strategy is completed with the use of a stoichiometric amount of dilauroyl peroxide in iPrOH.

New xanthate-based radical cyclization onto alkynes

To bypass the failure of radical cyclization involving a xanthate transfer on alkynes, a new reductive cyclization strategy has been completed with the use of a stoichiometric amount of dilauroyl peroxide in isopropanol. When the starting xanthates are prepared via a Ugi 4-component reaction with propargylamine, exomethylene lactams are formed in good yields.

Synthesis of spiroindolenine derivatives by a tandem radical-oxidation process

In the present work, a novel stereoselective radical cyclization/oxidation/spirocyclization cascade process using a mixture of n-Bu 3SnH/ dilauroyl peroxide is described. The proposed mechanism for this later process combines a 6- endo cyclization of an aryl radical onto an enamide double bond, and a consecutive oxidative-ionic spirocyclization at C-3 of an indole nucleus. All processes led to the construction of new spiroindolenine derivatives in a one-step synthesis starting from relatively simple starting materials. The organic peroxide appears to act as the initiator and the oxidant.

Radical Conjugated Addition: Addition of Dialkyl Phosphonodifluoromethyl Radical onto Unsaturated Ketones

The free radical addition of phosphonodifluoromethyl radical is reported from iodophosphonate and sodium dithionite, triethylborane, or dilauroyl peroxide as initiator. Triethylborane promoted the radical conjugated addition onto enones.

Synthesis of azepino[4,5-b]indolones via an intermolecular radical oxidative substitution of N-Boc tryptamine

A two-step protocol for the synthesis of azepino[4,5-b]indolone derivatives featuring a xanthate radical oxidative aromatic substitution on the N-Boc protected tryptamine, using dilauroyl peroxide (DLP) as initiator and oxidant, is described.

Ugi/xanthate cyclizations as a radical route to lactam scaffolds

The combination of Ugi reaction and xanthate radical cyclization onto alkenes allows an easy access to various highly functionalized heterocycles. The addition of chloroacetic acid to primary amines, aldehydes and isocyanides in methanol followed by the treatment with potassium ethyl xanthate, affords the xanthate Ugi adducts in good yields. These adducts were then submitted to radical cyclization conditions with dilauroyl peroxide as initiator. The choice of an alkene function properly located on the amine or the aldehyde permits the formation of 5- to 8-membered rings in moderate to good yields.

Synthesis of 3-Arylpiperidines by a Radical 1,4-Aryl Migration

[reaction: see text] A route to 3-arylpiperidines, 3-arylpyridines, and 5-arylpiperidin-2-ones involving a radical 1,4-aryl migration has been explored. The sequence requires a xanthate addition to an N-allylarylsulfonamide, followed by acetylation and treatment with dilauroyl peroxide to give the 1,4-aryl transfer product, which upon acidic hydrolysis affords the desired piperidine derivative.

Carbon—Carbon Bond Formation by Radical Addition—Fragmentation Reactions of O‐Alkylated Enols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Evaluation of the validity of the UN SADT H.4 test for solid organic peroxides and self-reactive substances

Many self-accelerating decomposition temperatures (SADTs) of solid organic peroxides and self-reactive substances have been determined with the UN test method H.4, which is a scaled down test in a small Dewar vessel. For solid organic peroxides and solid self-reactive substances Fierz has questioned this procedure in a recent paper. Fierz concluded that the Dewar test results should not be extrapolated to beyond 8 l packages, owing to the thermal insulation value of solids. On the other hand, long term experience with the test, with a great variety of solid organic peroxides and self-reactive substances show about equal critical temperatures in the small Dewar vessel and on 50 kg scale. In the present work, we first checked, by numerical simulations, the Dewar scale versus the larger scale, in a way comparable with Fierz’ method: both scales are simulated by spheres, consisting of a number of annular layers, for the large scale the usual external heat loss term is used but for the small scale the outside heat transfer is strongly limited. The outcome of these simulations, covering a variety of physical parameters, supports the concerns expressed by Fierz. After this, we performed accurate cooling and heating experiments with solid organic peroxide in the usual Dewar vessel, provided with a large set of thermocouples. The results of these experiments showed that the simulation model for the Dewar vessel has to be changed from a spherical analogue to a short cylinder of solid material with heat exchange mainly via its top ( U top ∼ 3.5 W/(m 2 K), overall heat transfer coefficient) and some heat exchange ( U side ∼ 0.29 W/(m 2 K)) through its cylindrical and bottom part. With this “modified cylinder” model (being neither an infinitely long cylinder nor a slab) of the Dewar vessel, we found that the UN method H.4 enables an accurate prediction of the SADT, with small deviations of 0 ± 2.5 °C. Further, by performing a truly three-dimensional (3D) finite element calculation in FEMLAB, the new heat characteristics of the Dewar vessel as well as a 50 kg package of dilauroyl peroxide, a solid organic peroxide, were checked. The outcome was compared with the critical ambient temperatures known for various package sizes, which agreed well.

Substitution of β‐Nitrostyrenes by Electrophilic Carbon‐Centered Radicals.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Substitution of β-nitrostyrenes by electrophilic carbon-centered radicals

Various trans-β-alkylstyrenes (55–90% yield) were isolated from the free radical addition/elimination process of α-iodocarboxylic acid derivatives with β-nitrostyrenes using dilauroyl peroxide as initiator. The corresponding xanthates give low yields of the alkene under similar conditions.

Carbon-carbon bond formation by radical addition-fragmentation reactions of O-alkylated enols.

Alpha-tert-butoxystyrene [H2C=C(OBut)Ph] reacts with alpha-bromocarbonyl or alpha-bromosulfonyl compounds [R1R2C(Br)EWG; EWG =-C(O)X or -S(O2)X] to bring about replacement of the bromine atom by the phenacyl group and give R1R2C(EWG)CH2C(O)Ph. These reactions take place in refluxing benzene or cyclohexane with dilauroyl peroxide or azobis(isobutyronitrile) as initiator and proceed by a radical-chain mechanism that involves addition of the relatively electrophilic radical R1R2(EWG)C* to the styrene. This is followed by beta-scission of the derived alpha-tert-butoxybenzylic adduct radical to give But*, which then abstracts bromine from the organic halide to complete the chain. Alpha-1-adamantoxystyrene reacts similarly with R1R2C(Br)EWG, at higher temperature in refluxing octane using di-tert-amyl peroxide as initiator, and gives phenacylation products in generally higher yields than are obtained using alpha-tert-butoxystyrene. Simple iodoalkanes, which afford relatively nucleophilic alkyl radicals, can also be successfully phenacylated using alpha-1-adamantoxystyrene. O-Alkyl O-(tert-butyldimethylsilyl) ketene acetals H2C=C(OR)OTBS, in which R is a secondary or tertiary alkyl group, react in an analogous fashion with organic halides of the type R1R2C(Br)EWG to give the carboxymethylation products R1R2C(EWG)CH2CO2Me, after conversion of the first-formed silyl ester to the corresponding methyl ester. The silyl ketene acetals also undergo radical-chain reactions with electron-poor alkenes to bring about alkylation-carboxymethylation of the latter. For example, phenyl vinyl sulfone reacts with H2C=C(OBut)OTBS to afford ButCH2CH(SO2Ph)CH2CO2Me via an initial silyl ester. In a more complex chain reaction, involving rapid ring opening of the cyclopropyldimethylcarbinyl radical, the ketene acetal H2C=C(OCMe2C3H5-cyclo)OTBS reacts with two molecules of N-methyl- or N-phenyl-maleimide to bring about [3 + 2] annulation of one molecule of the maleimide, and then to link the bicyclic moiety thus formed to the second molecule of the maleimide via an alkylation-carboxymethylation reaction.

Oxidative Radical Cyclization on Enamide Systems Using n‐Bu3SnH and Dilauroyl Peroxide.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Oxidative radical cyclization on enamide systems using n-Bu 3SnH and dilauroyl peroxide

Efficient 5- endo and 6- endo oxidative radical cyclizations on enamide systems are described using nBu 3SnH and dilauroyl peroxide both as initiator and oxidant. Dibenzoyl peroxide and dicumyl peroxide were also tested in the same reaction and the product yields were very similar to those obtained with dilauroyl peroxide. The erythrina ring system was constructed in a two-step sequence featuring this novel process.

Solid Phase Modification of Poly(propylene). The Role of the Polymer Texture in the Peroxide Distribution

Different poly(propylene)s were reacted with tert-butyl peroxybenzoate (TBPB) in solid phase and the time dependence of the concentration of tertiary polymer radicals ([A∗︁]) formed was measured by ESR spectroscopy at 145°C. The distribution (or solubility) of peroxide was found uneven (or limited), the segregation of solid dilauroyl peroxide (DLPO) was proved by DSC. It was found that not the crystalline/amorphous ratio was the decisive factor in poly(propylene)/peroxide solid phase reactions, but much more the crystallite size of the polymer texture. The latter was determined by X-ray measurements. Poly(propylene)s with average crystallite diameters of about 250 Å showed a characteristic dependence on peroxide concentration in the solid phase reaction of tertiary carbon radical forming. The log [A∗︁] vs. time curves show a good linearity, the relationships correspond to a unimolecular overall kinetics. When the crystallite diameters were 17–40% less than 250 Å, the polymer radical concentration ([A∗︁]) did not show a characteristic dependence on TBPB concentration. Our findings are interpretable in terms of capillary condensation of peroxides.