Annulation of unsaturated silyl nitronates

Enantiosective synthesis of a substituted cyclopentanone with all-carbon quaternary stereocenter

“…ref. 23). In this case it gives a mixture of isomeric oximes 7a,b (anti-/syn-≈ 12 : 1, 1 H NMR data) through initial formation of plausible nitroso intermediate 6.…”

“…refs. [22][23][24][25]. Further transformation of cyclopentaisoxazolidine 5 consisted in isoxazolidine fragment opening upon the action of sodium methoxide as described earlier for related compounds (cf.…”

“…We surmised that the advantages of this approach could additionally be shown using an annulation reaction by intramolecular dipolar [3+2] cycloaddition of silyl nitronates generated from chiral unsaturated nitro compounds. Previously we have demonstrated 22,23 a strong stereocontrol of the formation of substituted cyclopentane and cyclohexane rings in such cycloadditions directed by a substituent on the corresponding nitronate derived from the starting nitroolefin (cf. refs 24,25) (Scheme 1).…”