Showing papers on "Diazomethane published in 1997"

Evaluating acid and base catalysts in the methylation of milk and rumen fatty acids with special emphasis on conjugated dienes and total trans fatty acids

Abstract: Milk analysis is receiving increased attention. Milk contains conjugated octadecadienoic acids (18∶2) purported to be anticarcinogenic, low levels of essential fatty acids, and trans fatty acids that increase when essential fatty acids are increased in dairy rations. Milk and rumen fatty acid methyl esters (FAME) were prepared using several acid-(HCl, BF3, acetyl chloride, H2SO4) or base-catalysts (NaOCH3, tetramethylguanidine, diazomethane), or combinations thereof. All acid-catalyzed procedures resulted in decreased cis/trans (Δ9c, 11t-18∶2) and increased trans/trans (Δ9t, 11t-18∶2) conjugated dienes and the production of allylic methoxy artifacts. The methoxy artifacts were identified by gas-liquid chromatography (GLC)-mass spectroscopy. The base-catalyzed procedures gave no isomerization of conjugated dienes and no methoxy artifacts, but they did not transesterify N-acyl lipids such as sphingomyelin, and NaOCH3 did not methylate free fatty acids. In addition, reaction with tetramethylguanidine coextracted material with hexane that interfered with the determination of the short-chain FAME by GLC. Acid-catalyzed methylation resulted in the loss of about 12% total conjugated dienes, 42% recovery of the Δ9c,11t-18∶2 isomer, a fourfold increase in Δ9t,11t-18∶2, and the formation of methoxy artifacts, compared with the base-catalyzed reactions. Total milk FAME showed significant infrared (IR) absorption due to conjugated dienes at 985 and 948 cm−1. The IR determination of total trans content of milk FAME was not fully satisfactory because the 966 cm−1trans band overlapped with the conjugated diene bands. IR accuracy was limited by the fact that the absorptivity of methyl elaidate, used as calibration standard, was different from those of the other minor trans fatty acids (e.g., dienes) found in milk. In addition, acid-catalyzed reactions produced interfering material that absorbed extensively in the trans IR region. No single method or combination of methods could adequately prepare FAME from all lipid classes in milk or rumen lipids, and not affect the conjugated dienes. The best compromise for milk fatty acids was obtained with NaOCH3 followed by HCl or BF3, or diazomethane followed by NaOCH3, being aware that sphingomyelins are ignored. For rumen samples, the best method was diazomethane followed by NaOCH3.

Hydroxyl Radical-scavenging Effects of Spices and Scavengers from Brown Mustard (Brassica nigra)

Abstract: The effects of methanol extracts of 51 spices on ·OH scavenging were studied in detail. 2-Deoxyribose oxidation and sodium benzoic acid hydroxylation methods were used for detecting the scavenging activity of ·OH. Mustard varieties, thyme, oregano, clove, and allspice all exhibited strong ·OH-scavenging activity. In particular, 3 varieties of mustard had above 90% ·OH-scavenging activity with a 1 μg/ml concentration of their extracts. The ·OH scavenger of Brassica nigra (brown mustard) was isolated and purified by XAD-2 column chromatography and preparative HPLC, and was identified as a 3,5-dimethoxy-4-hydroxycinnamic acid methyl ester by MS, ‘H-NMR, and 13C-NMR. The 3,5-dimethoxy-4-hydroxycinnamic acid methyl ester was prepared by methylating of sinapic acid with diazomethane.

Cyclopropanation with Diazomethane and Bis(oxazoline)palladium(II) Complexes.

Abstract: Studies toward the development of an enantioselective diazomethane-based cyclopropanation reagent derived from bis(oxazoline)palladium(II) complexes are reported. Several simple palladium chelates, 2 and 7, in addition to the novel carbon-bound complexes 15 were synthesized and evaluated in the cyclopropanation of various electron-deficient olefins. The X-ray crystal structure of aryl−bis(oxazoline)palladium complex 15c is described. Although all catalysts efficiently affected cyclopropanation, all products were racemic. An intriguing relationship between substitution on the oxazoline ring, particularly the commonly-derivatized 4-position, and catalyst efficiency was discovered. The results are rationalized by either partial or complete bis(oxazoline) decomplexation during the course of the reaction.

New sulfonyldiazomethane compound

Abstract: PROBLEM TO BE SOLVED: To obtain the new subject compound useful as an acid generating agent in a chemically amplifying type resist manifesting a sufficient sensitivity and resolution. SOLUTION: The objective compound is a sulfonyldiazomethane of formula I (R is a lower alkylene; R is a tertiary alkyl), e.g. bis(4-tert -butoxycarbonylmethyloxyphenylsulfonyl) diazomethane. The compound of formula I is obtained by condensing thiophenol with a methylene halide such as methylene chloride and methylene bromide in an inert solvent by using a dehydrohalogenation agent to provide bis(hydroxyphenylthio) methane, oxidizing the obtained bis(hydroxyphenylthio) methane to provide bis(hydroxyphenylsulfonyl) methane of formula II, reacting a tertiary alkyl ω-halogenoalkanate with the obtained bis(hydroxyphenylsulfonyl) methane, and diazotizing the product.

New diazomethane compound

Abstract: PROBLEM TO BE SOLVED: To obtain the new subject compound useful as an acid generating agent for a chemically amplifying type resist good in resolution, pattern form and rate of a remaining membrane. SOLUTION: This diazomethane compound is the one of formula I [each R is H or forms dimethylmethylene group by binding two Rs in the same ring; R and R are each a lower alkyl; (n) is 0 or 1], e.g. bis[2-(1 -ethoxyethyloxy) cyclohexysulfonyl] diazomethane. The compound of formula I is obtained by reacting a thiol compound with a methylene halide in a solvent such as ethanol in the presence of a hydrogen halide scavenger such as an alkali hydroxide to provide a compound of formula II, oxidizing the obtained compound of formula II with an oxidizing agent such as hydrogen peroxide to provide a bissulfonylmethane body, diazotizing the bissulfonylmethane body to provide a bissulfonyldiazomethane body, reacting the bissulfonyldiazomethane body with an alkoxyalkene by using a catalyst such as pyridinium p-toluenesulfonate, and separating and purifying the product.

Synthesis of pyrazolines by the reactions of α,β-enones with diazomethane and hydrazines (review)

Abstract: The first representatives of pyrazolines were synthesized in the last century. These nitrogen-containing heterocyclic compounds became important in the development of different bioactive substances. For this reason, various procedures have been worked out for their synthesis. In the present article we summarize those synthetic methods providing 1- or 2-pyrazolines by the reactions of α,β-unsaturated ketones with diazomethane or hydrazine derivatives.

Acacia concinna Saponins. II. Structures of Monoterpenoid Glycosides in the Alkaline Hydrolysate of the Saponin Fraction

Abstract: From the AcOEt-soluble fraction of the alkaline hydrolyzate of the highly polar saponin fraction of pods of Acacia concinna, two monoterpenes, (2E)-2, 6-dimethyl-6-hydroxy-2, 7-octadienoic acid (menthiafolic acid, 1) and (2E)-6-hydroxy-2-hydroxymethyl-6-methyl-2, 7-octadienoic acid (4), and their glycosides, (6R)- and (6S)-menthiafolic acid-6-O-β-D-quinovoside (2a and 2b) and (6R)- and (6S)-menthiafolic acid-6-O-β-D-xyloside (3a and 3b), were isolated. A more polar fraction gave, after methylation with diazomethane, (6R)- and (6S)-(2E)-6-hydroxy-2-hydroxymethyl-6-methyl-2, 7-octadienoic acid-6-O-β-D-quinovoside as their methyl esters (5a and 5b). Compounds 2a, 3a, 4, 5a, and 5b are new. The structures of the above compounds were determined mainly by the application of spectroscopic methods.

Synthesis of Enantiomerically Pure Cyclopropyl Boronic Esters

Abstract: The synthesis of enantiomerically pure cyclopropyl boronic esters 12a−d and 13a−d has been achieved. The high-yielding process involves the condensation of readily available alkenyl boronic acids 1a−d with (2R,3R)-1,4-dimethoxy-1,1,4,4-tetraphenyl-2,3-butanediol (10), Pd(II) acetate catalyzed cyclopropanation with diazomethane, and chromatographic separation of the diastereoisomers. The absolute configuration has been determined by converting 12a−d and 13a−d to the corresponding cyclopropanols (1R,2R)-4a+b/(1R,2S)-4c+d and (1S,2S)-4a+b/(1S,2R)-4c+d, respectively, compounds that allowed correlations to be made with previously published data.

First diastereoselective 3+2 cycloaddition of chiral non-racemic alkenyl fischer carbene complexes with diazomethane derivatives

Abstract: (-)-8-Phenylmenthol derived pentacarbonylalkenyl(alkoxy)chromium carbene complexes react with diazomethane derivatives to give only one diastereomer of enantiomerically pure 4,5-dihydro-1H-pyrazoles; the one-pot synthesis of the corresponding esters is also described.

Nitrilimines: Evidence for the Allenic Structure in Solution, Experimental and Ab Initio Studies of the Barrier to Racemization, and First Diastereoselective (3 + 2)-Cycloaddition

Abstract: The lithium salts of [bis(diisopropylamino)thioxophosphoranyl]diazomethane (2) and [(diisopropylamino)(dicyclohexylamino)thioxophosphoranyl]diazomethane diazomethane (5) react with the (diisopropylamino)(dicyclohexylamino)chlorophosphine (3) and bis(diisopropylamino)chlorophosphine (6), leading to the nitrilimines 4 (63% yield) and 7 (69% yield), respectively. The lithium salt of 2 also reacts with the bis(dicyclohexylamino)phosphenium ion, affording nitrilimine 9 in 51% yield. Using the presence of a chiral substituent either at the carbon or at the nitrogen terminus of the CNN skeleton, variable-temperature solution NMR studies of nitrilimines 4 and 7 demonstrate that they possess a bent allenic structure. The free energy of activation for racemization is ca. 30 kJ mol(-1). Ab initio/DFT studies performed on nitrilimine with C-P(S)H-2 and N-PH2 substituents 10 show that the most likely pathway for the racemization process is inversion at the carbon atom, followed by rotation of the PSR(2) fragment. Bis(trityl)nitrilimine 17 reacts with (R)-alpha-(acryloxy)-beta,beta-dimethyl-gamma-butyrolactone, leading to diastereomeric pyrazolines 18a,b (3/1 ratio) in 60% total yield; this is the first example of a diastereoselective [3 + 2]-cycloaddition reaction involving a nitrilimine.

1, 3-Cycloadditions to Highly Substituted, Strained Double Bonds: Spiro β-lactams from α-methylidene-β-lactams by reactions with diphenylnitrilimine, acetonitrile oxide, nitrones, and diazomethane

Abstract: Substituted dihydropyrazole-spiro-β-lactams and isoxazolidine-spiro-β-lactam derivatives are regio- and stereoselectively prepared by 1, 3-cydoadditions between substituted α-methylidene-β-lactams and diazomethane, nitrones, or the in-situ-prepared dipoles ‘diphenylnitrilimine’ and acetonitrile oxide. These reactions represent examples for 1, 3-cycloadditions to the highly substituted, strained double bonds of α-methylidene-β-lactams, and they need special experimental conditions as all reaction products are relatively unstable. Especially in solution, the reverse reaction is highly favoured. Regioselectivity and stereoselectivity of the reactions are elucidated mainly by NMR techniques such as 2D-INEPT, ATP, and NOE experiments.

Synthesis of α-Necrodol: Unexpected Formation of a Cyclopropene

Abstract: Significant 1,3-induction in intramolecular alkylidene C−H insertion is reported. Thus, exposure of ketone I to the lithium salt of (trimethylsilyl)diazomethane provides a 2.4:1.0 ratio of IIa and IIIa, which are deprotected to α-necrodol IIb and the epimeric IIIb. The 1,3-insertion product cyclopropene IV was also formed.

Ozonolyses of Acetylenes: Trapping of α-Oxo Carbonyl Oxides by Carbonyl Compounds and Stabilization of α-Oxo Ozonides by Derivatizations

Abstract: Ozonolyses of 2-butyne (7) or of 3-hexyne (14) in the presence of carbonyl compounds (aldehydes, ketones, acid derivatives) afforded the corresponding mostly labile monocyclic α-oxo ozonides (9, 13a, 16), which could be stabilized and, hence, isolated by subsequent conversion into α-methoximino derivatives. Ozonolyses of 1,4-diacyloxy-substituted (19) and 1-acyloxy-substituted 2-butynes (27) gave bicyclic ozonides (22, 31) by intramolecular [3 + 2]-cycloadditions of the corresponding carbonyl oxide intermediates (20, 29). These ozonides could also be stabilized by reactions with O-methylhydroxylamine to give O-methyloximes (23c, 32) or with diazomethane to give epoxy ozonides (25, 34).

Continuous process for diazomethane from an n-methyl-n-nitrosoamine and from methylurea through n-methyl-n-nitrosourea

Abstract: Diazomethane is produced in a continuous process with little or no explosion hazard, by dissolving an N-methyl-N-nitroso amine in a mixture of a water-miscible organic solvent that dissolves the N-methyl-N-nitroso amine and a water-immiscible organic solvent that dissolves diazomethane, and combining a stream of this solution with a stream of an aqueous inorganic base, allowing the aqueous and organic phases to settle after a suitable residence time, and phase separating the phases, all on a continuous basis. When using N-methyl-N-nitrosourea as the amine, the diazomethane process is preceded by a continuous nitrosation process involving combining aqueous solutions of methyl urea and a nitrite salt with an organic solution of a mineral or organic acid, the solvent in the organic solution being a mixture of the two organic solvents referred to above, allowing the aqueous and organic phases to settle after a suitable residence time, and phase separating the phases, all on a continuous basis. The resulting organic phase is continuously fed to the diazomethane stages described above.

A convenient synthesis of alkynylpyrazoles

Abstract: Diazomethane add to the enyne sulfones 1, 3, 4, 6–11 regio- and stereo-selectively to give the 4-alkynyl-5-phenylsulfonyl-4,5-dihydro-3H-pyrazoles 12–15 and 17–19, which are converted by MeLi into the 4-alkynyl-1H-pyrazoles 24, 25, 16, 26, 28, 30 in good yields. 4,5-Bis(alkynyl)-1H-pyrazoles 34, 37 are also obtained by the same procedure.

Triphenylphosphonio-Substituted 1,2,3,4-Triazaphospholes and 1,2,4-Diazaphospholes

Abstract: Several products resulting from the condensation of the bis-(trimethylsilyl)ylide 1 with PCl3 serve as synthetic equivalents of a phosphoniophosphaethyne. Cycloaddition reactions with azides lead to phosphonio-1,2,3,4-triazaphosphole cations 5, 7 and to the zwitterionic phosphonio-1,2,3,4-triazaphospholide 6. The latter readily undergoes a cycloreversion yielding a phosphoranediyl diazomethane 12 as intermediate. Its cycloaddition affords the diphosphonio-1,2,4-diazaphosholide chloride 9a as the final product. 9a is a remarkably stable and unreactive derivative of the two-coordinate phosphorus. By HCL it is protonated at a nitrogen atom to give dication without any tendency to associate with the chloride counterions.

Total synthesis of milbemycin E: resolution of the C(1)–C(10)fragment and final assembly

Abstract: The racemic hydroxycyclohexanone (±)-7, prepared by the Robinson addition of the keto ester 5 to 3-methylbut-3-enone 6, has been reduced stereoselectively to give the racemic cyclohexanediol (±)-8. This has been resolved by fractional crystallisation of the acetylmandelate esters 10 and 11. With (S)-acetyl mandelic acid 9, diastereoisomer 11 crystallises out. The required, dextrorotatory, enantiomer of the cyclohexanediol (±)-8 has been obtained by selective saponification of the mixture of the diastereoisomers 10 and 11, to give the mandelates 12 and 13, followed by crystallisation of the required diastereoisomer 12. Saponification of 12 gives the dextrorotatory enantiomer of the cyclohexanediol (+)-8 [which could alternatively have been obtained directly from the racemic diol (±)-8 using (R)-acetylmandelate ent-9]. Oxidation of the dextrorotatory diol (+)-8 gives the laevorotatory hydroxy ketone (-)-7. The 3,4-double bond has been introduced into this ketone by regioselective enol trimethylsilyl ether formation, phenylselanation and oxidative elimination, followed by reduction to give the cyclohexenediol 18. Methylation, saponification and re-esterification give the 2-furylcyclohexenoate 23, which on oxidation using singlet oxygen is converted into the hydroxybutenolide 3. The dextrorotatory diol (+)-8 has also been converted into the hydroxybutenolide 29 which lacks the 3,4-double bond. Conditions have been developed for the Wittig reactions between the hydroxybutenolides 29 and 3 and the phosphonium salt 2 to give the esters 32 and 37 after esterification using diazomethane and iodine induced isomerisation of the 10,11-double bond. Deprotection gives the hydroxy acids 33 and 39 which have been cyclised to give the macrolides 34 and 40. Selective reduction of these methyl esters gives 3,4-dihydromilbemycin E 35 and milbemycin E 1.

1-Allylgermatrane. Synthesis, Structure and Reaction with Diazomethane

Abstract: Reaction of allyltribromogermane (2), readily available from dibromo(1,4-dioxane)germanium(II) (1) and allylbromide, with tris(2-tributylstannoxyethyl)-amine (4) gives 1-allylgermatrane (3) in almost quantitative yield. 3 crystallizes from n-pentane as a colourless crystalline solid which was characterized by 1H and 13C NMR spectroscopy and by an X-ray crystal structure study. The “atrane” skeleton shows a strong conformational disorder; the Ge-N distance of 2.208(3) Å suggests the presence of a coordinative Ge-N bond. Treatment of 1-allylgermatrane (3) with CH2N2 in the presence of catalytic amounts of Pd(OAc)2 affords 1-cyclopropylmethylgermatrane (5) in high yield