Exploring the nucleophilicity of N,N′‐diamidocarbenes: Heteroallenes and related compounds as coupling reagents

Abstract

The propensity of a stable N,N′‐diamidocarbene (DAC) to react with various heteroallenes was explored. The DAC condensed with 4‐nitrophenyl azide as well as 4‐nitrophenyl isothiocyanate to afford the respective acyclic triazene or zwitterionic dihydropyrimidinium imidothiolate products. Treating the DAC with two equivalents of 3‐nitrophenyl isocyanate afforded an iminooxazolidinone rather than the expected hydantoin. Similarly, the addition of diphenylketene to the DAC afforded a dioxolane product, whereas analogous reactions involving N‐heterocyclic carbenes (NHCs) resulted in betaine adducts. Although the DAC as well as various diaminocarbenes condensed with 2,6‐dimethoxyphenyl nitrile N‐oxide to afford the respective nitrosoethylenes, only the six‐membered DAC and NHC adducts rearranged to the corresponding nitrones at elevated temperature. Copyright © 2012 John Wiley & Sons, Ltd.

The Ambivalent Chemistry of a Free Anionic N‐Heterocyclic Carbene Decorated with a Malonate Backbone: The Plus of a Negative Charge

“…Further loss of molecular nitrogen from the triazene intermediate generally occurs under heating or acidic conditions to afford cyclic guanidines or guanidinium salts 40. 41 This reaction thus appears as a valuable strategy for the introduction of a nitrogen atom onto a carbenic center (formally as a nitrene moiety), but, to the best of our knowledge, it has been applied mainly to 5‐membered (benz)imidazol(in)‐2‐ylidenes, and to the notable case of the diamidocarbene A 42. In our experiment, the reaction of [ 1 ] ⋅ Li with benzyl azide was found to be complete within less than one hour, giving an anionic triazene intermediate that was decomposed in situ by the addition of a small excess of hydrogen chloride, to give compound 11 , which is globally neutral and was easily isolated in 78 % yield after purification by flash chromatography.…”

“…[40,41] This reaction thus appears as a valuable strategy for the introduction of a nitrogen atom onto a carbenic center (formally as a nitrene moiety), but, to the best of our knowledge, it has been applied mainly to 5-membered (benz)imidazol(in)-2ylidenes, and to the notable case of the diamidocarbene A. [42] In our experiment, the reaction of [1]·Li with benzyl azide was found to be complete within less than one hour, giving an anionic triazene intermediate that was decomposed in situ by the addition of a small excess of hydrogen chloride, to give compound 11, which is globally neutral and was easily isolated in 78 % yield after purification by flash chromatography. The presence of a signal at d = 4.82 ppm integrating for two protons in the 1 H NMR spectrum is in agreement with the presence of two hydrogen atoms on the exocyclic nitrogen.…”

A theoretical study on the hydrogen adducts of diamidocarbenes and diaminocarbenes

“…(4) The ability of the hydrogen adduct 4H to store hydrogen is also enhanced with the substitution of electrondonating groups on N 2 and N 5 . [36][37][38][39]. For example, Lee et al [36] discovered that N,N′-diamidocarbenes are ambiphilic and can behave as electrophiles and nucleophiles.…”

“…[36][37][38][39]. For example, Lee et al [36] discovered that N,N′-diamidocarbenes are ambiphilic and can behave as electrophiles and nucleophiles. We believe that our results can provide a basis for rationalizing more appropriately the effect of the insertion of an oxalamide into the heterocyclic ring of an NHC.…”

Poly(2-imino-4-oxazolidinone)s via the Condensation of Diamidocarbenes with Bis(isocyanate)s

“…The structure of this product was unambiguously elucidated using single crystal X-ray diffraction (XRD) analysis (Figure 1, left), which confirmed the formation of the oxazolidinone heterocycle 2, rather than the isomeric hydantoin 3. 16 We postulated that the formation of 2 originated from the generation of a carbimidate intermediate, 1′. To test this hypothesis, one equivalent of phenylisocyanate was combined with 1 in C 6 H 6 , which resulted in the nearly instantaneous formation of a purple solution.…”