Iminoxyl Radical-Promoted Dichotomous Cyclizations: Efficient Oxyoximation and Aminooximation of Alkenes

Abstract

A novel iminoxyl radical-involved metal-free approach to vicinal oxyoximation and aminooximation of unactivated alkenes is developed. This method utilizes the dichotomous reactivity of the iminoxyl radical to furnish a general difunctionalization on alkenes using simple tert-butyl nitrite (TBN) as the iminoxyl radical initiator as well the carbon radical trap. By using this protocol, oxime featured 4,5-dihydroisoxazoles and cyclic nitrones were facilely prepared from β,γ- and γ,δ-unsaturated ketoximes, respectively.

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

“…Owing to the unpaired electron density -3 -on both the O and N atoms, these iminoxyls were utilized in double-heteroatom-containing cyclizations leading to differently functionalized isoxazolines and cyclic nitrones regarded as important reagents for pharmacology. 8,9 The angular structure of the C=N-O• moiety, theoretically confirmed for various R 1 R 2 C=N-O• radicals by our DFT calculations [10][11][12][13][14][15] , provides an exceptional ability of the iminoxyls with two different substituents at azomethine carbon (R 1 ≠ R 2 ) to exist as two isomers, E and Z, with the possibility of interconversion. It is characteristic that when one of the substituents is a phenyl ring its rotation is manifested in the EPR spectrum.…”

tert‐Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis

“…Heterocycles containing substrates were transformed into their desired products in excellent yields. The cyclic nitrone carbaldehyde oximes were obtained in good to moderate yields from unsaturated ketoxime with terminal olefins (Scheme ) …”

“…The cyclic nitrone carbaldehyde oximes were obtained in good to moderate yields from unsaturated ketoxime with terminal olefins (Scheme 89). [118] In 2009, Beller group reported aF e-catalyzed synthesis of oximes (122)f rom olefins (121)i nt he presence of sodium borohydride. Electron-richo lefins provided higher yields as compared to electron-withdrawing olefins.…”

Recent Advances in Highly Selective Applications of Nitroso Compounds

“…By using tBuONO as an iminoxyl radicali nitiator and ac arbon-radical trap, Han and co-workersd eveloped an iminoxyl-radical-involved metal-free approachf or the vicinal oxyoximation and aminooximation of inactivated alkenes (67); oximes that featured 4,5-dihydroisoxazoles andc yclic nitrones were facilely prepared from the intramolecular cyclization of b-, g-, and g,d-unsaturated ketoximes (68-70;Scheme 26). [46] 6. Nitroso Group as aDirecting Group in CÀH Activation Reactions Catalytic CÀHf unctionalization is av alued and step-economical strategy for the elaboration of organic molecules.…”