Synthesis of 2-carboxylated aza-ring derivatives through α-monohalogenation/ring-contraction of N-sulfonyl lactams

Synthesis of γ-substituted carbonyl compounds from DMSO-mediated oxidation of enynamides: mechanistic insights and carbon- and hetero-functionalizations

“…Esterification of these occurred chemoselectively to furnish the corresponding ε-alkoxydienoates 23 or γ-hydrazidoenoates 24 , respectively, in good yields (eqn (2)). The imide product 8ba could be converted into a Weinreb amide 25 under basic conditions (eqn (3)) 25. The ε-alkoxy-α,β,γ,δ-unsaturated imide 13ba underwent Diels–Alder cycloaddition with N -methyl maleimide to give 26 with an exclusive endo -selectivity and a good level of substrate-controlled diastereoselectivity (dr = 8 : 1, eqn (4)).…”

Photoinduced synthesis of functionalized oxetanes via diradical-mediated ring contraction

“…Ring contraction from a five- to a four-membered heterocycle is particularly attractive, because it converts one of the easiest-to-make ring sizes into one of the most difficult. 9 However, this approach is very challenging due to the increase of strain energy between the substrate and the product, which has limited the scope of methodologies that can be applied. The current successful validation of ring contraction strategy towards the synthesis of oxetanes has been reported by Fleet and co-workers, 10 whereas their protocols generally rely on the use of highly activated substrates, such as γ-lactones and other sugar derivatives (Scheme 1b).…”

Sequential Nucleophilic Arylation/Ring-Contractive Rearrangement of N-Alkoxylactams

“…To the best of our knowledge, there are no studies on the incorporation of C -nucleophiles in the aza-Favorskii rearrangement of α-halo lactams, even though the carbonyl group migrating in the reaction can serve as an effective proxy for a wide variety of other functional groups. Therefore, the C–C bond forming ring contraction of lactam remains a major synthetic challenge . Herein, we present the sequential nucleophilic arylation/ring contraction of δ-lactam for the synthesis of α-acylpyrrolidines …”