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The bromination of helically folded oligoamides of 8-amino-4-isobutoxy-2-quinolinecarboxylic acid by N-bromosuccinimide has been investigated. Bromination occurs preferentially if not exclusively at one position in the sequence despite the presence of multiple, up to seven, a priori comparable, reaction sites. Reactions are up to 2 orders of magnitude faster in a folded octamer than in a short nonhelical dimer, despite the steric hindrance that is expected in a compact folded conformation. The presence of substituents remote from the reaction site have considerable influence, resulting in the loss of regioselectivity, or in the slowing down of the reaction by several orders of magnitude.

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 α,β-unsaturated esters with a wide variety of dienes. In contrast to many metal derived Lewis acids, TMSNTf2 was found tolerant of many sensitive functional groups present in the diene partner. [Copyright &y& Elsevier]