Isotope effects and syn selectivity in the ene reaction of triazolinedione with conjugated enones: aziridinium imide or an open intermediate mechanism?
The ene reaction of 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) with phorone-d(6) (5-d(6)) shows an inverse beta-secondary isotope effect and with mesityl oxide-d(3) (7-d(3)) proceeds with 93% syn selectivity. These results are consistent with a mechanism involving the formation of an aziridinium imide intermediate in the rate-determining step. An open biradical or dipolar intermediate is excluded by them.
Department of Chemistry, University of Crete, 71409 Iraklion, Crete, Greece.
G
Vassilikogiannakis
M
Stratakis
M
Orfanopoulos