N-trimethylsilyl bis (trifluoromethanesulfonyl) imide (TMSNTf2) was readily prepared in situ by protodesilylation of trimethylsilane, allyl-or phenyltrimethylsilane with bis (trifluoromethylsulfonyl) imide. NMR studies showed that TMSNTf2 was much more effective than TMSOTf in complexing the carbonyl group of trans-methylcrotonate. As a result, TMSNTf2 was found to be superior to TMSOTf as a catalyst for the Diels–Alder reaction of ...