Über Alkylenimin‐Derivate. 6. Mitteilung. Über die partielle Reduktion von cyclischen Imiden

Abstract

It is shown that LiAIH4 reduces cyclic imides, namely 3,3‐disubstituted 2,5‐dioxo‐pyrrolidines and 2,6‐dioxo‐piperidines, primarily at the oxo‐group not adjacent to the two substituents. Hydroxylactames are formed as the first reduction products. Similarly, the same oxygen atom is replaced by sulfur by reaction with P2S5. This behaviour is ascribed to steric hindrance.

Regioselective Reduction of 3-Sulfonyl Glutarimides to 3,4-Dihydro-5-sulfonylpyridin-2-ones. Formal Synthesis of the Indolizidine 8a-epi-Dendroprimine

“…Regioselective reduction of cyclic imides has attracted considerable interest among organic chemists, − partly because the resulting hydroxylactams can be converted to corresponding N -acyliminium intermediates and then further transformed into different alkaloids, such as indolizidines, quinolizidines, isoquinolines, and indoles , In this report, we describe a general method which regioselectively reduces the carbonyl group on 3-sulfonyl glutarimides 1 and leads to corresponding hydroxylactams 2 , which are then further converted to 3,4-dihydro-5-sulfonylpyridin-2-ones 3 . Formal synthesis of 8a- epi -dendroprimine ( 4 ) via intramolecular radical cyclization of cyclic vinyl sulfone 5 is also reported.…”

Synthesis by Reduction

“…[231,232] Other borohydride reducing agents, such as tetramethylammonium triacetoxyborohydride [233] or lithium tri-secbutylborohydride (L-Selectride), [233] can also be used for this transformation. Even very strong reducing agents, such as diisobutylaluminum hydride, [234] sodium bis(2-methoxyethoxy)aluminum hydride (Red-Al), [233] or lithium aluminum hydride, [233,235,236] can form N-acylated hemiaminals from imides when used under mild reaction conditions with controlled stoichiometry. To obtain amides from imides, the remaining hydroxy or alkoxy moiety of the resulting hemiaminals or O,N-acetals can be reductively removed with a reducing agent such as diisobutylaluminum hydride, sodium bis(2-methoxyethoxy)aluminum hydride, or 9-borabicyclononane.…”

Intramolecular Reversible Addition Reactions to the C=O Group

“…3-(2-Phenyl-I,3-indanedione-2-yl)propionamides also exist only in an open form [68,195,198]. Some 4-formylbutyramides [244] and their chain substituted derivatives [327,328] possess a cyclic structure, probably due to an increased electrophilicity of the formyl group as compared with the keto group.…”