A New Synthesis of Substituted Ninhydrins

Suggest a simple synthesis of 1 and a mechanism for the oxidation of 1 to the ninhydrin. 

In an attempt to prepare the stilbene (1), the dihydropyridine (2) was pyrolysed at 180°C at 0.1mm. The products obtained, however, were m-chlorostyrene (82%) and 2,4,6-triphenyl-pyridine. 

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