A simple method for the preparation of medium ring heterocycles (7-, 8-, 9-, and 10-membered) has been developed. The process employs a Cu-catalyzed coupling of a beta-lactam with an aryl bromide or iodide followed by intramolecular attack of a pendant amino group. In some instances, the intermediate beta-lactam is observable but can be converted to the aza-heterocycle by catalysis. Acetic acid was found to be superior to transition metal complexes as a catalyst for this ring-expansion process.

Versatile synthetic intermediates were formed by the dearomatization of 2‐aryl 4,5‐diphenyloxazolines with secondary alkyl lithium reagents in the presence of N,N′‐dimethylpropyleneurea (DMPU; see scheme). The resulting cyclohexadiene derivatives were converted into carbocyclic analogues of mannose and altrose in a short sequence without the use of protecting groups.

No abstract

Versatile synthetic intermediates were formed by the dearomatization of 2‐aryl 4,5‐diphenyloxazolines with secondary alkyl lithium reagents in the presence of N,N′‐dimethylpropyleneurea (DMPU; see scheme). The resulting cyclohexadiene derivatives were converted into carbocyclic analogues of mannose and altrose in a short sequence without the use of protecting groups.

No abstract