Facile construction of small and normal-sized, or more precisely, four to seven-membered aza-heterocyclic ring systems is always a challenging yet rewarding task for the synthetic organic chemists. Fortunately, activated aziridines and azetidines provide a direct and convenient access to this coveted molecular architectures through several elegant ring-expansion approaches. This chapter presents some of the illustrative and contemporary examples to demonstrate the synthetic diversity and efficiency of the ring-expansion strategies of activated aziridines and azetidines towards a vast array of small to normal-sized aza-heterocyclic moieties.
This review summarises the remarkable advancements in the ring-opening chemistry of donor–acceptor cyclopropanes (DACs) using C-nucleophiles to construct varieties of carbocycles.
A simple synthetic route to access
racemic 3,3-disubstituted propylamines
in excellent yields (up to 95%) via Lewis acid catalyzed SN2-type ring opening of activated azetidines with electron-rich arenes
and heteroarenes under mild conditions has been accomplished. The
methodology is efficiently used for the racemic synthesis of an antimuscarinic
drug, tolterodine, in four steps in 47% overall yield.
A simple and efficient synthetic route to substituted N-sulfinyl and N-sulfonyl azetidines is described involving imino-aldol reaction of ester enolates with racemic and non-racemic aldimines for obtaining β-amino esters as a key step. These β-amino esters on subsequent reduction followed by TsCl/KOH mediated cyclization produced the corresponding racemic and non-racemic azetidines with high yield and stereoselectivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.