Phthalimidines, conversion into isoindoles

Phthalimidines (isoindolin-l-ones) can be valuable intermediates for the synthesis of isoindoles and some natural products, and there has been recent interest in the development of simple methods for the direct conversion of o-phthalaldehyde into /V-substituted phthalimidines. Condensation of o-phthalaldehyde with primary aliphatic amines using acetonitrile as solvent gives disappointing yields with a-methylbenzylamine, for example, the yield of the phthalimidine 1 is only 21%. By contrast, treatment of o-phthalaldehyde with a-amino acids in hot acetonitrile gives generally excellent yields of the corresponding phthalimidines. With L-valine, for example, 2 is formed in 87% yield. 

An interesting example of electrophilic substitution is the conversion of phthalimidine (2,3-dihydro-l/f-isoindol-l-one) into l-bromo-3-formyhsoindole under Vilsmeier conditions (formation of 1-bromo-2//-isoindole may be the first step)." Mannich substitution of 2-methyl-l-phenylisoindole is another straightforward example. ... 

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See also in sourсe #XX -- [ , , ]

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