Photodecarboxylative benzylations of phthalimide in pH 7 buffer: a simple access to 3-arylmethyleneisoindolin-1-ones

Photoadditions of phenylacetates to phthalimide in pH 7 buffer solution give the corresponding benzylated-hydroxyphthalimidines in moderate to high yields of up to 94%. In a micro-structured reactor, higher conversions and purities are achieved. With branched phenylacetates, photoaddition affords diastereoisomeric mixtures with low to moderate de values. Subsequent acid-catalyzed dehydration furnishes the corresponding 3-arylmethyleneisoindolin-1-ones in good to excellent yields and with high E-selectivities. Irradiation of the parent 3-phenylmethyleneisoindolin-1-one under oxidative conditions only leads to cis/trans-isomerization.