In situ NMP

Nesvadba and coworkers [270] used nitrones in controlled radical polymerization of vinyl monomers. This was the beginning of the in situ NMP concept. The alkoxyamines were prepared... 

Subsequently, nitroxides and parent alkoxyamines were formed directly in the polymerization medium (in situ NMP) by reaction of the nitrone with the free radical initiators [270]. Two types of reactions were carried out. One was a reaction before monomer addition and the other one after the addition. In either case, a prereaction was systematically carried out at temperatures ranging from 60 to 80°C. This was followed by polymerizations at 130°C. The in situ-formed nitroxides and alkoxyamines controlled the radical polymerizations of n-butyl acrylate yielding, however, low molecular weight polymers, of < 10,000 and equal to 1.65-2.0. 

Describe nitroxyl radical mediated polymerizations. Illustrate TEMPO controlled polymerization of styrene. What is meant by in situ NMP ... 

Zarycz N, Botek E, Champagne B, SciannameaV, Jerome C, Detrembleur C. Joint theoretical experimental investigation of the electron spin resonance spectra of nitroxyl radicals application to intermediates in in situ nitroxide mediated polymerization (in situ NMP) of vinyl monomers. J Phys Chem B 2008 112 10432-10442. 

Many authors and in particular Jerome and Detrembleui developed the in situ NMP process by adding to a conventional radical polym erization mixture various nitroxide precursors such as sodium nitiite/nitric oxide, nitroso compormds, nitrones, amines, ° and hydroxylamines. ° In aU cases, quite successful controlled/living polymerizations were obtained even if the nature of the control agent is difficult to identify. 

This approach attracted considerable interest due to its potential for industrial applications because the nitroxide precursors are inexpensive. However, these systems are much more complex than those using a pure unimolecular initiator, and the underlying mechanisms must be well understood before the systems can be optimized and applied industrially. The state of the art of so-called in-situ NMP as of 2008 was reviewed by Detrembleur et al ... 

Recently, a new variant of in-situ NMP was reported by Barner-Kowollik et u/. First, a macromolecular mid-chain alkoxyamine 21 is obtained via addition of two macroradicals to a nitrone, e.g. phenyl-t-butyl nitrone 20... 

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

A number of NMP processes have been reported where the nitroxide is formed in situ. Nitrones 1 and nitroso-compounds128 have been used as nitroxide precursors. Control of methacrylate polymerization by mixtures of nitric oxide and nitrogen dioxide has also been attributed to in situ formation of a nitroxide. 130... 

Catala and coworkers167JuiS made the discovery that the rate of TEMPO-mediated polymerization of S is independent of the concentration of the alkoxyamine. This initially surprising result was soon confirmed by others.23 69 Gretza and Matyjaszewski169 showed that the rate of NMP is controlled by the rate of thermal initiation. With faster decomposing alkoxyamines (those based on the open-chain nitroxides) at lower polymerization temperatures, the rate of thermal initiation is lower such that the rate of polymerization becomes dependent on the alkoxyamine concentration, Irrespective of whether the alkoxyamine initiator is preformed or formed in situ, low dispersities require that the alkoxyamine initiator should have a short lifetime. The rate of initiation should be as fast as or faster than propagation under the polymerization conditions and lifetimes of the alkoxyamine initiators should be as short as or shorter than individual polymeric alkoxyamines. 

Functional alkoxyamines used as initiators for NMP include 283-287. The functional alkoxyamines can be formed in situ by use of a functional azo compound or peroxide. NMP has been shown to be compatible with hydroxy, epoxy, amide and tertiary amine groups in the initiator. Carboxylic acid groups can cause problems but may be tolerated in some circumstances.106... 

Low-valent lanthanides represented by Sm(II) compounds induce one-electron reduction. Recycling of the Sm(II) species is first performed by electrochemical reduction of the Sm(III) species [32], In one-component cell electrolysis, the use of sacrificial anodes of Mg or A1 allows the samarium-catalyzed pinacol coupling. Samarium alkoxides are involved in the transmet-allation reaction of Sm(III)/Mg(II), liberating the Sm(III) species followed by further electrochemical reduction to re-enter the catalytic cycle. The Mg(II) ion is formed in situ by anodic oxidation. SmCl3 can be used in DMF or NMP as a catalyst precursor without the preparation of air- and water-sensitive Sm(II) derivatives such as Sml2 or Cp2Sm. 

Knochel demonstrated the effectiveness of soluble potassium or cesium alkoxides such as KO Bu or CsO Bu as well as KH in iV-methylpyrrolidinone (NMP) for promoting the 5-endo-dig cyclizations of 2-alkynylanilines to 2-substituted indoles in solution or the solid-phase <00AG(E)2488>. Alternatively, Cacchi coupled a palladium-catalyzed cyclization of o-alkynyltrifluoroacetanilides with the addition of benzyl bromide or ethyl iodoacetate to afford 2-substituted-3-benzyl or 3-indolylcarboxylate esters, respectively <00SL394>. Yamamoto reported a new palladium catalyzed indole synthesis in which 2-(l-alkynyl)-Ar-alkylideneanilines 117 give 2-substituted-3-(l-alkenyl)indoles 118 directly from the imine by the in situ coupling of an aldehyde with the alkynylaniline <00JA5662>. 

Sciannamea, V. Jerome, R. Detrembleur, C. In-situ nitroxide-mediated radical polymerization (NMP) processes Their understanding and optimization. Chem. Rev. 2008,108, 1104-1126. 

It was also reported that these reactions proceed equally well in pure THF when two equivalents of LiBr are added13. Alternatively, the diorganozinc can be prepared reacting ZnBr2 with two equivalents of RLi or RMgBr, thus producing LiBr or MgBr2, respectively in situ. Obviously, LiBr and polar cosolvents such as NMP increase the reactivity of intermediates like 2515,1 . 

However, nucleoside diphosphates (NDP) are still expensive substrates, which can be obtained from much more cheaper nucleoside monophosphates (NMP). In this respect we have combined the SuSy-catalyzed cleavage of sucrose with the enzymatic formation of NDPs from NMPs catalyzed by nucleoside monophosphate kinase (NMPK, EC 2.7.4.4) or myokinase (MK, EC 2.7.4.3), including in situ regeneration of ATP with pyruvate kinase (PK, EC 2.7.1.40) (Fig. 20) [272]. Testing the substrate spectrum of four different kinases disclosed that none of them accepted dTMP as substrate [272], However, dUMP was well accepted by NMPK and dUDP-activated glucose could also substitute dTDP-activated glucose as precursor for the synthesis of activated deoxysugars (see below). The excellent enzyme stabilities under synthesis... 

Controlled Polymerization of Styrene Using In situ Generated Nitric Oxide [Nitrooxide-Mediated Polymerization NMP]... 

Homocoupling of alkenyl halides 1,3-dienes. Alkenyl bromides or iodides couple to 1,3-dienes in the presence of NiCl, zinc (excess), and K1 in HMPT, N-methyl-2-pyrrolidone (NMP), or tetramethylurea. The actual catalyst is Ni(0), generated in situ by zinc and Kl. Unfortunately, the reaction is not stereosf>ecific. 

The discovery of the above-mentioned class of highly efficient alkyne carbonylation catalysts originated from a general study of reactions homogeneously catalyzed by cationic metal complexes [6, 8, 9], e. g., the methoxycarbonylation of propyne (eq. (2)). The catalysts applied were cationic palladium phosphine systems prepared in situ from three components (1) palladium acetate, (2) an excess (10-40-fold on Pd) of a (mono)phosphine ligand(L) and (3) an acid (HX) [8]. Methanol was used as both reactant and solvent, but many other solvents can also be used, such as A-methyl-2-pyrrolidone (NMP) or product MMA. 

Suzuki and Stille couplings. For coupling of aryl chlorides with arylboronic acids the catalytic system contains (CyjPjjPdClj, CsF in NMP. co-Arylalkanoic acids are prepared by coupling of aryl halides with carboxylic esters bearing a 9-BBN substituent at the other terminus, and saponification. A biaryl synthesis from two different aryl halides is accomplished with in situ boronate formation which depends on the (dppfjPdClj catalyst. For access to aryl boronates either the coupling of aryl triflates with bis(pinacolato)diboron" or that of aryl iodides with pinacolborane may be employed. 

The solubility of the polyimide dictates, to a large extent, the synthetic route employed for the copolymerization. The ODPA/FDA and 3FDA/PMDA polyimides are soluble in the fully imidized form and can be prepared via the poly(amic-ac-id) precursor and subsequently imidized either chemically or thermally. The PMDA/ODA and FDA/PMDA polyimides, on the other hand, are not soluble in the imidized form. Consequently, the poly(amic alkyl ester) precursors to these polymers were used followed by thermal imidization [44]. For comparison purposes, 3FDA/PMDA-based copolymers were prepared via both routes. The synthesis of the poly(amic acid) involved the addition of solid PMDA to a solution of the styrene oligomer and diamine to yield the corresponding poly(amic acids) (Scheme 8). The polymerizations were performed in NMP at room temperature for 24 h at a solids content of -10% (w/v). Chemical imidization of the po-ly(amic-acid) solutions was carried out in situ by reaction with excess acetic anhydride and pyridine at 100 °C for 6-8 h. The copolymers were subjected to repeated toluene rinses in order to remove any unreacted styrene homopolymer. 

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