Subject dimethylformamide

Roughly speaking, we may say that dimethylformamide acts in a way analogously to alcohols, with the difference of having its H-bond acceptor and donor functions in sterically distant sites compared to the —OH moiety. The prevailing recognition pattern can be subject to alterations, giving an individual touch to the associate in question, nevertheless it may be traced back to its characteristic form. 

For the solution-phase preparation of functionalized tropanylidenes, the authors simply dispensed solutions of the bromo N-H precursor in 1,2-dichloroethane (DCE) into a set of microwave vials, added the aldehydes (3 equivalents) and a solution of sodium triacetoxy borohydride in dimethylformamide (2 equivalents), and subjected the mixtures to microwave irradiation for 6 min at 120 °C. Quenching the reductive amination with water and subsequent concentration allowed a microwave-assisted Suzuki reaction (Section 6.1.2) to be performed directly on the crude products [295]. 

The groups of Giacomelli and Taddei have developed a rapid solution-phase protocol for the synthesis of 1,4,5-trisubstituted pyrazole libraries (Scheme 6.194) [356]. The transformations involved the cyclization of a monosubstituted hydrazine with an enamino-/8-ketoester derived from a /8-ketoester and N,N-dimethylformamide dimethyl acetal (DMFDMA). The sites for molecular diversity in this approach are the substituents on the hydrazine (R3) and on the starting j3-keto ester (R1, R2). Subjecting a solution of the /8-keto ester in DMFDMA as solvent to 5 min of microwave irradiation (domestic oven) led to full and clean conversion to the corresponding enamine. After evaporation of the excess DMFDMA, ethanol was added to the crude reaction mixture followed by 1 equivalent of the hydrazine hydrochloride and 1.5 equivalents of triethylamine base. Further microwave irradiation for 8 min provided - after purification by filtration through a short silica gel column - the desired pyrazoles in >90% purity. 

The readily prepared immobilized phosphoramidite could be used to efficiently synthesize oligodeoxyribonucleotides with modified thymidine residues. Whereas the effect of microwave irradiation on the deprotection by exposing the strand to tet-rakis-triphenylphosphine palladium(O) and diethylammonium bicarbonate was only small using dichloromethane as solvent, complete removal of the alloc group was achieved in N,N-dimethylformamide within 10 min at 80 °C (Scheme 7.30). After the reaction, the solid-supported product was washed with N,N-dimethylformamide and dichloromethane and dried, before being subjected to acylation. The coupling... 

The group of Botta demonstrated the feasibility of their microwave-assisted iodi-nation protocol (see Scheme 6.143 d) toward a polymer-supported substrate [68], An appropriate pyrimidinone attached to conventional Merrifield polystyrene resin was suspended in N,N-dimethylformamide, treated with 2 equivalents of N-iodosuccini-mide (NIS), and subjected to microwave irradiation for 3 min. Treatment of the polymer-bound intermediate with OXONE released the desired 5-iodouracil in almost quantitative yield (Scheme 7.57). 

Arylazo-4-(3-ethoxycarbonylureido)furoxans 62, which were synthesized by the reactions of 4-amino-3-arylazo-furoxans with ethoxycarbonyl isocyanate, were subjected to cascade rearrangements under the action of potassium r/-butoxidc in dimethylformamide or by heating in dimethyl sulfoxide to form 4-amino-2-aryl-5-nitro-2//-l,2,3-triazoles 63 (Scheme 13) <2001MC230, 2003RCB1829>. 

Nagai et al. carried out various transformations with camphor-fused amino[l,2,4]triazine 191 <1998JHC293> (Scheme 39). Reaction of 191 with chlorocarbonylsulfenyl chloride yielded the fused thiadiazolone 192 in high yield (83%). The same starting compound also proved to be suitable for the synthesis of the fused triazole derivative 193. To this end, 191 was first subjected to two subsequent transformations first by dimethylformamide dimethylacetal followed by treatment with hydroxylamine hydrochloride to give an Ar-hydroxyamidine 193 in 90% overall yield, and then this compound was treated with polyphosphoric acid to yield the fused triazole product 194 in 92% yield. 

Kemp et al., 1978). The rate is slowest in an aqueous solution and is enhanced in aprotic and/or dipolar solvents. The rate augmentation of 106—108 is attainable in dipolar aprotic solvents such as dimethyl sulfoxide and hexamethylphosphoramide (HMPA). Interestingly, the decarboxylation rate of 4-hydroxybenzisoxazole-3-carboxylate [53], a substance which contains its own protic environment, is very slow and hardly subject to a solvent effect (1.3 x 10-6 s-1 in water and 8.9 x 10-6 s-1 in dimethylformamide Kemp et al., 1975). The result is consistent with the fact that hydrogen-bonding with solvent molecules suppresses the decarboxylation. 

In one study of the effects of additives,9 it was found that on electrochemical oxidation of rubrene, emission was seen in dimethylforma-mide, but not in acetonitrile. When water, n-butylamine, triethylamine, or dimethylformamide was added to the rubrene solution in acetonitrile, emission could be detected on simply generating the rubrene cation.9 This seems to imply that this emission involves some donor or donor function present in all but the uncontaminated acetonitrile system. The solvent is not the only source of impurity. Rubrene, which has been most extensively employed for these emission studies, is usually found in an impure condition. Because of its relative insolubility and its tendency to undergo reaction when subjected to certain purification procedures, and because the impurities are electroinactive and have relatively weak ultraviolet absorptions, their presence has apparently been overlooked, They became evident, however, when quantitative spectroscopic work was attempted.70 It was found, for example, that the molar extinction coefficient of rubrene in benzene at 528 mjj. rose from 11,344 in an apparently pure commercial sample to 11,980 (> 5% increase) after repeated further recrystallizations. In addition, weak absorption bands at 287 and 367 m, previously present in rubrene spectra, disappeared. 

Crosslink density of PU films. The PU films were subjected to swelling tests in dimethylformamide. The crosslink densities of the films were thereafter estimated from equilibrium swelling data using a modified version of the Flory-Rehner equation. The swelling tests as well as the calculation of crosslink density are described in detail in a previous paper (6). 

Analytical Methods. The samples of PAH were extracted with cyclohexane, and the extract was subjected to liquid-liquid extractions with N,N-dimethylformamide as reported elsewhere (26). Following a concentration step, the extract was analyzed by GCZ using a Carlo Erba Fractovap 2101 equipped with a flame ionization detector. The column was a 50 m x 0.32 mm i.d. persilanized glass capillary coated with 0V-73 according to the Grob method (27). 

Seiji et al. (1992) studied the effects of occupational exposure to dimethylformamide on sister chromatid exchange rates in peripheral lymphocytes from 22 dimethylformamide-exposed women (aged 22-52 years) in comparison with 22 sex-, age- and residence-matched controls. All subjects were non-smokers and non-drinkers of alcohol as confirmed by medical interview. The 22 pairs were divided into three subgroups according to the intensity of their exposure to dimethylformamide high exposme (8 pairs with mean exposme of... 

To a solution of L-threonine allyl ester hydrochloride [22,42] (6.0 g, 30.6 mmol, the corresponding hydrotrifluoroacetate or hydrotoluenesulfonate can also be used) in saturated NaHCOj solution (100 mL) and dioxane (100 mL) is added dropwise at 0°C a solution of 9-fiuorenylmethyl chloroformate (10.8 g, 41.8 mmol) in dioxane (50 mL). After stirring for 24 h, the solvent is evaporated in vacuo, the remainder dissolved in ethyl acetate (200 mL), washed with 0.5 N HC1, saturated NaHCOj solution, and water (each 100 mL), dried with MgS04, and concentrated in vacuo. The crude product is subjected to chromatography on silica gel (300 g) in petroleum ether-ethyl acetate (4 1), and the obtained product is recrystallized from ethyl acetate-petroleum ether to give pure 24 yield, 11.2 g (96%) mp 98°-100°C [a]D -17.2° (c 1, dimethylformamide) R, 0.33 (petroleum ether-ethyl acetate 2 1). 

In the synthesis of the 1 1 cobalt complex 17 by the nitrite method, a mixture of CoS04-7 H20 and NaN02 in water and the dye formed by acid coupling of diazotized 2-amino-4,6-dinitrophenol with 2-phenylaminonaphthalene-4 -sulfonic acid is subjected to dropwise addition of dimethylformamide. Metallization commences immediately and is complete within 2 h. The 1 1 cobalt complex 17 is precipitated by addition of NaCl and isolated. It is a suitable intermediate for producing unsymmetrical 1 2 cobalt complex dyes such as 18. 

Dimethyl malonate (4.04 g, 30.6 mmol), potassium t-butoxide (3.43 g, 30.6 mmol) and anhydrous N,N-dimethylformamide (15 ml) were mixed and stirred for 10 minutes in a nitrogen atmosphere at 90°C. The mixture was then cooled to room temperature, and to the cooled mixture was added a solution of diethyl 2-(3-chloro-4-nitrophenyl)-2-methylmalonate (5.04 g, 15.3 mmol) prepared in the manner as described in Japanese Patent Publication No. 47-45, 746) in anhydrous N,N-dimethylformamide (15 ml). The resulting mixture was stirred at 90°C for 3 hours, and then poured into 1 N hydrochloric acid (30 ml). The mixture was subjected to extraction using two portions of diethyl ether. The ether extracts were combined, washed successively with water and an aqueous saturated sodium chloride solution, and dried over anhydrous sodium sulfate. The dried extract was placed under reduced pressure to give 7.97 g of yellow oil. The oil was adsorbed on silica gel (16 g) and subjected to... 

A mixture of 2-chlorothiazole (5.0 g), ethyl 2-(4-hydroxyphenyl)propionate (8.1 g), potassium carbonate powder (8.65 g) and dimethylformamide (80 ml) is stirred at 150°-155°C for 2.5 hours. The solvent is distilled out under reduced pressure. To the residue is added water and extracted with ether. The extract is washed with a 10% aqueous solution of sodium hydroxide and water and dried. The ether is evaporated. The residue is subjected to chromatography using silica gel and eluted with 50% benzene-hexane, benzene and 10% ether-benzene to yield ethyl 2-[4-(2-thiazolyloxy)-phenyljpropionate (5.8 g). 

Metal hydride reduction of methyl dehydroabietate (64b) afforded alcohol (65) whose tosyl derivative on heating with sodium iodide and zinc in dimethylformamide yielded (66). The use of hexamethylphosphoramide gave an inferior yield of (66). Regio and stereoselective acetoxylation with Pb(OAc)4 in acetic acid at 100°C gave only 30% yield of (67) but the same experiment realized with Pb(OAc)4 using a Hg medium-pressure lamp at room temperature yielded (67) in 74%. The H NMR spectrum of (67) showed that the OAc group was introduced in 7a-position. This on subjection to acid-catalyzed 13-elimination (EtOH/10% HC1) produced (68) in quantitative yield. 

This type of reaction with A N-disubstituted formamides, giving aldehydes, was an early application of Grignard reagents, sometimes known as the Bouveault reaction [A]. Dimethylformamide and N-methylformanilide, PhN(Me)CHO, have been most commonly used, but more recently iV-formylpiperidine and 2-(/V-formylmethylamino)pyridine have been recommended examples are listed in Table 6.5, and a recent example of the traditional procedure follows. It should be noted that these reactions are subject to a number of side-reactions [A]. One useful one is the formation of enamines by elimination from the initial adduct [9] ... 

The occasional preliminary purification of products by aqueous washes usually coincides with the use of pyridine or dimethylformamide as solvent. Esters such as succinimido and benzotriazolyl are often prepared in situ, meaning that they are not isolated but subjected to aminolysis immediately after the esterification reaction.P " Slight decomposition can accompany the esterification of Boc amino acids, in particular if dichloromethane is used as solvent and the acidic EDC is used as reagent.P l Publications with a major focus on the synthesis of active esters using DCC are listed in Table 2. A list of Fmoc-Xaa-OR active esters that had been described to 1987 has been compiled.f l... 

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