Takaaki Horaguchi

A mild and efficient procedure for α-bromination of ketones using N-bromosuccinimide catalysed by ammonium acetate

Cyclic ketones reacted with N-bromosuccinimide (NBS) catalysed by NH(4)OAc in Et(2)O at 25 degrees C to give the corresponding alpha-brominated ketones in good yields, while acyclic ketones were efficiently brominated in CCl(4) at 80 degrees C.

Photoinduced electron transfer reactions of α,β-epoxy ketones with 2-phenyl-N,N-dimethylbenzimidazoline (PDMBI): Significant water effect on the reaction pathway

Abstract Irradiation of aroyl substituted epoxy ketones with 2-phenyl-N,N-dimethylbenzimidazoline in aqueous tetrhhydrofuran or aqueous benzene produced the corresponding aldols in good to excellent yields. Changing the amount of water addedsignificantly influenced the product distribution.

Selective Cα-O bond cleavage of chalcone epoxides induced by pyrylium salt sensitized photoreactions and dark reactions with cerium(iv) salts

The Cβ-O bonds of chalcone epoxides (1a, 1b) were selectively cleaved by pyrylium salt sensitized photoreactions, affording β-ketoaldehydes (2a, 2b) in CH2Cl2 and MeOH-adducts (3a, 3b) in MeOH. Similarly. cerium(IV) salts catalyzed the MeOH-adduct formations of 1a and 1b in the dark. On the other hand, nitrate ester (4b) was obtained on treatment of 1b with a cerium(IV) salt in MeCN.

Free radical trapping of α-keto radicals derived from α,β-epoxy ketones via photoinduced single electron transfer process

Abstract Irradiation of aromatic α,β-epoxy ketones in the presence of allyltributyltin afforded α-allyl-β-hydroxy ketones by a single electron transfer mechanism.

A mild and efficient method for the mononitration of aromatic compounds by cerium (III) ammonium nitrate in acetic anhydride

A mild and efficient method for the mononitration of aromatic and olefinic compounds is described. This method is especially useful for active substrates.

Reactions of 1-bromo-2,3-epoxypropane with samarium diiodide: First observation of carbon-carbon bond cleavage of oxiranylmethyl radical under the single electron transfer conditions

Abstract Reaction of 1-bromo-1-phenyl-3-(1-naphthyl)-2,3-epoxypropane 1 with samarium diiodide afforded 1-phenyl-2-(1-naphthylmethoxy)ethene 3 as well as 1-(1-naphthyl)-3-phenylprop-2-enol 2. The product distributions were influenced by various factors, such as additives, concentrations, and reaction temperature.

Selective Cα–O bond cleavage of α,β-epoxy ketones to aldols induced by free radical processes

Several α,β-epoxy ketones were converted to aldols in good yields upon irradiation or heating with azoisobutyronitrile in the presence of tributyltin hydride in benzene; the reactions involve selective Cα–O bond cleavage of the oxiranylmethyl radicals derived from these substances.

Chemoselective Reduction of Aldehydes in the Presence of Ketones with NaBH4 in Polyethylene Glycol Dimethyl Ethers

Abstract Aldehydes and ketones were treated with NaBH4 in polyethylene glycol dimethyl ethers (PEGDME) to give the corresponding alcohols in good yields. Chemoselective reduction of aldehydes in the presence of ketones was described.

Novel photoreaction of 4-tribromomethyl-4-methyl-2,5-cyclohexadienone with amine

Abstract Irradiation of 4-tribromomethyl-4-methyl-2,5-cyclohexadienone in the presence of amines gave 4-bromo-5-methyltropone as a major product. On the basis of the results obtained, the mechanism involving single electron transfer from the amine ground state to the dienone excited state was proposed.

2,3-Dichloro-5,6-dicyano-p-benzoquinone as a mild and efficient catalyst for the deprotection of acetals

In the presence of a catalytic amount of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), acetals are readily hydrolysed to the corresponding aldehydes or ketones in aqueous acetonitrile under neutral conditions.