Silylative Dieckmann-Like Cyclizations of Ester-Imides (and Diesters)

Trialkylsilyl triflates effect cyclization of ester-imides such as 2 to produce adducts such as 4a. Trapping of the in situ generated, nucleophilic
ketene acetal (cf. 5a) is a key aspect of the transformation. A range of substrates amenable to this operationally simple reaction is reported.
In many instances the levels of diastereoselectivity are very high. Mechanistic points are inferred from spectroscopic observations.