Shinzo Seko

Photoinduced molecular transformations. Part 135. New synthesis of taiwanin C and justicidin E based on a radical cascade process involving β-scission of alkoxyl radicals generated from 3- and 8-aryl-1-ethyl-1,2-dihydrocyclobuta[b]naphthalen-1-ols prepared by thermolysis of (Z)-tert-butyl 3-amino-3-(bicyclo[4.2.0]octa-1,3,5-trien-7-yl)propenoates

A new general synthesis of naturally occurring phthalide lignans, based on a radical cascade process triggered by a regioselective β-scission of the alkoxyl radicals generated by photolysis of the hypoiodites of 8-aryl-1-ethyl-1,2-dihydrocyclobuta[b]naphthalen-1-ols, is described. Two phases are involved in the present synthesis of phthalide lignans; the first is a new general synthesis of tert-butyl 4-aryl-3- and 4-aryl-8-aminonaphthalene-2-carboxylates by an electrocyclic reaction of o-quinonedimethides thermally generated from (Z)-tert-butyl 3-amino-3-(bicyclo[4.2.0]octa-1,3,5-trien-7-yl)propenoates; the second is a transformation of the protected 4-aryl-3-aminonaphthalene-2-carboxylic acids into the phthalide lignans. This latter phase involves their successive conversions into 3- and 8-arylcyclobuta[b]naphthalen-1 (2H)-ones via the formation of a benzyne intermediate, and then into 3- and 8-aryl-1-ethyl-1,2-dihydrocyclobuta[b]naphthalen-1-ols, followed by β-scission of the alkoxyl radicals generated by photolysis of their hypoiodites, generated in situ with the mercury(II) oxide–iodine reagent in benzene. Simultaneous syntheses of the naturally occurring phthalide lignans taiwanin C and justicidin E were thus achieved.

One-step formation of furo[3,2-c]quinolin-4(5H)-ones by a new regioselective [2+3] photoaddition of methoxy-substituted 4-hydroxyquinolin-2-one with alkenes1

Abstract Furo[3,2-c]quinolin-4(5H)-ones carrying one or more methoxyl group at their 5, 6, or 8 position can be obtained in yields of up to 60% using a one-step procedure involving an unprecedented [2+3] photoaddition between 5-, 7-, or 8-methoxy-4-hydroxyquinoline-2-one and an alkene in the presence of a benzophenone.

A convenient copper-catalyzed direct amination of nitroarenes with O-alkylhydroxylamines

O-Alkylhydroxylamines, particularly O-methylhydroxylamine, aminate nitroarenes in the presence of a strong base and a copper catalyst to give aminonitroarenes in good yields. ortho- or para-Amination with respect to the nitro group takes place, and in some cases the ortho-aminated product is preferentially obtained. With 3-substituted nitrobenzenes where the substituent has a lone pair of electrons, preferential amination occurs at the 2-position to give the sterically most congested 3c–f, 14 and 22g.

New general synthesis of tert-butyl 3-amino-2-naphthalenecarboxylates by an electrocyclic reaction of o-quinonedimethides generated from tert-butyl (Z)-3-amino-3-(bicyclo[4.2.0]octa-1,3,5-trien-7-yl)prop-2-enoates

A new general synthesis of tert-butyl 3-amino-2-naphthalenecarboxylates by an electrocyclic reaction of o-quinonedimethides thermally generated from tert-butyl (Z)-3-(bicyclo[4.2.0]-octa-1,3,5-trien-7-yl)prop-2-enoates is described.