Keiko Kuroda

A convenient synthesis of 1-bromoolefins and acetylenes by a chain extension of aldehydes

Abstract Aldehydes are easily converted to 1-bromoolefins or terminal acetylenes by the use of Wittig reaction of bromomethylenetriphenylphosphorane which is prepared from bromomethyltriphenylphosphonium bromide with potassium tert-butoxide.

Sensitized photo-oxygenation of acyclic conjugated dienes

Abstract Sensitized photo-oxygenation of a wide variety of acyclic 1,3-dienes was investigated. The 1,4-cycloaddition of singlet oxygen to acyclic conjugated dienes was closely related to the thermal Diels-Alder reaction in stereospecificity, and steric and electronic effects of substituents. Reactivity order of singlet oxygen toward conjugated dienes and isolated C—C double bonds was exhibited as follows: trisubstituted mono-olefins > 2-substituted 1,3-dienes > disubstituted mono-olefins.

Transition metal(ii) schiff's base complexes catalyzed oxidation of trans-2-(1-propenyl)-4,5-methylenedioxyphenol to carpanone by molecular oxygen

Abstract Carpanone was synthesized in an excellent yield by the oxidation of trans -2- (1-propenyl) -4,5-methylenedioxyphenol with molecular oxygen in the presence of transition metal complexes such as Co(II)salen, Co(II)salpr, Fe(II)salen, and Mn(II)salen.

Solvent Effect in Reaction of Singlet Oxygen with Conjugated Dienes

Abstract The 1,4-cycloaddition of singlet oxygen (1O2) to conjugated dienes provides a useful tool for simultaneous functionalization of the diene moiety, and its application to organic synthesis has been reported.1 For the dienes bearing an allylic hydrogen, especially for the dienes not constrained to s-cis conformation, the 1,4-cycloaddition usually competes with the “ene” reaction as well as the 1,2-cycloaddition.2 The efficiency of the oxygenation3 and the selectivity of the reaction modes are essential factors in the synthetic application. We have investigated the sensitized photooxygenation of representative acyclic dienes and vinylarenes i n various solvents.

Sensitized photooxygenation of β-methoxystyrene and 1-(β-methoxyvinyl)naphthalene

Single oxygen can easily add to 1-(β-methoxyvinyl) naphthalene (1) with retention of sterochemistry to afford a stable 1,4-endoperoxide 3. Sensitized photooxygenation of β-methoxystyrene (2) gives mainly Diels-Alder adducts of o-formylmethide quinone (12) which might be derived from initially formed 1,4-endoperoxide 10.

The 1,4-addition of singlet oxygen to 2,6-dimethoxy-1-(2-methoxyethenyl) benzene and 2-methoxy-1-(2-methoxyethenyl)naphthalene. The 1,4-endoperoxides as equivalents of 6-oxo-2,4-cyclohexadienylidenacetates.

Abstract The sensitized photooxygenation of vinylarenes 1 and 2 gave the corresponding 1,4-endoperoxides which were decomposed under mild conditions into quinone methides bearing ester function at the exocyclic carbon.

Sensitized photooxygenation of 2,4-hexadienoic acid esters and 2,4,6-octatrienoic acid esters. Unusual solvent and temperature effects

Abstract Sensitized photooxygenation of the title compounds were remarkably affected by the solvent used and the reaction temperature.