Reactivity of 2-acylaminoacrylates with ketene diethyl acetal; [2 + 2] cycloadditions vs. tandem condensations

The reactivity of 2-acylaminoacrylates with ketene diethyl acetal can be modulated by means of thermal conditions to yield cyclobutanes for the preparation of protected (beta)-hydroxycyclobutane-(alpha)-amino acids, or catalytic conditions that yield cyclohexanes by tandem condensations to obtain interesting building blocks that are alternatives to Danishefskyʹs diene.