A General Metal‐Assisted Synthesis of α‐Halo Oxime Ethers from Nitronates and Nitro Compounds

Abstract

An approach to the synthesis of α‐halo oxime ethers from readily accessible nitronates and nitro compounds via bis(oxy)enamines is reported. A key step of the strategy involves the unprecedented reaction of bis(oxy)enamines with a metal (Co, Zn, Mg, Mn) halide that acts as both a promoter and halide (Br, I, Cl) source. A variety of cyclic and acyclic ethers of α‐halo oximes, including previously unavailable trimethylsilyl ethers of α‐iodo oximes, have been synthesized in good‐to‐high yields.

Divergent Reactivity of In Situ Generated Metal Azides: Reaction with N,N‐Bis(oxy)enamines as a Case Study

“…Based on our prior studies on reactions of bis(oxy)enamines 2 with metal halides, we speculated, that the presence of Lewis acidic metal cations may direct the attack of the azide anion on the C,C double bond by activating the cleavage of the weak exocyclic N−O bond. Since most of metal azides are not available in a free state, we attempted to generate these species in situ by the ion exchange between NaN 3 and the corresponding metal salt containing a non‐nucleophilic counterion (triflate or perchlorate).…”

“…These electrophilic reagents are easily accessible by silylation of aliphatic nitro compounds or readily available cyclic nitronates . Owing to the pyramidality of nitrogen and strong π→σ * N−O , n O →σ * N−O interactions, bis(oxy)enamines 1 and 2 can enter S N ′ reactions at the β‐carbon atom with the breakage of one of two weak nitrogen−oxygen bonds (Scheme ) ,. Another electrophilic center in their structure is silicon atom.…”

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

“…Thus, the reaction of N , N ‐bis(oxy)enamines 13 and 15 with cobalt(II) halides results in the formation of α‐halo‐substituted oxime ethers [Scheme , Eqs. (1) and (2)] . In a similar fashion, the nitrate anion, in the form of chromium or cobalt nitrate, can be used as a nucleophile [Scheme , Eq.…”