Synthesis of enantiopure indolizinones by cascade ring enlargements of 4'-chlorospiro[cyclopropane-1,5'-isoxazolidines].
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.
Revuelta
Julia
J
Dipartimento di Chimica Organica U. Schiff, Università di Firenze, Via della Lastruccia, 13, I-50019 Sesto Fiorentino, Firenze, Italy.
Cicchi
Stefano
S
Faggi
Cristina
C
Kozhushkov
Sergei I
SI
de Meijere
Armin
A
Brandi
Alberto
A
D003500:Cyclization; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry; D007555:Isoxazoles / Q000737:chemistry*; D008968:Molecular Conformation; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D007212:Indolizines; D007555:Isoxazoles; D013141:Spiro Compounds