title: Synthesis of enantiopure indolizinones by cascade ring enlargements of 4'-chlorospiro[cyclopropane-1,5'-isoxazolidines].
abstract: 2-Chloro-2-cyclopropylideneacetates (1-Me and 1-Et) and their spiropentane analogues 2 cycloadd enantiopure five-membered cyclic nitrones to give the corresponding adducts (quantitatively, four examples), which undergo cascade ring enlargements to yield indolizinone derivatives (53-70%, four examples). The ring enlargement process is triggered by the abstraction of a bridgehead proton induced by a base and can be suppressed by the presence of a bulky substituent nearby, such as a (triisopropylsilyl)oxy group.
authors.affiliation: Dipartimento di Chimica Organica U. Schiff, Università di Firenze, Via della Lastruccia, 13, I-50019 Sesto Fiorentino, Firenze, Italy.
authors.forename: Julia
authors.initials: J
authors.lastname: Revuelta
authors.forename: Stefano
authors.initials: S
authors.lastname: Cicchi
authors.forename: Cristina
authors.initials: C
authors.lastname: Faggi
authors.forename: Sergei I
authors.initials: SI
authors.lastname: Kozhushkov
authors.forename: Armin
authors.initials: A
authors.lastname: de Meijere
authors.forename: Alberto
authors.initials: A
authors.lastname: Brandi
mesh_terms: D003500:Cyclization; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry; D007555:Isoxazoles / Q000737:chemistry*; D008968:Molecular Conformation; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D007212:Indolizines; D007555:Isoxazoles; D013141:Spiro Compounds