Phthalaldehydes, isomeric

In the course of polarographic and spectrophotometric investigations of isomeric phthalaldehydes, it has been observed that substituted benzaldehydes... 

A study of the matrix-isolated photochemical behaviour of o-phthalaldehyde has identified two isomeric forms only one of which, the -Z-isomer (351), is photochemically reactive. Irradiation of this at 313nm yields the E- and Z-isomers (352) and (353). The -isomer can be photochemically converted by... 

In the case of aromatic dialdehydes, the cyclization is frequently accompanied by dehydration Thus, o-phthalaldehyde cyclizes when treated with nitromethane in the presence of alcoholic potassium hydroxide (Scheme 6) to give the flci-nitro salt that undergoes dehydration by acidification with mineral acid to form 2-nitroinden-l-ol (35). This reaction was discovered in 1910 by Thiele and Weitz and can be considered the first demonstrated example of the cyclization of a dialdehyde with nitromethane. Like o-phthalaldehyde, naphthalene-2,3-dicarbaldehyde and o-benzoylbenzaldehyde undergo ready cyclization with nitromethane under similar reaction conditions to form respectively, 2-nitrobenzinden-l-ol (equation 7) and two isomeric o-nitrohydroxyindenes (36) and (37) (equation 8) upon acidification with mineral acid. The cyclization with nitromethane also works well with suitable diketones such as bicy-clo[3.3.1]nonane-3,7-diones where the carbonyl groups are favorably oriented for cyclization on treatment with nitromethane and sodium methoxide the corresponding 2-nitroadamantane-l,3-diols (equation 9) are obtained in fair to good yields. 

Other examples of addition to the oxygen atom in the Cy5/Cy4 case have been observed with acyl radicals, generated by photolysis of o-phthalaldehyde, " " or of aryl phthalates " (X = O) and thiophthalates (X = S) (194). Isomerized products (196) (X = O) or coupling products (X = S) from 195 have been rationalized according to Scheme 85. As in the preceding... 

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