Curtius Rearrangement Reaction Research Articles

Identification of a Curtius Rearrangement Byproduct in LPA1 Antagonist (BMS-986020) Synthesis

BMS-986020 was developed as an antagonist of the LPA1 receptor for the treatment of lung fibrosis (Idiopathic Pulmonary Fibrosis (IPF)). During the development of BMS-986020, a high percentage byproduct was observed in the mother liquor of a Curtius rearrangement reaction. The structure identification and formation mechanism of this unknown byproduct was deemed necessary to understand for further the reaction optimization and knowledge generation for the project. The characterization process required a multifaceted approach utilizing LC-HRMS, VT-NMR, and HPLC isolation. The investigation’s final result implicated the reaction base as the root cause of the byproduct formation and indicated a nitrene-iminium reaction pathway to form the byproduct.

Design, synthesis and anticholinergic properties of novel α-benzyl dopamine, tyramine, and phenethylamine derivatives

Due to the important biological properties of dopamine, phenethylamine, and tyramine derivatives in the central nervous system, herein the synthesis of novel α-benzyl dopamine, phenethylamine, and tyramine derivatives is described. The title compounds were synthesized starting from 3-phenylpropanoic acids and methoxybenzenes in six or seven steps. Firstly, 3-(2,3-dimethoxyphenyl)propanoic acid (11) and 3-(3,4-dimethoxyphenyl)propanoic acid (12) were selectively brominated with N-bromosuccinimide (NBS). The Friedel–Crafts acylation of methoxylated benzenes with these brominated acids or commercially available 3-phenylpropanoic acid in polyphosphoric acid gave the desired dihydrochalcones. α-Carboxylation of dihydrochalcones, reduction of benzylic carbonyl groups, hydrolysis of esters to acid derivatives, and the Curtius rearrangement reaction of acids followed by in situ synthesis of carbamates from alkyl isocyanates and hydrogenolysis of the carbamates afforded the title compounds in good total yields. Alzheimer's disease (AD) and Parkinson's disease (PD) are chronic neurodegenerative diseases that become serious over time. However, the exact pathophysiology of both diseases has not been revealed yet. There have been many different approaches to the treatment of patients for many years, especially studies on the cholinergic system cover a wide area. Within the scope of this study, the inhibition effects of dopamine-derived carbamates and amine salts on the cholinergic enzymes AChE and BChE were examined. Dopamine-derived carbamate 24a-i showed inhibition in the micro-nanomolar range; compound 24d showed a Ki value of 26.79 nM against AChE and 3.33 nM against BChE, while another molecule, 24i, showed a Ki range of 27.24 nM and 0.92 nM against AChE and BChE, respectively. AChE and BChE were effectively inhibited by dopamine-derived amine salts 25j-s, with Ki values in the range of 17.70 to 468.57 µM and 0.76–211.23 µM, respectively. Additionally, 24c, 24e and 25m were determined to be 60, 276 and 90 times more selective against BChE than AChE, respectively.

Engineered Organic Nanorockets with Light-Driven Ultrafast Transportability for Antitumor Therapy.

Nanomedicines confront various complicated physiological barriers limiting the accumulation and deep penetration in the tumor microenvironment, which seriously restricts the efficacy of antitumor therapy. Self-propelled nanocarriers assembled with kinetic engines can translate external energy into orientated motion for tumor penetration. However, achieving a stable ultrafast permeability at the tumor site remains challenging. Here, sub-200nm photoactivated completely organic nanorockets (NRs), with asymmetric geometry conveniently assembled from photothermal semiconducting polymer payload and thermo-driven macromolecular propulsion through a straightforward nanoprecipitation process, are presented. The artificial NRs can be remotely manipulated by 808nm near-infrared light to trigger the photothermal conversion and Curtius rearrangement reaction within the particles for robustly pushing nitrogen out into the solution. Such a two-stage light-to-heat-to-chemical energy transition effectively powers the NRs for an ultrafast (≈300µm s-1 ) and chemical medium-independent self-propulsion in the liquid media. That endows the NRs with high permeability against physiological barriers in the tumor microenvironment to directionally deliver therapeutic agents to target lesions for elevating tumor accumulation, deep penetration, and cellular uptake, resulting in a significant enhancement of antitumor efficacy. This work will inspire the design of advanced kinetic systems for powering intelligent nanomachines in biomedical applications.

Do one‐step mechanisms always involve simultaneous evolution of electron density? QTAIM/IQA analysis of the Curtius rearrangement

AbstractThe Curtius rearrangement reaction is studied by using quantum theory of atoms in molecules (QTAIM) analysis of the electron density and the interacting quantum atoms (IQA) formalism. Although the rearrangements take place in one stage, two phases are distinguished when the rearranged atom is H: the first one corresponds to the separation of N2, and the second one to the N‐H/C‐H bond rearrangement. The transition state (TS) for the reaction does not represent an intermediate between reagent and product for the migration but for the isolation of the N2 molecule. When the migration is undergone by a fluorine atom, no electronic phases can be distinguished and the process is really concerted. As the migration happens closer to the TS, the TS is more similar to the product. The IQA analysis reveals different electron density evolutions for H and F migrations, and the scarce relevance (in terms of energy) of the point where BCPs appear or disappear.

Ureido Derivatives of Neoabietic Acid

A series of ureido derivatives of neoabietic acid were synthesized by application of Curtius rearrangement reaction to neoabietic acid and amines. Structure characterization of these compounds was done by 1H-NMR, 13C-NMR and HRMS spectral analysis.

Direct Observation of Carbamoylnitrenes.

As the prototype Curtius rearrangement reaction, carbamoyl azide decomposes into aminoisocyanate and molecular nitrogen. However, the key intermediate carbamoylnitrene was previously undetected, even though the decomposition of carbamoyl azides has been studied frequently since its discovery in the 1890s. Upon ArF laser (λ=193 nm) photolysis, the stepwise decomposition of the two simplest carbamoyl azides H2 NC(O)N3 and Me2 NC(O)N3, isolated in solid noble gas matrices, occurs with the formation of the corresponding carbamoylnitrenes H2 NC(O)N and Me2 NC(O)N. Both triplet species are characterized for the first time by combining matrix-isolation IR spectroscopy and quantum-chemical calculations. Subsequent visible-light irradiations cause efficient rearrangement of these nitrenes into the respective aminoisocyanates.

Synthesis and Characterization of Canola Oil-Based Polyisocyanates

In this study, canola oil triglycerides have been successfully transformed into canola oil-based polyisocyanates via thiol-ene click reaction and Curtius rearrangement reaction sequently. The synthesis method is non-phosgene and green. The structure of these novel diisocyanates was confirmed through Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (NMR). The result shows that the goal product has been produce successfully.

An efficient synthesis of carbon-14-labeled 6-[2-(dimethylamino)ethyl]-14-(1-ethylpropyl)-5,6,7,8-tetrahydroindolo [2,1-α] [2,5]benzodiazocine-11-carboxylic acid using Curtius rearrangement reaction as a key step

Here we report an efficient synthesis of 14C-labeled 6-[2-(dimethylamino)ethyl]-14-(1-ethylpropyl)-5,6,7,8-tetrahydroindolo-[2,1-α][2,5]benzodiazocine-11-carboxylic acid (1) using the Curtius rearrangement as a key step. The synthesis was initiated by converting the unlabeled aryl carboxylic acid to an aryl amine via Curtius rearrangement reaction. The resulting aryl amine was then converted to an aryl iodide which was coupled with zinc [14C]cyanide to form an aryl [14C]nitrile. Subsequent hydrolysis yielded the 14C-labeled carboxylic acid [14C]-1. This overall process represents a mild and potentially general approach for conversion of unlabeled carboxylic acids to isotopically labeled carboxylic acids. Copyright © 2010 John Wiley & Sons, Ltd.

Green and Highly Efficient Functionalization of Carbon Nanotubes by Combination of 1,3‐Dipolar Cycloaddition and Curtius Rearrangement Reactions

AbstractA facile and environmentally friendly strategy was developed for covalent modification of the convex surfaces of carbon nanotubes (CNT) through a combination of 1,3‐dipolar cycloaddition of azomethine ylides and Curtius rearrangement of carboxylic acid azides and its application in grafting polyamide 6 onto the surface of CNT was further investigated.

Azide monoliths as convenient flow reactors for efficient Curtius rearrangement reactions

The preparation and use of an azide-containing monolithic reactor is described for use in a flow chemistry device and in particular for conducting Curtius rearrangement reactions via acid chloride inputs.

A modular flow reactor for performing Curtius rearrangements as a continuous flow process

The use of a mesofluidic flow reactor is described for performing Curtius rearrangement reactions of carboxylic acids in the presence of diphenylphosphoryl azide and trapping of the intermediate isocyanates with various nucleophiles.

Traceless synthesis of quinazoline‐2,4‐diones by curtius rearrangement reaction using poly(ethylene glycol) as soluble polymeric support

Abstractmagnified imageWe have developed an efficient method to synthesize various quinazoline‐2,4‐diones using poly‐(ethylene glycol) as soluble polymeric support. The procedure of this reaction included: formation of acyl azide, efficient Curtius rearrangement, nucleophlic addition with amines to produce ureas, cyclization and concurrent cleavage of the resulted six‐membered heterocycle from PEG‐support in excellent yields. This method is mild and manipulation is easy.

Curtius rearrangement reactions of 3-(4-azidocarbonyl) phenylsydnone. Synthesis of 4-(sydnon-3-yl) phenyl carbamates, N-aryl-N′-[4-(sydnon-3-yl)] phenyl ureas and their antimicrobial and insecticidal activities

3-[4-(Azidocarbonyl)]phenylsydnone (2) obtained from 3-(4-hydrazinocarbonyl) phenylsydnone (1) on Curtius rearrangement with alcohols, water and amines afforded the corresponding carbamates (3a-h), 4,4′-(sydnone-3-yl) diphenyl urea (4) and 4-(heterocyclyl)phenyl ureas (5a-l). Compounds (5a-l) on one-pot ring conversion yielded the 1,3,4-oxadiazolin-2-one derivatives (6a-l), which on reaction with N2H4 gave the 4-amino-1,2,4-triazolin-3-ones (7a-l). All these compounds exhibited moderate antimicrobial activity against the few microbes tested. The carbamates have been found to be more toxic against fourth instar larvae ofAedes aegypti, in particular, then-butyl derivative (3e).

An alternative approach to aminodiols from Baylis-Hillman adducts: stereoselective synthesis of chloramphenicol, fluoramphenicol and thiamphenicol

We describe herein a new approach for the stereoselective synthesis of broad spectrum antibiotics from Baylis-Hillman adducts. The strategy is based on the preparation of an ene-carbamate directly from a Baylis-Hillman adduct using a Curtius rearrangement reaction. Stereoselective hydroboration furnished a mixture of diastereoisomeric aminoalcohols (syn and anti). After chromatographic separation, the syn diastereoisomer was directly transformed into the antibiotics.

Preparation and Applications of a Polymer‐Supported Phosphoryl Azide.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparation and applications of a polymer-supported phosphoryl azide

A polymer-supported diphenylphosphoryl azide was prepared. This polymer-supported version of DPPA is useful due to its lower toxicity, moisture tolerance and ease of workup after reaction. The synthetic application of this solid-phase reagent was explored by conversion of a variety of carboxylic acids to urethanes and ureas through Curtius rearrangement reactions. Carboxylic acids bearing different functional groups (aromatic, aliphatic and heterocyclic carboxylic acids) were subjected to the reaction. The corresponding products were isolated with satisfactory yields.

Synthesis of metal containing polyureas with a parabanic structure

A new diisocyanate containing a parabanic ring was synthesized via a Curtius rearrangement reaction. The direct reaction of this diisocyanate with the Mg salt of p-aminobenzoic acid, or with a mixture of aromatic diamines gave ionic polyureas with a parabanic structure. A detailed study of inherent viscosities of these polymers was achieved.

5312628 Isolation of a soluble 42 KD pancreatic islet cell autoantigen

A polymer-supported diphenylphosphoryl azide was prepared. This polymer-supported version of DPPA is useful due to its lower toxicity, moisture tolerance and ease of workup after reaction. The synthetic application of this solid-phase reagent was explored by conversion of a variety of carboxylic acids to urethanes and ureas through Curtius rearrangement reactions. Carboxylic acids bearing different functional groups (aromatic, aliphatic and heterocyclic carboxylic acids) were subjected to the reaction. The corresponding products were isolated with satisfactory yields.

Aliphatic-aromatic poly(ester-imide)s from diisocyanates containing ester groups and aromatic dianhydrides

Four new ester group containing diisocyanates, viz., 3,3′-(glutaryldioxy)diphenyl diisocyanate, 4,4′-(glutaryldioxy)diphenyl diisocyanate, 3,3′-(adipoyldioxy)diphenyl diisocyanate, and 4,4′-(adipoyldioxy)diphenyl diisocyanate were synthesized from the corresponding dicarboxylic acids via the Curtius rearrangement reaction. These diisocyanates were polycondensed with pyromellitic dianhydride (PMDA) and benzo-phenonetetracarboxylic dianhydride (BTDA) in dimethylacetamide to yield eight aliphatic-aromatic polyimides containing ester groups in the backbone with inherent viscosities in the range 0.25–0.70 dL/g. These poly(ester-imide)s were semicrystalline in nature and exhibited no weight loss below 300°C in air.

Synthesis and characterization of oxyethylene containing diisocyanates and polyimides therefrom

AbstractA facile synthesis of a series of oxyethylene containing diisocyanates, the α,ω‐bis(isocyanatophenoxy)alkanes and bis[2‐(isocyanatophenoxy)ethyl] ethers, is described. The key step involves the uneventful decomposition of the corresponding diacylazides to the diisocyanates in the Curtius rearrangement reaction. Further, eight thermally stable oxyethylene containing polyimides were synthesized by the polycondensation reaction of two meta‐ and two para‐oriented diisocyanates, namely, 1,2‐bis(3‐isocyanatophenoxy)ethane and 1,2‐bis(4‐isocyanatophenoxy)ethane, and bis[2‐(3‐isocyanatophenoxy)ethyl] ether and bis[2‐(4‐isocyanatophenoxy)ethyl] ether, with pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylic dianhydride (BTDA) in N,N‐dimethylacetamide (DMAc). These polyimides were characterized by IR spectroscopy, x‐ray diffraction, viscosity measurements, and thermogravimetric analysis.