Takahachi Shimizu

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.

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.

Conformational effects in photocyclization of six and seven-membered ring alkoxyketones

Irradiation of 8-alkoxytetrahydro-1-naphthalenones 5 gave rearranged naphthyl alcohols 11 as major products and in contrast, 4-alkoxytetrahydrobenzocyclohepten-5-ones 6 afforded tetrahydrocyclohepta[cd]benzofurans 14 in good yields; the difference in reactivities is attributed to the conformation of six- and seven-membered rings.