Tandem zinc-carbenoid mediated chain extension-aldol chemistry of beta-carbonyl imides

Synthetic sequences to prepare gamma-methoxy beta-keto imides and malonyl diimides were investigated in an effort to expand the scope of the tandem zinc-mediated chain extension aldol reaction. The chain extension-aldol reaction of the gamma-methoxy beta-keto imide proceded smoothly, although low stereoselectivity of the reaction was observed. The chain extension of malonyl diimides were slow when compared to traditional substrates. The chain extension-aldol reaction of malonyl diimides provided gamma-lactones with moderate yield and selectivity in a one-pot reaction sequence. Due to the extended chain extension reaction times, reduction of aldehydes was observed during attempted aldol reactions. A chain extension aldol protocol, specific for the application to malonyl diimides, was developed to reduce the appearance of products resulting from the reduction of the respective aldehyde