Masahito Itoh

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 synthesis of phthalides through β-scission of benzocyclobutenol hypoiodites☆

Abstract A simple new method for the synthesis of phthalides and their 3-alkyland 3,3′-spiroalkyl derivatives including (±)-3-butylphthalide, a racemic form of a constituent of celery oil, through the β-scission of alkoxyl radicals generated from hypoiodites of benzocyclobutenols by the photolysis, is described.

Photo-induced molecular transformations. Part 87. Ring expansion through [2 + 2] photocycloaddition-β-scission sequences; synthesis of benzohomotropones from 1- and 2-naphthols and methyl acrylate

Photolysis of 4-substituted tricyclo[6.4.0.02,5]dodeca-1(12),6,8,10-tetraen-5-ols (9), (10), and (12), derived in three-steps from the regioselective photocycloadducts formed from 2-naphthyl trimethylsilyl ether and methyl acrylate, in the presence of HgO–I2 in benzene, to give the benzocyclo-octenone derivatives (11), (13), and (14) which arise from β-scission of their fused bond. The benzocyclo-octenones cyclized with base in DMF to give benzohomotropones, 4-substituted tricyclo[6.4.0.02,4]dodeca-1(12),6,8,10-tetraen-2-ones (15) and (16). Similar photolyses of 3-substituted tricyclo[6.4.0.02,5]dodeca-1(12),6,8,10-tetraen-2-ols (24) and (25), prepared in three steps from the regioselective [2 + 2] photocycloadduct (19) formed from 1-naphthyl trimethylsilyl ether with methyl acrylate, in the presence of HgO–I2 in benzene, gives the benzocyclo-octenone (26) in rather low yield. Treatment of the latter with a base in DMF gave a benzohomotropone, 3-substituted tricyclo[6.4.0.03,5]dodeca-1(12),6,8,10-tetraen-2-one (27).

Photoinduced molecular transformations. Part 138. A new route to dibenzo[a,d]cycloalkanes and their naphtho analogues via the ring expansion of benzocyclobutenols involving a selective β-scission of cyclobutenoxyl radicals generated by photolysis of their hypoiodites

A new synthesis of several funtionalized dibenzo[a,d]cyclooctanes, dibenzo[a,d]cyclononanes, and their naphtho analogues is described. This synthesis involves the ring expansion of benzocyclobutenols by a selective β-scission of the cyclobutenoxyl radicals generated by photolysis of their hypoiodites.

New short step synthesis of A,B-aromatic oxasteroids by intra- and intermolecular Diels–Alder reactions of 1,2-naphthoquinone dimethides generated from substituted 1,2-cyclobutanaphthalenes

A simple, highly efficient synthesis of A/B aromatic 16-oxasteroids by either an intra- or inter-molecular Diels–Alder reaction of 1,2-naphthoquinone dimethides, generated by the thermolysis of methyl cyclobuta [a] naphthalene- 2-carboxylate or cyclobuta [a]naphthalen-2-ylmethanol, is described.