Akiyoshi Sasaki

New short step general synthesis of isobenzofuran-1(3H)-ones (phthalides) based on a single or double β-scission of alkoxyl radicals generated from 1-ethyl-benzocyclobuten-1-ols and from 1,3-dihydroisobenzofuran-1-ols; synthesis of some natural phthalides

Abstract New general methods are described for the synthesis of phthalides, 3-monosubstituted, and 3,3-disubstituted phthalides including naturally-occurring phthalides such as pierardine based on a regioselective single or double β-scission of the alkoxyl radicals generated by the photolysis of the hypoiodites of 1-ethyl benzocyclobuten-1-ols or 1,2-catacondensed benzocyclobuten-1-ols or 1,3-dihydro-1,3-alkanoisobenzofuran-1-ols. The formation paths of the phthalides, which involve a regioselective single or double β-scission of the alkoxyl radicals generated from 1-alkylbenzocyclobuten-1-ols and from catacondensed benzocyclobuten-1-ols, are discussed.

A new route to γ-substituted γ-lactones and δ-substituted δ-lactones based on the regioselective β-scission of alkoxyl radicals generated from transannular hemiacetals

Abstract A new general synthesis of γ-substituted γ-lactones and δ-substituted δ-lactones including dihydro-5-octyl-2(3H)-furanone, a natural pheromone, is described. The synthesis involves the regioselective β-scission of alkoxyl radicals generated from transannular hemiacetals as the key step.

Photoinduced molecular transformations. Part 127. A new [2 + 2] photoaddition of 2-amino-1,4-naphthoquinone with vinylarenes and the synthesis of 2,3-dihydronaphtho[1,2-b]furan-4,5-diones and 2,3-dihydronaphtho[2,3-b]furan-4,9-diones by β-scission of alkoxyl radicals generated from the resulting photoadducts

Irradiation of 2-amino-1,4-naphthoquinone and excess of vinylarenes such as styrene, its para-substituted derivatives, 2-vinylpyridine and 4-vinylpyridine in benzene with a Pyrex-filtered light at room temperature under nitrogen gave 1-aryl-1,2,2a,8b-tetrahydro-8b-hydroxycyclobuta[a]naphthalene-3,4-diones as a single product in 23–63% yields, respectively. These cyclobutanols arise from an unprecedented stereo- and regio-selective [2 + 2] photoaddition of an excited enol form of 2-amino-1,4-naphthoquinone with the vinylarenes.Irradiation of these cyclobutanols in benzene containing excess of mercury(II) oxide and iodine with Pyrex-filtered light then gave 2-aryl-2,3-dihydronaphtho[1,2-b]furan-4,5-diones and/or 2-aryl-2,3-dihydronaphtho[2,3-b]furan-4,9-diones (31–73% yields) arising from a regioselective β-scission of the alkoxyl radicals, followed by intramolecular cyclization of the resulting radical intermediates. The substituent at the para position of the 1-phenyl group was found to control the ratio of the two types of products: a methoxy group directs the formation of the 4,5-dione exclusively, while the p-cyano group directs the formation of the 4,9-dione exclusively. This considerable dependence of the products on the substituents suggests that at least some part of the formation of the dihydrofuran ring of the 4,5 and/or 4,9-diones takes place from the ionic intermediates arising owing to β-scission. 2,3-Dihydronaphtho[1,2-b]furan-4,5-dione was found to isomerize to 2,3-dihydro[2,3-b]furan-4,9-dione on silica gel.

Photoinduced molecular transformations. Part 151. One-pot synthesis of 1H-benz[g]indole-4,5-diones by a regioselective (3+2) photoaddition of 4

Abstract 1 H -Benz[ g ]indole-4,5-diones are formed in up to 82% yields by the (3+2) photoaddition of 4-amino-1,2-naphthoquinone with alkyl vinyl ethers in