Showing papers on "Diazomethane published in 1993"
01 Jan 1993
TL;DR: This paper focuses on the preparation of Esters, Amides and Other Fatty Acid Derivatives via Activated Fatty Acids through Esterification and Transesterification, and the use of Diazomethane and Related Reagents.
Abstract: A. Introduction B. Acid-Catalysed Esterification and Transesterification 1. General mechanism 2. Methanolic hydrogen chloride 3. Methanolic sulfuric acid 4. Boron trifluoride-methanol 5. Other acidic catalysts C. Base-Catalysed Transesterification 1. General mechanism 2. Sodium and potassium methoxide catalysts 3. Organic base catalysis D. Diazomethane and Related Reagents 1. Diazomethane and methyl ester preparation 2. Preparation of UV-absorbing and other derivatives E. Pyrolysis of Tetramethylammonium Salts of Fatty acids for the Preparation of Methyl Esters F. Preparation of Esters and Amides via Activated Fatty Acids 1. Acid halides 2. Fatty acid anhydrides 3. Imidazolides 4. Other coupling reagents G. Reaction of Alkyl or Aryl Halides with a Base 1. Derivatives for gas chromatography 2. Phenacyl esters and other derivatives for high-performance liquid chromatography H. Alternative Methods for the Preparation of Esters, Amides and Other Fatty Acid Derivatives 1. Dimethylsulfate with dicyclohexylamine 2. Preparation of esters with alkyl formamide derivatives 3. Trimethylsilyl esters 4. Preparation of pyrrolidides from esters 5. Preparation of hydroxamic acid and related derivatives 6. Reaction with Grignard reagents I. Special Cases 1. Short-chain fatty acids 2. Fatty acids with unusual structures 3. Sphingolipids and other N-acyl lipids 4. Sterol esters 5. Selective esterification of free fatty acids in the presence of other lipids J. Preparation of Esters in the Presence of Adsorbents for Thin-Layer Chromatography K. Simultaneous Extraction from Tissues and Transesterification L. Artefacts of Esterification Procedures M. The Choice of Reagents a Summary
521 citations
TL;DR: In this paper, the synthesis of a new synthesis of poly(0-hydroxybutyrate), called syn-PHB, with a preference for syndiotactic (syn) placement was reported.
Abstract: In this report, we havedocumented the ability of tributyltin methoxide, SnBu30CH1, to catalyze the ring-opening polymerization of 0-butyrolactone, BL, with a preference for syndiotactic (syn) placement. This has therefore resulted in the chemical synthesis of a new stereoisomeric form of poly(0-hydroxybutyrate), PHB, specifically syn-PHB, which has predominantly alternatingR and S stereocenters. The polymerization of racemic BL catalyzed by SnBu30CH3 was carried out at temperatures of 40,60,75, and 90 "C. The yields of hexane/ether (l/l) insoluble PHB ranged from 24 to 69%, with the highest yield for the polymerization temperature of 75 "C. An analysis of the stereochemical sequence distribution for the syn-PHB stereoisomers by '"C NMR allowed the degree of syndiotacticity achieved as a function of the polymerization conditions to be quantitated. Thus, it was determined that the racemic (r) diad fractions were 0.70,0.66,0.63, and 0.61 for the polymerization temperatures of 40, 60, 75, and 90 "C, respectively. Therefore, the degree of syndiotacticity decreased for higher polymerization temperatures, as was anticipated; however, the degree of change was unexpectedly small over the 50 "C temperature range investigated. The M, values of the syn-PHB samples ranged between approximately 2500 and 5300 and were determined both by lH NMR spectroscopy end group analysis (after derivatization of the products with diazomethane) and by VPO. These M,, values were approximately 72% of that calculated by the assumption that the number of polymer chains is equivalent to the number of moles of catalyst added. In addition, by analysis using 'H NMR of the number of methyl ester end groups which were present on the syn-PHB samples before and after diazomethane derivatization, it was determined that the ratio of carboxylic acid to methyl ester end groups ranged from 2.5 to 3.1. These results suggest that lactone polymerization by SnBu30CH3 is not solely initiated by an insertion mechanism between the tin-methoxide bond. The syn-PHB polymers when isolated by solution precipitation and analyzed by DSC showed three distinct endotherm component peaks with peak temperatures of approximately47,62, and 79 "C where the dominant endotherm component was, in all cases, at approximately 62 "C. Dramatic changes in the endothermic melting transitions were observed when the samples were melt annealed as opposed to solution precipitated. The X-ray diffractogram for the 70-syn-PHB sample and the calculated d-spacings were compared to those of natural-origin (R)-PHB. Specific d-spacings measured at 7.52,5.40,3.83, and 3.11 A for the 70-syn-PHB sample were not observed for (R)-PHI3 end are evidence for the existence of a different crystalline structure than that determined for an isotactic PHB stereoisomer. FTIR analysis of the 70-syn-PHB sample revealed spectral features which were unique to the conformational order and crystalline structure of this new PHB stereoisomer. Specifically, the appearance of a new band at approximately 1206 cm-I, with a notable increase in the spectral absorption band at approximately 1103 cm-I.
131 citations
TL;DR: In this article, the principal advances and trends in the application of diazomethane as a methylenating agent in synthetic chemistry using transition and non-transition metal compounds as catalysts are surveyed and analysed.
Abstract: The principal advances and trends in the application of diazomethane as a methylenating agent in synthetic chemistry using transition and non-transition metal compounds as catalysts are surveyed and analysed. The catalytic reactions of diazomethane with olefins, acethylenes, aromatic compounds, ketones, alcohols and amines are examined. A systematic account is given of data concerning the influence of the structure of the initial substrates and of the nature of the catalyst components on the regio- and stereo-selectivity of the reactions considered. The possibilities of the catalytic conversion by diazomethane (generated in situ) of unsaturated compounds into cyclopropane derivatives are considered. The bibliography includes 284 references.
54 citations
TL;DR: In this article, a new synthetic approach to the formal α-vinylation of α-amino acids is described, in which the readily available electrophile, ethylene oxide, serves as the vinyl cation equivalent.
Abstract: A new synthetic approach to the formal α-vinylation of α-amino acids is described, in which the readily available electrophile, ethylene oxide, serves as the vinyl cation equivalent. N-Benzoyl α-amino esters bearing appropriate side-chain protecting groups are deprotonated with lithium diisopropylamide in THF/TMEDA at -78 o C to generate the corresponding dianions. Exposure of these to ethylene oxide results in C-alkylation and lactonization to give the corresponding racemic, α-substituted homoserine lactones 2a-j in 61-85% yield. Next, reduction of diphenyl diselenide with sodium trimethoxyborohydride generates a benzeneselenolate anion equivalent which efficiently cleaves the α-substituted homoserine lactones without competing lactone reduction (69-97% yields for 3a-j following diazomethane workup)
49 citations
TL;DR: In this paper, a series of spiropyrazolines has been synthesized by 1,3-dipolar cycloaddition of E- and Z-3-arylidene-chromanones, -1-thiochromanone, -flavanones, 1-thiosavanones as well as 2-benzylidene 1-indanone with diazomethane.
45 citations
TL;DR: In this paper, cycloadditions of open-chain aliphatic thiones (R 2 C=S, R=ethyl, n-propyl, isopropyl, and tert-butyl) to diazomethane mixtures of regioisomers were obtained.
Abstract: In cycloadditions of open-chain aliphatic thiones (R 2 C=S, R=ethyl, n-propyl, isopropyl, and tert-butyl) to diazomethane mixtures of regioisomers were obtained; the ratio depends on R and solvent polarity. Ab initio RHF and CASSCF calculations (3-21G * , 6-21G * ,CAS/-21G * ) and semiempirical calculations (AM1 and MNDO-PM3) are carried out on ground states, possible transition structures, and intermediates
42 citations
TL;DR: In this paper, a method is described to overcome the thermal instability of sulfonylurea herbicides and thus enable their analysis by gas chromatography (GC), and substantial quantities of the N-N'-dimethyl derivatives of chlorsulfuron and metsulfuron-methyl were formed, which were characterized by GC-MS.
Abstract: A method is described to overcome the thermal instability of sulfonylurea herbicides and thus enable their analysis by gas chromatography (GC). Methylation of chlorsulfuron by diazomethane in a variety of solvents usually yielded N-methylchlorsulfuron as the predominant product. This derivative was not stable to GC conditions, forming the N-methylsulfonamide. With diazomethane in either acetone or ethyl acetate and with longer reaction times substantial quantities of the N-N'-dimethyl derivatives of chlorsulfuron and metsulfuron-methyl were formed, which were characterized by GC-MS (EI and CI)
41 citations
Abstract: The cycloaddition reactions of several phenylsulfonyl-substituted allenes with diazomethane have been investigated. The major products formed were identified as 3-(phenylsulfonyl)-4-methylene-2-pyrazolines. These pyrazolines engage in a variety of mechanistically interesting transformations, ranging from base-catalyzed rearrangements to addition of Grignard regents. The dipolar cycloadduct derived from the reaction of diazomethane with 3-(phenylsulfonyl)-1,2-butadiene undergoes a 1,3-phenylsulfonyl shift upon irradiation to give 3-methyl-4-[(phenylsulfonyl)methyl] pyrazole. The cycloadduct derived from the reaction of 2,3-bis(phenylsulfonyl)-1-propene with diazomethane readily loses nitrogen upon photolysis to give 1-[(phenylsulfonyl)methyl]-1-(phenylsulfonyl)cyclopropane
38 citations
TL;DR: In this paper, enolates derived from bicyclic lactones of type 1 (Scheme I) can be alkylated with 2-propynylic halides to give products 2, in which the unsaturated alkyl group is syn to the adjacent ring-fusion hydrogen.
Abstract: Enolates derived from bicyclic lactones of type 1 (Scheme I) can be alkylated with 2-propynylic halides to give products 2, in which the unsaturated alkyl group is syn to the adjacent ring-fusion hydrogen. Reaction of 2 with sodium phenyl selenide and then with diazomethane produces esters 3, and these give trans ring-fused bicyclic compounds 4 when treated with triphenyltin hydride in the presence of a radical initiator. The bicyclic compounds afford ketones on double-bond cleavage, and the angular ester function can be converted into a methyl group. Similar processes occur if an aldehyde is used in the first step instead of a halide. The methodology is general
36 citations
TL;DR: In this paper, an intermediate thiocaronyl ylide of type E (Scheme 4), generated by the 1.3-dipolar cycloaddition of diazomethane with the exocyclic CS bond of 1 and elimination of N2, has been established by X-ray crystallography.
Abstract: Reaction of 1,3-Thaiazole-5(4H)-thiones and Diazometane
Reaction of 4,4-dimethyl-1,3-thiazol-5(4H)-thiones 1 with diazomethane in Et2O at −78° or 0° leads to a mixture of the corresponding 1,4-dithiane 10,1,3-dithiole 11, thiirane 12, 4,5-dihydro-5methylidene-1,3-thiazole 13, and 1,3-thiazol-5(4H)-one 14 (Scheme 3). The structures of 10a, 11a, and 11bhave been established by X-ray crystallography. The formation of the products can be explained via an intermediate thiocaronyl ylide of type E (Scheme 4), generated by the 1.3-dipolar cycloaddition of diazomethane with the exocyclic CS bond of 1 and elimination of N2. Head-to-head dimerization of E yields 10, 1, 3-dipolar cycloaddition of E and 1 gives the ‘Schonberg product’ 11, and cyclization of E leads to 12, which undergoes a desulfurization to give 13. The thiazolone 141 is formed by hydolysis of E. The similarity of the ratio of the products at −78° and at 0° shows that, in contrast to the reaction of 1 and 2-diazopropane, the elimination of N2 in the primary cycloadduct already occurs at −78°.
35 citations
TL;DR: In this article, the stereospecific total synthesis of the naturally occurring macrolide patulolide C 19Eb as well as its iso, nor, and homo analogs is described by applying the photoinduced rearrangement of enantiomerically pure epoxy diazomethyl ketones 14 to γ-hydroxy α,β-unsaturated esters 15 as the key step.
Abstract: The stereospecific total synthesis of the naturally occurring macrolide patulolide C 19Eb as well as its iso, nor, and homo analogs is described by applying the photoinduced rearrangement of enantiomerically pure epoxy diazomethyl ketones 14 to γ-hydroxy α,β-unsaturated esters 15 as the key step. The required epoxy diazomethyl ketones 14 are obtained by a Sharpless epoxidation of an appropriate allylic alcohol, followed by ruthenium tetraoxide oxidation to an oxiranecarboxylic acid, conversion into a mixed anhydride, and treatment with diazomethane. Macrolide 19Zb, which is a geometrical isomer of 19Eb, turned out to be a diastereomer of natural macrolide isopatulolide C, which implies the 4R,11R configuration for this natural material. X-ray diffraction analyses of 19Ea and 19Eb show that there is a considerable difference in spatial arrangement; particularly, the different torsion angles between the carbonyl and olefinic bonds are noteworthy. The conformational behavior of these macrolides is also deduced from the NMR and UV spectra
TL;DR: In this paper, the reactivities of perchlorodiphcnyl carbene (2a) generated by photolysis of 1a were investigated not only in terms of product analysis but also by using flash photo-lysis techniques.
Abstract: Bis(pentachlorophenyl)diazomethane (1a) was prepared, and reactivities of perchlorodiphcnylcarbene (2a) generated by photolysis of 1a were investigated not only in terms of product analysis but also by using flash photolysis techniques. Although the major reaction found for 2a was dimerization forming perchlorotetraphenylethylene and was essentially similar to that observed for 2,2',4,4',6,6'-hexachlorodiphenylcarbene (2b), product distribution clearly indicated that the carbenic center in 2a is more rigidly protected than that in 2b by the four ortho chloro substituents which are buttressed by the four meta chloro groups
TL;DR: In this article, photolysis of [bis(dicyclohexylamino)phosphanyl](trimethylsilyl)diazomethane leads to the corresponding stable carbene, which reacts with triethylborane affording a borane-carbene adduct.
Abstract: Photolysis of [bis(dicyclohexylamino)phosphanyl](trimethylsilyl)diazomethane leads to the corresponding stable carbene1b, which reacts with triethylborane affording a borane–carbene adduct2b, characterized by spectroscopy in solution before rearrangement and fragmentation into P-dicyclohexylamino-C-(ethyl)(trimethylsilyl)phosphaalkene3b; trimethylsilyltrifluoromethanesulfonate adds to 1b giving the methylenephosphonium4b.
Patent•
04 Mar 1993
TL;DR: In this article, a positive-working radiation-sensitive mixture is disclosed which contains as essential constituents: a α,α-bis(sulfonyl)diazomethane, which forms a strong acid on irradiation, of the general formula ##STR1## in which R is an optionally substituted alkyl, cycloalkyl, aryl or heteroaryl radical, a compound having at least one C--O--C or C-O--Si--bond which can be cleaved by acid, and a water-insoluble b
Abstract: A positive-working radiation-sensitive mixture is disclosed which contains as essential constituents: a) an α,α-bis(sulfonyl)diazomethane, which forms a strong acid on irradiation, of the general formula ##STR1## in which R is an optionally substituted alkyl, cycloalkyl, aryl or heteroaryl radical, b) a compound having at least one C--O--C or C--O--Si--bond which can be cleaved by acid, and c) a water-insoluble binder which is soluble or at least swellable in aqueous alkaline solutions. The radiation-sensitive mixture according to the invention is notable for a high sensitivity over a wide spectral range. It also exhibits a high thermal stability and does not form any corrosive photolysis products on exposure to light.
TL;DR: In this article, photolysis of ( o -aminophenyl)diazomethane (5 ) in argon at 10 K and flash vacuum pyrolysis (2 ) with subsequent tr
TL;DR: In this paper, on-column trimethyl-silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagent via the loop-type interface.
Abstract: Degradation products obtained under severe alkaline stress of the drug substance ENA 713, a compound developed for the treatment of DAT (dementia of the Alzheimer type), have been identified by on-line coupled reversed phase HPLC-GC-MS as 3-hydroxyaceto-phenone and 3-hydroxystyrene. Their structures were proven by mass spectroscopic investigation of the products obtained by on-column derivatization during LC-GC transfer. On-column trimethyl-silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagent via the loop-type interface. The usefulness of the technique was further demonstrated by the on-column methylation of carboxylic acids with diazomethane solution (using naproxen as model compound). First results are also given of the use of the liquid-liquid extraction unit of the LC-GC interface for extractive derivatization during reversed phase HPLC-GC-MS transfer.
TL;DR: In this article, 6-Alkylidene penems were found to react with diazomethane to give pyrazolines, which were thermolysed to afford the title compounds.
Patent•
09 Apr 1993
TL;DR: In this article, a positive-working radiation-sensitive mixture is disclosed which contains as essential constituents an α-carbonyl-α-sulfonyl -diazomethane, which forms a strong acid on irradiation, of the general formula I ##STR1## in which R 1 and R 2, independently of one another, denote an alkyl-, cycloalkyl-, aryl- or heteroaryl radical b) a compound having at least one C--O--C or C-O--Si bond which can be cleaved by
Abstract: A positive-working radiation-sensitive mixture is disclosed which contains as essential constituents: a) an α-carbonyl-α-sulfonyl-diazomethane, which forms a strong acid on irradiation, of the general formula I ##STR1## in which R 1 and R 2 , independently of one another, denote an alkyl-, cycloalkyl-, aryl- or heteroaryl radical b) a compound having at least one C--O--C or C--O--Si bond which can be cleaved by acid, and c) a water-insoluble binder which is soluble or at least swellable in aqueous-alkaline solutions. The radiation-sensitive mixture according to the invention is notable for a high sensitivity over a wide spectral range. It also exhibits a high thermal stability and does not form any corrosive photoylsis products on exposure to light.
TL;DR: By reaction of methanebisphosphonate 9 with NaH/diethyl chlorophosphite and in situ oxidation with atmospheric oxygen the methanetrisphosphonic acid hexaethylester 10 in moderate yields, but in pure form is available as mentioned in this paper.
Abstract: Durch Reaktion des Methanbisphosphonsauretetraethylesters 9 mit NaH/Phosphorigsaurediethylesterchlorid und anschliesender Oxidation mit Luftsauerstoff ist der Methantrisphosphonsaurehexaethylester 10 in masiger Ausbeute, aber in reiner Form zuganglich. Die gleiche Verbindung entsteht aus Bis-(diethylphosphono)diazomethan 11 mit Diethylphosphit in Gegenwart von Cu-Acetylacetonat. 10 kann mittels BTMS/H2O in die Trisphosphonsaure 13 uberfuhrt werden, die sich als stabile Verbindung erwies. By reaction of methanebisphosphonate 9 with NaH/diethyl chlorophosphite and in situ oxidation with atmospheric oxygen the methanetrisphosphonic acid hexaethylester 10 in moderate yields, but in pure form is available. The same product is formed from tetraethyl diazomethane diphosphonate 11 and diethylphosphite in presence of Cu-acetylacetonate. 10 can be transformed using the BTMS/H2O-method to the trisphosphonic acid 13, which is a stable compound.
TL;DR: The reaction of selenobenzophenones with diazomethane afforded the corresponding diarylethylenes and symmetrical olefins as discussed by the authors, and this reaction proceeded through selenadiazoline intermediates and retrocyclization was observed.
Abstract: The reaction of selenobenzophenones with diazomethane afforded the corresponding diarylethylenes and symmetrical olefins. The reaction with other diazoalkanes gave three different types of olefins. This reaction proceeded through selenadiazoline intermediates and retrocyclization was observed.
TL;DR: In this paper, base-catalysed addition of the keto ester 15 and 3-methylbut-3-en-2-one gave the hydroxycyclohexanone 16, which was regioselectively converted into the butenolide by oxidation using bromine in methanol and hydrolysis of the mixture of intermediate dimethoxydihydrofurans 24.
Abstract: Stereoselective base-catalysed addition of the keto ester 15 and 3-methylbut-3-en-2-one gave the hydroxycyclohexanone 16. Reduction and methylation gave the monomethyl ether 23, which was regioselectively converted into the butenolide 25 by oxidation using bromine in methanol and hydrolysis of the mixture of intermediate dimethoxydihydrofurans 24. Bromination of the butenolide 25 followed by hydrolysis gave the hydroxybutenolide 40 which was condensed with the ylide generated from the phosphonium salt 62 to give the conjugated dienes 63 and 64. Treatment with a trace of iodine induced (Z)- to (E)-isomerisation of the 10,11-double bond, and ester exchange under basic conditions with 2-(trimethylsilyl) ethanol followed by esterification with diazomethane gave the diesters 67 and 70. Deprotection gave a mixture of the hydroxy acids 71 and 72, and the hydroxy acid 71 was cyclised to give the macrolide 73. Reduction of the methyl ester gave the alcohol 74, a macrocyclic analogue of non-aromatic β-milbemycins.
TL;DR: In this article, a redish orange spot at R f 0.75 on a silica gel plate developed with chloroform-methanol-water as a solvent was derived from all of the cochineal color preparations when they were methylated.
Abstract: Methylation with ethereal diazomethane in THF was applied to detect cochineal color by TLC. A reddish orange spot at R f 0.75 on a silica gel plate developed with chloroform-methanol-water as a solvent was derived from all of the cochineal color preparations when they were methylated. The chemical structure of the spot component employs as indicator compound of cochineal color was characterized as 3,6-di-O-methylcarminic acid methyl ester by physicochemical analysis, UV-vis, IR, 1 H and 13 C NMR, and MS
TL;DR: In this article, the 1,3-dipolar cycloaddition reaction of diazomethane to 7-oxabicyclo[2.2.1]hept-5-ene derivatives substituted on C-2 is discussed.
Abstract: The regioselectivity of the 1,3-dipolar cycloaddition reaction of diazomethane to 7-oxabicyclo[2.2.1]hept-5-ene derivatives substituted on C-2 is discussed. The observed ratio of regioisomers depends upon the nature of the substituents on C-2 and may be accounted for in terms of TS asyncrony for concerted processes
TL;DR: In this article, the structure of 2-(2-oxopropylthio)benzoxazoles with an excess of primary amines in acetic acid or in perchloric acid was confirmed by an X-ray analysis of compound 4d.
TL;DR: In this paper, a bis(polyfluoroalkyl)diazomethanes were obtained in high yield by the oxidation of polyfluorinated ketone hydrazones with bromine in water.
TL;DR: In this paper, the synthesis and 14C-labeling of 3 alpha, 7 alpha, 12 alpha-trihydroxy-27-carboxymethyl-5 beta-cholestan-26-oic acid by two different approaches is described.
TL;DR: In this paper, the reaction of 1 with diazomethane in MeOH gave the ketone 2 as well as the diepoxide 4 and the alcohol 3, obtained by hydrolysis of 2 was acetylated and oxidized to give 6.
TL;DR: Several chlorophenoxy acids and chlorinated phenols were determined by means of gas chromatography in contaminated samples of cereals by providing the highest selectivity of detection and good sensitivity--5 ppb--was achieved.