256ChemInform Abstract Treatment of lactones (I) with tBuOK results either in abstraction of a proton to give (II) or in the formation of the "living polymers" (III) and subsequent cyclization/degradation to provide the title compounds (IV). Thus, (Ia) is transformed to the 14-to 28-membered heterocycles (IVa)-(IVc) whereas (Ib), under similar conditions but with higher concentrations of the catalyst, yields the salt of (IIb). On addition of tBuOH, however, the hitherto unknown macrocycles (IVd)-(IVf) are obtained from (Ib), probably because the formation of (IV) from a larger number of shorter polymers (III) can now compete with the more favoured degradation to the starting lactone. Even with greater amounts of catalyst, (Ic) only gives aldol type condensation products (V) and (VI) (from (IIc)), while the veryreactive 4-membered lactone (Id) produces acrylic acid and higher homologues (VIII) (via ring-opening of (IId)). The latter substrate is the only lactone studied that can be converted to the target compounds (i.e. (IVg)-(IVi)) by addition of an electrophilic catalyst (BF3, TiCl4 or H2SO4). (Some yields not given).
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.