Mono-deoxygenation of Nitroalkanes, Nitrones, and HeterocyclicN-Oxides by Hexamethyldisilane through 1,2-Elimination:  Concept of “Counterattack Reagent”

Abstract

Transformation of secondary nitroalkanes to ketoximes was achieved in 40−73% yields by treatment of the corresponding nitronate anions with hexamethyldisilane. In this new mono-deoxygenation process, hexamethyldisilane acted as a “counterattack reagent”. The conversion of nitrones to imines was also achieved in 82−88% yields by use of trimethylsilyllithium. Similarly, heterocyclic N-oxides were converted to the corresponding N-heterocycles in 73−86% yields. These deoxygenation processes presumably involve a 1,2-elimination.

Ruthenium-Catalyzed Transfer Hydrogenation of Imines by Propan-2-ol in Benzene

“…Yield (3.6 g, 99 %) of white crystals. Spectral data were in accordance with those previously reported 19…”

Novel Penicillin-Type Analogues Bearing a Variable Substituted 2-Azetidinone Ring at Position 6: Synthesis and Biological Evaluation

“…The preparation of 2-azetidinones 5a – d (Scheme 2A) is performed by the Staudinger [2+2] cycloaddition reaction between properly substituted imines 3 and a ketene prepared in situ from methyl 3-(chloroformyl)propionate 4 [24,27,28]. The preparation of the imine precursor 3a – d was achieved in good yields (85%–96%) by condensation of the properly substituted aldehydes and anilines in ethanol [29,30,31,32]. The Staudinger reaction is one of the most widely employed methods in the preparation of β-lactam nucleus because it provides direct access to variously functionalized 2-azetidinones and allows to modulate the stereochemical outcome of the reaction.…”

“…Compounds 3a – d were prepared according to the previously described procedure and their spectral features matched with those reported in literature [29,30,31,32].…”

“…N-Benzylidene-3,4-dimethylbenzenamine ( 3b ). Recrystallized from ethanol as yellow solid [31]; m.p. 42–43 °C.…”

Recent synthetic developments in the nitro to carbonyl conversion (Nef reaction)

“…Various metal nitronates of secondary nitroalkanes 52 can be converted into the corresponding oximes 53 by treatment with hexamethyldisilane (Scheme 16). 42 According to the proposed mechanism, hexamethyldisilane acts as a 'counterattack reagent', towards nitronate anion 54 giving a silyl nitronate 55 as the first intermediate. The trimethylsilyl anion attacks the silyl nitronate 55 giving the adduct 56, that eliminates Me 3 SiO 2 providing the O-silylated oxime 57.…”