Takahito Muraki

Remote functionalization (1): Synthesis of γ- and δ-lactones from aromatic carboxylic acids

Oxidative cyclization of o-alkyl- or o-arylaromatic carboxylic acids with [bis(trifluoroacetoxy)iodo]benzene and iodine via aromatic carbonyloxy radicals gave the corresponding lactones in good yields.

REMOTE FUNCTIONALIZATION : CYCLIC ALKOXYLATION ONTO AROMATIC RING VIA RADICAL PATHWAY

Abstract Oxidative cyclization of alcohols containing an aromatic ring with (diacetoxyiodo)benzene and iodine gave the corresponding cyclic ethers via alkoxy radicals in good yields. The present method is very useful for the direct preparation of flavonoid and vitamin E analogues from the alcohols.

Formation and synthetic use of oxygen-centred radicals with(diacetoxyiodo)arenes

o-Alkyl- or o-aryl-benzenecarboxylic acids and alcohols containing an aromatic ring are treated with a (diacetoxyiodo)arene–iodine system to give the corresponding cyclized products such as phthalide, benzocoumarin and chromane derivatives in moderate to good yields via the corresponding oxygen-centred radicals. For the carboxylic acids, [bis(trifluoroacetoxy)iodo]benzene functions effectively, while (diacetoxyiodo)benzene is effective for the alcohols. Chromane and its derivatives are obtained as iodinated compounds by hypoiodite species derived from (diacetoxyiodo)benzene and iodine.

Reactivity in the formation of lactones from aromatic carboxylic acids with organohypervalent iodine compounds in the Suárez system

The reactivity of various iodanes, such as (diacetoxyiodo)arenes, the Dess–Martin reagent, and (arylsulfonyloxy)benziodoxolones, with (o-alkyl)- and (o-phenyl)arenecarboxylic acids in the presence of iodine (Suarez system) was studied to give the corresponding lactones via oxygen-centered radicals. (Diacetoxyiodo)arenes gave the lactones in good yields, while 1-(arylsulfonyloxy)benziodoxolones gave lactones together with the iodinated lactones. The Dess–Martin reagent also showed the same reactivity as (diacetoxyiodo)arenes to give the lactones. Among them, (diacetoxyiodo)toluene showed the best reactivity for the conversion of these carboxylic acids to the corresponding lactones.