Kazu Kurosawa

Formation of 1,2-dioxacyclohexanes by the reaction of alkenes with tris(2,4-pentanedionato)manganese(III) or with β-ketocarbonyl compounds in the presence of manganese(III) acetate

Abstract The reactions of 1,1-disubstituted ethenes, styrene, 1-octene, 1-nonene, cyclohexene and cyclooctene with tris(2,4-pentanedionato)manganese(III) in acetic acid at room temperature give 4-acetyl-3-hydroxy-3-methyl- 1,2-dioxacyclohexanes in 8–92 % yields. The reactions of 1,1-disubstituted ethenes with ethyl 3-oxobutanoate or acetoacetanilide in the presence of manganese(III) acetate also give cording 1,2-dioxacyclohexanes in good to moderate yields.

Manganese-(II) and (III)-mediated free-radical cyclisation of alkenes, β-keto esters and molecular oxygen

The reactions of substituted ethenes with β-keto esters in the presence of a mixture of manganese(II) and manganese(III) acetates, and molecular oxygen yielded substituted 1, 2-dioxan-3-ols 3 in 14–95% yields. Cobalt(III) acetate, potassium permanganate, lead(IV) acetate, copper(II) acetate, chromium(VI) trioxide, thallium(III) acetate, ammonium cerium(IV) nitrate and iron(III) perchlorate were also used in place of manganese(III) acetate. Effects on the product yields of substituents in the alkenes and β-keto esters have been examined and reaction mechanisms are discussed.

Mn(III)-based reactions of alkenes and alkynes with thiols. An approach toward substituted 2,3-dihydro-1,4-oxathiins and simple route to (E)-vinyl sulfides

Abstract The first example using manganese(III) acetate in the reaction of 1,1-diarylethenes with α-mercaptoketones was examined. A mixture of the ethenes and α-mercaptoketones was treated with manganese(III) acetate in acetic acid, affording cycloaddition products in moderate yields, together with substituted products. The reaction may involve the formation of a carbocation and subsequent cyclization to give the substituted 2,3-dihydro-1,4-oxathiin 3 . A similar reaction with thioglycolic acid gave 1,4-oxathiolan-2-one 7 . While thiyl radicals easily formed by manganese(III) oxidation with ethanethiol or benzenethiol reacted with alkynes to give preferentially ( E )-vinyl sulfides 10 in quantitative yields.

Mn(III)-Induced molecular oxygen trapping reaction of alkenes with 2,3-pyrrolidinedione derivatives. A novel entry to 1-hydroxy-8-aza-2,3-dioxabicyclo[4.3.0]nonan-9-ones

Abstract Molecular oxygen trapping reaction of alkenes with 2,3-pyrrolidinedione derivatives was developed using a Mn(III)-induced oxidation system. Alkenes and 2,3-pyrrolidinediones were treated with manganese(III) acetate in acetic acid under a stream of dry air, giving 1-hydroxy-8-aza-2,3-dioxabicyclo[4.3.0]nonan-9-ones in good yields. The reaction involved molecular oxygen trapping of radicals which were formed by the addition of pyrrolidinedione radicals induced by Mn(III) to alkenes.

Catalytic oxidation of 4-piperidone-3-carboxylates with manganese(III) acetate in the presence of 1,1-disubstituted alkenes

Abstract The manganese(III) acetate-catalyzed cycloperoxidation of 4-piperidone-3-carboxylates with 1,1-disubstituted alkenes is described. The 4-piperidone-3-carboxylates reacted with 1,1-disubstituted alkenes in the presence of a catalytic amount of manganese(III) acetate in air at 23°C to give 1-hydroxy-8-aza-2,3-dioxabicyclo[4.4.0]decane-6-carboxylates in good to moderate yields. The crystal structure of the azabicyclic peroxides was determined by an X-ray single crystal analysis. The oxidation of the 4-piperidone-3-carboxylates with 1,1-diphenylethene using a stoichiometric amount of manganese(III) acetate gave ethenyl- and ethyl-substituted 4-piperidones and 6-hydroxy-3-aza-7-oxabicyclo[4.3.0]nonane-1-carboxylate, which was the same as the product obtained from the hydrogenolysis of the 1-hydroxy-8-aza-2,3-dioxabicyclo[4.4.0]decane-6-carboxylate.

Acid-catalyzed convenient transformation of 1-aryl-2-pentene-1,4-diones into polyfunctionalized furans

Abstract The reaction of phenylglyoxal with 2,4-pentanedione in the presence of boron trifluoride gave the unstable 3-acetyl-1-phenyl-2-pentene-1,4-dione intermediate which was converted in situ by the reaction with an excess amount of 2,4-pentanedione into new crystalline tri- and tetra-substituted furans. Other unstable 1-aryl-2-pentene-1,4-diones, which were obtained by the photooxygenation of 3-acetyl-5-aryl-2-methylfurans, were trapped by the acid-catalyzed reaction, giving polyfunctionalized furans in good yields. Treatment of the 1-phenyl-2-pentene-1,4-dione intermediate with concentrated hydrochloric acid followed by boiling ethanol quantitatively yielded a stable 2-ethoxymethylfuran via the unstable 2-chloromethylfuran.

Convenient synthesis of 3-cyano-4,5-dihydrofurans and 4-cyano-1,2-dioxan-3-ols using acylacetonitrile building block

Abstract Acylacetonitriles were easily oxidized with manganese(III) acetate in acetic acid to form the corresponding acylcyanomethyl radicals, which attacked alkenes at reflux temperature to give new 3-cyano-4,5-dihydrofurans and at the room temperature under air to yield new 4-cyano-1,2-dioxan-3-ols in good yields.

Synthesis of naphthalenes using acid-catalyzed ring-opening and recyclization of 3-acetyl-5,5-diaryl-2-methyl-4,5-dihydrofurans. Isolation of intermediates

3-Acetyl-5,5-diaryl-2-methyl-4,5-dihydrofurans were heated in concentrated hydrochloric acid to give the 4-aryl-1-methylnaphthalenes in high yields. The same reaction was carried out in hydrochloric acid diluted with acetonitrile to give the 5,5-diaryl-4-penten-2-ones (87–96%), while treatment of the dihydrofurans with p-toluenesulfonic acid in acetonitrile afforded the 3-(2,2-diarylethenyl)-4-hydroxy-3-penten-2-ones (73–91%) which were transformed in diluted hydrochloric acid into the 5,5-diaryl-4-penten-2-ones. It was demonstrated that the 3- and 4-penten-2-ones were intermediates of the 4-aryl-1-methylnaphthalenes since the 3- and 4-penten-2-ones were easily converted into the corresponding naphthalenes in concentrated hydrochloric acid. The UV irradiation of the dihydrofurans in the presence of hydrochloric acid quantitatively gave the 2-acetyl-4-aryl-1-methylnaphthalenes (94–97%) via the same 3-penten-2-one intermediates.

Photooxygenation of 3-acetyl-5-aryl-2-methylfurans via endoperoxide intermediate and the following reactions

The photooxygenation of 3-acetyl-5-aryl-2-methylfurans 1a–e selectively produced 2,2-diacetyl-3-aroyloxiranes 2a–e, 3-acetyl-1-aryl-2-pentene-1,4-diones 3a–e, and 3-acetyl-1-aryl-2-hydroxy-2-pentene-1,4-diones 4a–d via the endoperoxide intermediate A depending on the reaction conditions and the work-up procedure. The oxiranes 2a–e were mainly obtained in 56–77% yields by allowing the reaction mixture to stand at ambient temperature after the irradiation, while the treatment of the reaction mixture with water mainly gave the 1,4-diones 3a–e (62–69%). Heating the reaction mixture at 80°C after the irradiation decreased the total yield of the products, however, the enols 4a–d were newly formed in 8–12% yields. Direct UV irradiation of the endoperoxide intermediate A led to the homolytic fission of the peroxide linkage to produce the same enols 4a–e (16–39%). The self-sensitized photooxygenation of 1a–d using a UV light also gave 4a–d in a similar yield. The reaction pathway is discussed based on these results.

A novel macrodiolide synthesis using the Mn(III)-based radical cyclization of terminal alkadienes and oligomethylene Di(3-oxobutanoate)s

Abstract α,α,ω,ω-Tetraphenyl-α,ω-alkadienes reacted with oligomethylene di(3-oxobutanoate)s in the presence of manganese(III) acetate at 100 °C under an argon atmosphere to give new 12 to 22-membered macrocyclic compounds which were two fused dihydrofuran rings in a one-step procedure.