Synthesis of Fused Piperidinones through a Radical-Ionic Cascade
Edouard Godineau
Kurt Schenk
Yannick Landais
10.1021/jo801308j.s001
https://acs.figshare.com/articles/journal_contribution/Synthesis_of_Fused_Piperidinones_through_a_Radical_Ionic_Cascade/2912884
Azabicyclo[4.3.0]nonanes were assembled, from chiral allylsilanes possessing an oxime moiety, using a stereocontrolled formal [2 + 2 + 2] radical-ionic process. The cascade involves the addition of an α-iodoester to the less substituted end of the enoxime which is then followed by a 5-<i>exo</i>-<i>trig</i> cyclization onto the aldoxime function, producing an alkoxyaminyl radical species which finally lactamizes to afford the titled piperidinone. High levels of stereoinduction were observed, demonstrating the ability of a silicon group located at the allylic position to efficiently control the stereochemistry of the two newly created stereogenic centers. When the radical cascade was extended to ketoximes, the resulting sterically hindered alkoxyaminyl radical did not react further with the initiator Et<sub>3</sub>B to produce the expected nucleophilic amidoborane complex. In sharp contrast, this long-lived radical recombined with the initial α-stabilized ester radical to produce a cyclopentane incorporating two ester fragments.
2008-09-19 00:00:00
lactamize
aldoxime function
ketoxime
enoxime
chiral allylsilanes
High levels
nucleophilic amidoborane
initiator Et 3B
species
cyclopentane
cyclization
recombined
stereochemistry
Azabicyclo
stereoinduction
Synthesi
ester fragments
ability
Fused Piperidinones
iodoester
Cascade
stereocontrolled
silicon group
oxime moiety
sterically
stereogenic centers
piperidinone
cascade
allylic position
contrast
alkoxyaminyl