α‐Electrophilic Reactivity of Nitronates

Abstract

Chemistry of covalent nitronates regarding nucleophilic addition to C=N bond is described. Various types of electrophilic activation of nitronates and stability of formed products are discussed with main attention paid to authors' work in the area.

In Situ Generated Magnesium Cyanide as an Efficient Reagent for Nucleophilic Cyanation of Nitrosoalkenes and Parent Nitronates

“…We have demonstrated that under certain activation conditions (treatment with strong silicon‐centered Lewis acids) nitronates 1 can serve as α‐ and β‐electrophilic reagents. [10a], In particular, recently we reported a TBSOTf‐promoted addition of TBSCN to cyclic O ‐alkyl nitronates Alk ‐ 1 affording the corresponding α‐cyano‐substituted nitroso acetals 2 (Scheme ) . Also, we developed β‐cyanation of O ‐silyl nitronates Si ‐ 1 through their transformation to N , N ‐bis(silyloxy)enamines 4 and addition of TMSCN via the intermediacy of nitrosoalkenes NSA (Scheme ) .…”

Tandem Deoxygenation/Halogenation of N‐Oxides Under Acylation Conditions: Scope and In Situ IR Spectroscopic Study

“…Chemical modifications of N ‐oxides of type 1 are usually performed via three major routes (Scheme ): (a) TMSOTf‐mediated nucleophilic addition to C=N bond; (b) [3+2]‐dipolar cycloaddition;[1a], [1d] (c) transformation into N ‐siloxyenamines followed by Lewis acid‐mediated S N ′‐substitution of TMSO‐group . Recently, we reported a novel functionalization of nitronates 1 exploiting tandem acylation/[3,3]‐sigmatropic rearrangement process upon the action of R 1 COCl with Et 3 N (Scheme ) .…”

C−H Reactivity of the α‐Position in Nitrones and Nitronates

“…Enamines 13 react smoothly with acetals and ketals in the presence of 1 equivalent of trimethylsilyl triflate to give γ‐alkoxy‐substituted nitro compounds 61 in high yields (Scheme ) . Since both N , N ‐bis(siloxy)enamines 13 and the initially formed silyl nitronates 63 are unstable to Lewis acids, the coupling is performed at −78 °C. The reaction is restricted to N , N ‐bis(siloxy)enamines 13 derived from secondary nitro compounds.…”

“…Sixty years after this statement was made, we would like to summarize the state‐of‐art in the chemistry of azomethine N ‐oxides 1 involving reactions at their α‐carbon atom together with examples of the utility of these reactions in target‐oriented organic synthesis. Although some specific reactions of this type have been mentioned in previous reviews on the chemistry of nitrones and nitronates, the present paper is the first attempt to systemize these processes and consider azomethine N ‐oxides 1 as α‐CH‐active substrates that are similar and at the same time different from carbonyl compounds.…”