Dechlorination of N-chloro poly(hexamethylene adipamide) and N-chloro poly(ε-caprolactam) products to the corresponding polyamides

A rapid dechlorination method of N-chloro poly(hexamethylene adipamide) and N-chloro poly(ε-caprolactam) to the corresponding polyamides was studied. This method can be used for molecular weight determinations of N-chloro polyamides by viscosimetric measurements. The dechlorination was achieved in formic acid solution by the reaction of N-chloro polyamides with trialkyl phosphites. The reaction was exothermic and vigorous and was applied to a series of products of various degrees of N-chlorination covering the range of 0–100%. No N—Cl was detected by iodimetric titration of the dechlorination products. The dechlorination of N-chloro polyamides was demonstrated by infrared (IR) spectroscopy. No significant molecular weight reduction except that taking place in the N-chlorination reaction of poly(hexamethylene adipamide) was observed.     

Enantioselective α-chlorination of β-oxo esters catalyzed by chiral diterpenoid alkaloid derivatives

Easily accessible diterpenoid alkaloid derivatives have been used as organocatalysts in the enantioselective α-chlorination of β-oxo esters. The treatment of β-oxo esters with N-chlorophthalimide (NCP) as a chlorine source under mild reaction conditions afforded the corresponding α-chlorinated β-oxo esters in excellent yields (up to 98%) and with moderate enantioselectivities (up to 68% ee) in 30 min.     

Kinetics of the N-chlorination of 2-aminobutyric, 3-aminobutyric, 3-aminoisobutyric and 4-aminobutyric acids in aqueous solution

We studied the kinetics of the N-chlorination of 2-aminobutyric, 3-aminoisobutyric, and 4-aminobutyric acids by sodium hypoclorite in strongly alkaline aqueous solution. As in the case of other amines, the rate of formation of the four N-chloroamino acids was proportional to the concentrations of hypochlorite and amino acid, and inversely proportional to the concentration of hydroxyl ions. A reaction mechanism compatible with these results is proposed and discussed. © John Wiley & Sons, Inc.     

Investigation of the Organocatalytic Chlorination of 2-Phenylpropanal

Results of an examination of the organocatalytic enantioselective α-chlorination of 2-phenylpropanal are described. Synthetic investigation including the screening of primary and secondary aminocatalysts, many different reaction conditions, and other α-branched aldehydes show that especially primary aminocatalysts can catalyze the formation of the α-chloro branched aldehydes in good yields, but only with moderate enantioselectivities. In order to try to understand the challenge in obtaining high enantioselectivity for the aminocatalytic α-chlorination of α-branched aldehydes a series of experimental investigations were performed employing 2-phenylpropanal as a model system. These investigations have been coupled with computational investigations, which provided important insight into the moderate enantioselectivity of this chlorination reaction. Analysis of the reaction showed, that the lack of control over the selectivity of formation of the (E)- and (Z)-enamine intermediate, and the clustering of reaction barriers of possible reaction pathways help to rationalize difficulties in producing high enantioselectivity.     

Skeletal rearrangement of 3-methoxy-N-chloromorphinan

3-Methoxymorphinan ( 1 ) was converted to the corresponding N-chloro derivative 2 by treatment with aqueous sodium hypochlorite. Upon exposure to methanolic silver nitrate, 2 was rearranged to the carbinolamine ether 3 . In addition, considerable amounts of the dechlorinated morphinan 1 were formed. The structure of 3 was secured by spectral analysis and its degradation to the hexahydroindoline derivative 4 . The observed skeletal rearrangement of 2 which requires the migration of an alkyl group is discussed in terms of a nitrenium ion.     

Chlorination of N-Methylacetamide: A kinetic study

In the pH range 4.3–13, the reaction between N-methylacetamide (NMA) and sodium hypochlorite in dilute aqueous solution to give N-chloro-N-methylacetamide (CINMA) was found to be far slower than analogous reactions affording N-chloramines or N-chloroamino acids. The rate expression for chlorination was first-order each in [NMA] and [Cl_tot] (the total concentration of chlorinating species). A rate constant calculated for chlorination by each chlorinating species indicated that the order of increasing reactivity was HClO < ClO^? < Cl₂ < CH₃COOCl (formed in the presence of acetic/acetate buffer). At pH > 7 the reaction rate was unaffected by variations in [Cl^?] or pH, but under acidic conditions the rate increased with [Cl^?] and decreasing pH. Regardless of pH, the reaction rate was not affected by changes in ionic strength. The influence of temperature on the reaction rate was also studied which allowed calculation of thermodynamic activation parameters for the N-chlorination reaction. © 1995 John Wiley & Sons, Inc.     

Synthesis of 6β-Halogenodeoxyneopine from Neopine

(-)-Neopine (1), the Δ^8,14 isomer of codeine, occurs as one of the minor constituents in opium from Papaver somniferum L¹. In opium alkaloids of the morphine group the hydroxyl group in position 6 is readily converted with p-toluenesulfonyl chloride or methanesulfonyl chloride into the respective 6α-O-sulfonyl derivatives². The latter in turn form starting materials for the preparation of other derivatives. Thus, with lithium halides, via a S_N2 mechanism³ the 6β-halogen compounds are formed. It is found that, as a result of the allylic system, under slightly changed reaction conditions codeine itself can also yield the 8β-chloro derivative⁴.     

Effects of catalysts on chlorination of propionic acid

Chlorination of propionic acid with molecular chlorine at 100–130° in the dark giving various chlorinated propionic acids has been studied. Information concerning the product distribution and the effect of some addenda on the distribution has been obtained. There seems to be a competition between the H atom abstraction by radicals and the addition to the enol of carboxylic acid ; the ratio of -chlorination, /( + β), increases in the presence of enolising catalyst such as H₂SO₄, HCl and FeCl₃. The radical scavengers such as m-dinitrobenzene increase the ratio of -chlorination and no chloro acid is formed on addition of more than 1 mol % m-dinitrobenzene in the absence of enolising catalyst. The addition of 3 mol % m-dinitrobenzene m the presence of 95 % H₂SO₄ yields only -chloro acid. The reaction at 120° in the presence of a radical scavenger gives mainly -chloro acid at an early stage and then ,-dichloro acid, the latter yield being 7·7% after 7 hr and 33·6% after 12 hr. The reaction mechanism is discussed.     

Studies on the chemical synthesis of potential antimetabolites. 30. Regioselective introduction of a chlorine atom into the imidazo[4,5-b]pyridine nucleus

Reactions of some imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride are described. Treatment of N-1-substituted imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride led to the predominant formation of 7-chloro derivatives. This feature was successfully applied to the preparation of a chloroimidazo[4,5-b]pyridine nucleoside, which served as an important precursor of 1-deazaadenosine.     

Kinetics of the formation,decomposition, and disproportionation reactions of N-chlorobutylamines

The formation of N-chlorobutylamines is a reaction of order one with respect to hypochlorite and amine, and order ?1 with respect to OH^?. Kinetic studies show that N-chlorobutylamines undergo decomposition in basic aqueous media, and disproportination (with formation of N,N-dichloramines) in acidic media, mechanisms are put forward for both these processes. © 1995 John Wiley & Sons, Inc.     

Reactions of N-Arylsulfonyl-2-arenesulfonamido-1,4-benzo-quinone 4-Imines with Naphthols

Reactions of N-arylsulfonyl-2-arenesulfonamido-1'4-benzoquinone 4-imines unsubstituted in thering or 6-chloro, 5'6-dichlorosubstituted with 1- or 2-naphthols, 2-methoxynaphthalene provided thecorresponding N-arylsulfonyl-2-arenesulfonamido-6-[2-hydroxy(methoxy)-1-naphthyl]-4-aminophenols fromthe unsubstituted reagent and reduction products from the mono- and dichlorosubstituted quinone imines.     

Synthesis of 1-(1,1-dimethylethyl)-1H-pyrazole-4-carboxylate ester derivatives

Attempts to prepare ethyl 5-cyano-1-(1,1-dimethylethyl)-1H-pyrazole-4-carboxylate ( 7 ) by the reaction of the corresponding 5-chloro derivative 1b with cyanide ion were unsuccessful. The chloro ester was synthesized from the corresponding amino ester la utilizing nonaqueous diazotization with nitrosyl chloride. An alternate process was developed which allowed the preparation of 7 from the corresponding 5-methyl ester 3 in four steps. The structure of the N-methylamide 8 synthesized from 7 was confirmed by X-ray diffraction analysis.     

Specific interactions and miscibility of blends of poly(ε-caprolactam) and sulfonated PEEK ionomer

Sulfonation of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), PEEK, improves its miscibility with poly(ϵ-caprolactam), Nylon-6 (N6). This article describes the thermal transitions and the specific interactions that occur for blends of the free acid derivative (H-SPEEK) and the lithium (Li-SPEEK) and zinc salts (Zn-SPEEK) of sulfonated PEEK (19.2 mol % sulfonation) with N6. The interactions responsible for miscibility were characterized by Fourier transform infrared (FTIR) spectroscopy. For blends of H-SPEEK and N6, miscibility is due to hydrogen bonding between the sulfonic acid and the amide group. For blends of N6 with the salts of SPEEK the specific interaction involves an ion-dipole complex of Li⁺ with the amide carbonyl or Zn²⁺ with the amide nitrogen. The relative strengths of the intermolecular interactions for the three types of blends increased as the cation was varied in the order: H⁺ < Li⁺ < Zn²⁺, and the T_gs of the mixtures increased in the same order. © 1996 John Wiley & Sons, Inc.     

Preparation of Nylon-6 Particles in Ionic Liquids

Summary: Utilizing the thermal stability of ionic liquid, micrometer-sized Nylon-6 particles were successfully prepared by hydrolytic polymerization of ε-caprolactam at high temperature with polyvinyl pyrrolidone as stabilizer in ionic liquids, 1-butyl-3-methyl imidazolium tetrafluoroborate, [Bmim][BF₄] and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoro-methanesulfonyl)amide, [DEME][TFSA]. The obtained particles had a unique shape because Nylon-6 is a crystalline polymer. Viscosity-average molecular weights of Nylon-6 prepared in [Bmim][BF₄] and [DEME][TFSA] at 180 °C for 48 h were 4200 and 2200, respectively.     

Pyrimidines. 7. A study of the chlorination of pyrimidines with phosphorus oxychloride in the presence of N,N-dimethylaniline

The chlorination of 6-trifluoromethyluracils by phosphorus oxychloride in the presence of N,N-dimethylaniline was studied and compared with results obtained with 6-methyluracils. 6-Trifluoromethyluracil and its 5-chloro analog afforded moderate yields of the di- and trichloropyrimidines, accompanied by good yields of the 2-N-methylanilino by-products, after a 3-hour reaction time. After 24 hours, the 2-N-methylanilinopyrimidines were the primary or sole products. A small yield of 2,4-bis(N-methylanilino)-6-trifluoromethylpyrimidine was also obtained. The 6-methyluracils afforded high yields of the di- and trichloropyrimidines, after 3 and 24 hours, along with minor amounts of the 2-N-methylanilino by-products. After 48 hours, the proportion of 2,4-dichloro-6-methylpyrimidine decreased, and the 2-N-methylanilino product increased. 2-Chloro-4-methylanilino-6-methylpyrimidine and bis(2-N-methylanilino)-6-methylpyrimidine were also formed in small amounts. The chlorination products from 5-chloro-6-methyluracil remained constant over 188 hours of reaction time. It appears that the π electron distribution around the ring, as influenced by the substituents, controls the course of the chlorination and by-product formation. Since the amination by a tertiary amine is a type of Hofmann reaction, the presence of the chlorine in the 5 position of the ring adds steric hindrance and thus enhances the regiospecificity of the formation of by-products.     

The Allyl Ester as Carboxy-Protecting Group in the Stereoselective Construction of Neuraminic-Acid Glycosides

The application of the allyl-ester moiety as protecting principle for the carboxy group of N-acetylneuraminic acid is described. Peracetylated allyl neuraminate 2 is synthesized by reacting the caesium salt of the acid 1 with allyl bromide. Treatment of 2 with HCl in AcCl or with HF/pyridine gives the corresponding 2-chloro or 2-fluoro derivatives 3 and 4 , respectively (Scheme 1). In the presence of Ag₂CO₃, the 2-chloro carbohydrate 3 reacts with di-O-isopropylidene-protected galactose 5 to give the 2–6 linked disaccharide with the α-D -anomer 6a predominating (α-D /β-D = 6:1; Scheme 2). Upon activation of the 2-fluoro derivative 4 with BF₃ · Et₂O, the β-D -anomer 6b is formed preferentially (α-D /β-D = 1:5). In further glycosylations of 4 with long-chain alcohols, the β-D -anomers are formed exclusively (see 10 and 11 ; Scheme 4). The allyl-ester moiety can be removed selectively and quantitatively from the neuraminyl derivatives and the neuraminyl disaccharides by Pd(0)-catalyzed allyl transfer to morpholine as the accepting nucleophile (see Scheme 5).     

SYNTHESIS AND REACTIONS OF HALO DERIVATIVES OF 4-ISOPROPYL-2H-1,4-THIAZIN-3-ONE

Abstract

Reaction of 4-isopropyl-2H-1,4-thiazin-3-one 1 (R [dbnd] i-Pr) with N-chloro- and N-bromosuccinimide occurred exclusively at the 6-position to give 6-chloro and 6-bromo derivatives of 1 (R [dbnd] i-Pr), respectively, in high yield, in sharp contrast to the 2-aroyloxylation by benzoyl peroxide or m-chloroperbenzoic acid reported earlier.² Reaction of 1 (R [dbnd] i-Pr) with methanesulfonyl chloride in the presence of aluminum chloride afforded an addition compound, 4-isopropyl-5,6-dichloro-1,4-tetrahydrothiazin-3-one. The 2-chloro derivative 6 of 1 (R [dbnd] i-Pr) was successfully prepared by hydrolysis of the 2-m-chloroben-zoyloxy derivative of 1 (R [dbnd] i-Pr) followed by treatment with thionyl chloride. Derivative 6 reacted readily under mild conditions with water, alcohols, thiols, ammonia and amines to give various 2-substituted compounds of 1 (R [dbnd] i-Pr). With phenol as a nucleophile, 1 (R [dbnd] i-Pr) reacted exclusively at the para position. Reaction at carbon atoms also occurred with N,N-dimethylaniline and 2,6-xylidine.     

The use of an electrophile carrier to determine the number of intermediates in the chlorination of 1-methylpyrrole

A kinetic and product study of the dichloroacetic acid catalyzed chlorination of 1-methylpyrrole with 3- and 4-substituted N-chlorobenzamides was carried out. Protonated N-chlorobenzamides served as carriers of CI⁺. A Hammett correlation was obtained with ρ=−0.68 (r=0.98, n=8). General acid catalysis was observed with α=0.48 (r=0.99 and n=7). The yields of 2-chlorination (84±0.7%) and 3-chlorination (2.6±0.4%) were essentially constant (constant intramolecular selectivity) as the substituent on the N-chlorobenzamide was varied. Observation of constant intramolecular selectivity indicated that two intermediates were formed during the acid catalyzed chlorination of 1-methylpyrrole with N-chlorobenzamides. The carrier method is applicable to all types of aromatic systems and limited only by the availability of suitable carrier molecules.     

Benzo[b]thiophene derivatives. XXVII. 5-methoxy-6-halo-3-β-acetamidoethylbenzo[b]thiophenes,blocked analogs of melatonin

The preparation of the 6-fluoro and 6-chloro analogs of the title compound is described, in a seven-step synthesis giving 30-40% overall yields. All intermediates have been isolated and characterized, including important by-products, such as the corresponding benzo[b]thienyl-3-acetic acids, and 3-methylbenzo[b]thiophenes. Cyclization of the 3-halo-4-methoxyphenylthioacetoacetic esters gave more ortho-cyclization in the chlorine case than was observed for the fluorine derivative. The title compounds were shown to have weak antiovulatory action, with the fluoro analog most active.     

Ferrous ion induced decomposition of alkyl hypochlorites

The decomposition of primary, secondary and tertiary alkyl hypochlorites induced by ferrous and other one-electron oxidizable metal ions leads to δ-chloro alcohols in yields of 34–76%. In decomposition of tertiary alkyl hypochlorites, β-fragmentation competes with intramolecular δ-chlorination. Tertiary cycloalkyl hypochlorites containing five- or six-membered rings undergo β-cleavage giving the corresponding ω-chloro ketones, while 1-methylcycloheptyl and 1-methylcyclooctyl hypochlorites by decomposition with ferrous ion proceed by transannular functionalization of δ-carbon atom and β-cleavage as a competing reaction.