REACTIONS OF PHENYLTRIAZOLINEDIONE WITH ALKENES - STEREOCHEMISTRY OF METHANOL ADDUCTS TO AZIRIDINIUM IMIDE INTERMEDIATES

The addition of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) and the ste reochemistry of methanol/PTAD adduct formation with cis- and trans-2-b utenes, 1-methylcyclopentene, (E)-2-methyl-2-butene-1,1,1-d(3), and su bstituted indenes (indene, 2-methylindene, 2,3-dimethylindene) have be en investigated. There is no loss of stereochemistry in the addition o f MeOH and PTAD to butenes, 1-methylcyclopentene, 2-methyl-2-butene, a nd indene. However, in methyl-substituted indenes 9 and 14, loss of st ereochemistry at the reaction center is observed. An aziridinium imide (AI) is proposed as an intermediate in all these systems. The stabili ty of the AI intermediate and its equilibration with an open zwitterio n depend on the particular system. Only in the benzylically-stabilized tertiary indenes is the open zwitterion stable enough to cause loss o f stereochemistry.