Sulfur ylides. 11. Selected chemical transformations of 1-methylthio-3,4-dihydropyrido[2,1-a]isoindole-2,6-dione

The reaction of 1-methylthio-3,4-dihydropyrido[2,1-a]isoindole-2,6-dione (2) with NaBH₄ led to reduction of the keto group to the hydroxy group. The reaction with the use of LiAlH₄ resulted in complete reduction of the carboximide group, reduction of the keto group to the hydroxy function, and reduction of the double bond accompanied by desulfurization. The reaction of indolizidinedione 2 with Zn afforded a reductive desulfurization product. The reactions of 2 with hydrazine hydrate, hydroxylamine, and formamide proceeded according to a mechanism typical of the keto group to give hydrazone, oxime, and the formyl derivative, respectively. Oxidation of the thiomethyl group of the starting compound with Bu^tOOH gave rise to sulfone or sulfoxide depending on the amount of the oxidizing agent used.