Untersuchungen an Diazoverbindungen und Aziden, LII. Stabile Azomethinimin‐Dipole aus Diazoverbindungen und 3
            <i>H</i>
            ‐1,2,4‐Triazol‐3,5(4
            <i>H</i>
            )‐dionen

Theis, Wolfgang; Bethäuser, Willi; Regitz, Manfred

doi:10.1002/cber.19851180105

Cited by 18 publications

(3 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Combining the insights gained from DFT calculations ( Figure 2) with conclusions from pioneering work on the generation of N-isocyanates from the literature, [16] efforts were initiated towards an improved aminocarbonylation process. These targeted new aminocarbonylation precursors, and the study of their reactivity under thermolytic conditions, to identify milder aminocarbonylation conditions.…”

Section: Resultsmentioning

confidence: 99%

Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino‐Isocyanates

Ivanovich

Clavette

Vincent-Rocan

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

The ubiquity of nitrogen heterocycles in biologically active molecules challenges synthetic chemists to develop a variety of tools for their construction. While developing metal-free hydroamination reactions of hydrazine derivatives, it was discovered that carbazates and semicarbazides can also lead to alkene aminocarbonylation products if nitrogen-substituted isocyanates (N-isocyanates) are formed in situ as reactive intermediates. At first this reaction required high temperatures (150-200 °C), and issues included competing hydroamination and N-isocyanate dimerization pathways. Herein, improved conditions for concerted intramolecular alkene aminocarbonylation with N-isocyanates are reported. The use of βN-benzyl carbazate precursors allows the effective minimization of N-isocyanate dimerization. Diminished dimerization leads to higher yields of alkene aminocarbonylation products, to reactivity at lower temperatures, and to an improved scope for a reaction sequence involving alkene aminocarbonylation followed by 1,2-migration of the benzyl group. Furthermore, fine-tuning of the blocking (masking) group on the N-isocyanate precursor, and reaction conditions relying on base catalysis for N-isocyanate formation from simpler precursors resulted in room temperature reactivity, consequently minimizing the competing hydroamination pathway. Collectively, this work highlights that controlled reactivity of aminoisocyanates is possible, and provides a broadly applicable alkene aminocarbonylation approach to heterocycles possessing the β-aminocarbonyl motif.

show abstract

Section: Resultsmentioning

confidence: 99%

Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino‐Isocyanates

Ivanovich

Clavette

Vincent-Rocan

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…A similar cycloreversion approach to form iminoisocyanates was reported by Regitz in 1985 (Equation 4). 23 In this case, triazoline-3,5-diones were allowed to react with diazo compounds at room temperature. Subsequent loss of nitrogen gas generated the azomethine imine.…”

Section: Scheme 12 the First Report Of The Formation Of Iminoisocyanatesmentioning

confidence: 99%

N-Isocyanates, N-Isothiocyanates and Their Masked/Blocked Derivatives: Synthesis and Reactivity

Vincent-Rocan

Beauchemin

2016

Synthesis

View full text Add to dashboard Cite

In contrast to C-substituted isocyanates which are frequently used reagents in synthesis, nitrogen-substituted isocyanates (N-isocyanates) remained a scientific curiosity in the literature for over a century. The amphoteric character of these reactive intermediates, which results in their propensity to dimerize, prevented the development of their full synthetic potential. In this review, the pioneering work that led to the development of reliable methods for their synthesis, established the existence of such species by spectroscopy, and allowed a delineation of their basic reactivity is presented. The high reactivity of these intermediates has been controlled through the use of masked precursors to regulate their concentration via a reversible equilibrium, a strategy which is also used in industrial processes utilizing C-isocyanates. This control led to the development of more complex reactions, including reaction cascades that allow the rapid synthesis of heterocycles possessing the N-N-C=O motif, which is widely present in agrochemicals and pharmaceuticals. This review covers the literature of N-isocyanates and their sulfur analogues, N-isothiocyanates, until April 2016. 1 Introduction 2 Formation of N-Isocyanates 2.1 Rearrangement of Carbamoyl Azides 2.2 Ring Opening of Heterocycles 2.3 Thermolysis of Hydrazine Derivatives 3 Formation of N-Isothiocyanates 4 Isolation and Observation 4.1 Isolation and Observation of N-Isothiocyanates 4.2 Isolation and Observation of N-Isocyanates 5 Reactivity 5.1 Reactivity of N-Isothiocyanates 5.2 Reactivity of N-Isocyanates 6 Conclusion Key words isocyanatoamines, isocyanatoimines, nitrogen-substituted isocyanates, heterocyclic chemistry, cascade reactions, amphoteric reagents synthesis of: pharmaceuticals agrochemicals polyurethanes

show abstract

“…[22] In order to furnish chemical proof for betaines 10, we tried to trap them by [32] cycloaddition reaction with a suitable dipolarophile. In fact, this transformation was successful with dimethyl acetylenedicarboxylate (DMAD), but not with methyl propiolate, dimethyl fumarate, dimethyl maleate, maleic anhydride, or norbornadiene.…”

Section: Introductionmentioning

confidence: 99%

Photochemical Isomerizations of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines): (5→4) Ring Contraction Generates Azomethineimine Dipoles

1998

View full text Add to dashboard Cite

UV irradiation of the title compounds 1 a ± d results not in extrusion of molecular nitrogen, but in a skeletal rearrangement generating amino(imidoyl)-phosphanes 2 a ± c from 1 a ± c and 2-hydrazinobenzo[b]phosphole 4 from 1 d. The first step in these isomerizations is an unprecedented (5 34) ring contraction of 1 to form the semicyclic azomethineimine dipoles 10 incorporating a 1,2,3-diazaphosphetidine ring. Dipoles 10 a ± c, but not 10 d, can be observed by NMR spectroscopy after brief irradiation of the precursors. Furthermore, they could be trapped by [32] cycloaddition reaction with dimethyl acetylenedicarboxylate to give the bicyclic 1,2,3-diazaphosphetidines 12 a ± c, and, in the case of 10 a and 10 c, also the dihydrophospholes 13 a,c resulting from a second [32] cycloaddition.

show abstract

Untersuchungen an Diazoverbindungen und Aziden, LII. Stabile Azomethinimin‐Dipole aus Diazoverbindungen und 3 H ‐1,2,4‐Triazol‐3,5(4 H )‐dionen

Cited by 18 publications

References 18 publications

Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino‐Isocyanates

Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino‐Isocyanates

N-Isocyanates, N-Isothiocyanates and Their Masked/Blocked Derivatives: Synthesis and Reactivity

Photochemical Isomerizations of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines): (5→4) Ring Contraction Generates Azomethineimine Dipoles

Contact Info

Product

Resources

About