Thermische Lactonisierung von Estern γ-Brom-α, β-ungesättigter Carbonsäuren zu Δα-Butenoliden. Direkte γ-Bromierung von α, β-ungesättigten Säuren

By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ^7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δ^α-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δ^α-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δ^α-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δ^α-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δ^α-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δ^α-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δ^α-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.     

Die 1,3-dipolare Cycloaddition von Acetylendicarbonsäure-estern an 2-Methyl-4-phenyl-chinazolin-3-oxid

The 1,3-dipolar addition of acetylenedicarboxylic esters (IX and X) to 2-methyl-4-phenyl-quinazoline 3-oxide (VIII) in benzene/methanol and benzene/ethanol, respectively, gives the esters XI and XII of 3-amino-3-phenyl-2-(2-acetamidophenyl)-acrylic acid as main products and the esters XIII and XIV of 2-methyl-4-phenyl-5H-benzo[d][1,3]diazepin-5-carboxylic acid as by-products. The constitutions of XI and XII are elucidated by acid hydrolysis to the 2-phenylindole-3-carboxylic esters VI and VII, respectively, and by ozonolysis of XII to give benzamide and ethyl o-acetamido-mandelate (IV). The alkaline hydrolysis of XI or XII gives the enamine derivative XVIII, which is hydrolysed by acid to oxindole and benzoic acid. The structure elucidation of XIII and XIV is based on spectroscopic data together with thc formation of XV by alkaline hydrolysis. Mechanisms arc proposed for the reaction paths.     

Arbeiten über Phosphorsäure- und Thiophosphorsäureester mit einem heterocyclischen Substituenten. 7. Mitteilung. Thio- und Dithiophosphorsäureester von der Art des GS 13005 mit einem analogen oder homologen heterocyclischen Ring

To complete results presented in this and in previous papers of this series as well as published in patents of other authors a review is given on known and new variations of the heterocyclic moiety in GS 13005 type thio- and dithiophosphoric acid esters ( 1, 2 ) by modification of the 1,3,4-thiadiazol-2(3H)-one ring 5 and by its replacement by analogue five- and homologue six-membered rings. Among new esters of this type some containing the pyrazolinone ring 3 or a 2-alkoxy-4H, 6H-1,3,4-thiadiazin-5-one ring 10 (homologue of the original 5-methoxy-1,3,4-thiadiazol-2(3H)-one ring in GS 13005) show no remarkable pesticidal activity, some others containing a pyrazolering 7 or a 3(2H)-pyridazinonc ring 8 are moderately to highly active but toxic to inauinials in the same proportion. Attempts to prepare seven-membered 2-alkoxy- and 2-alkylthio-6,7-dihydro-l, 3,4-thiadiazepin-S(4H)-ones 11 , Z-rnethoxy-l,3,4-thiadiazepin-S(4H)-one 12 (ring vinylogue of the original 5-methoxy-l,3,4-thiadIazol-2(3H)-one ring in GS 13005) and its 7-methyl-derivative have been unsuccessful due to unexpected side reactions, such as: five-ring closure of 3-(3-chloropropionyl)-thio- and -dithiocarbazic acid esters 22 to pyrazolidinone derivatives 23 , pyrazolinone ring closure of a 3-(acetoacety1)-thiocarbazic acid O-methyl ester derivative 26 , bromine attack on sulfur in 3-(2-alkenoyl)-thiocarbazic O-methyl esters 29 instead of bromine addition at the double bond, and halogen splitting off without ring closure in 3-(2,3-dihalogeno-alkanoyl) -thiocarbazic O-methyl esters 30 prepared by acylation of thiocarbazic acid O-methyl ester with dihalogeno-alkanoyl-chlorides.     

Vergleich der Produkte aus der Reaktion von Phenylguanidin-Derivaten mit β-Ketoestern bzw. Propiolsäureestern (Synthese von Pyrimidonen)

Comparison of reaction products afforded by phenylguanidine derivatives with β-ketoesters or propiolic esters, respectively (synthesis of pyrimidones). 2-Anilino-imidazolines, when treated with either β-ketoesters or propiolic esters, yield two isomeric groups of pyrimidones. The isomerism is based on different positions of the carbonyl group in the pyrimidone ring. The mass spectra permit an unequivocal assignment of constitution I to the product formed with β-ketoesters and of constitution V to that formed with propiolic esters. Additionally, 2-(2-amino-anilino)-2-imidazoline (XII) when treated with methyl phenylpropiolate yields IX; while treatment with ethyl benzoylacetate yields XIII as an intermediate, which eliminates spontaneously one molecule of water to give the benzimidazole derivative XIV. Phenylguanidines (XV) add propiolic esters in the same way as do imidazoline derivatives. Photochemical cleavage of two carbon atoms with their adherent hydrogen atoms from the imidazole ring of the pyrimidones (V) leads to aminopyrimidine derivatives, e.g. XVI.     

Synthese und Reaktionen von Bicyclo[6.4.0]dodecan-3-carbonsäure-Derivaten

Synthesis and Reactions of the Bicyclo[6.4.0]dodecane-3-carboxylic Acid Derivatives The synthesis and some consecutive reactions of the compounds 5-8 , derivatives of bicyclo[6.4.0]dodecane-3-carboxylic acid ( 1 ), are described. The esters 7 and 8 can be obtained by Baeyer-Villiger oxidation of 2-hydroxy-8-methyltricyclo[7.3.1.0^2,7]tridecan-13-one ( 4 ) and subsequent hydrolysis of the lactone 5 . The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D-NMR methods). The formation of 7 via 1,2-H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8 .     

Bortrifluorid-katalysierte Umsetzungen von 3-Amino-2H-azirinen mit Aminosäure-estern und Aminen

Boron-Trifluoride-Catalyzed Reactions of 3-Amino-2H-azirines with Amino-acid Esters and Amines After activation by protonation or complexation with BF₃, 3-amino-2H-azirines 1 react with the amino group of α-amino-acid esters 3 to give 3,6-dihydro-5-aminopyrazin-2(1H)-ones 4 by ring enlargement (Scheme 2, Table 1). The configuration of 3 is retained in the products 4 . With unsymmetrically substituted 1 (R¹ ≠ R²), two diastereoisomers of 4 (cis and trans) are formed in a ratio of 1:1 to 2:1. With β-amino-acid esters 5 and 7 , only openchain α-amino-imidamides 6 and 8 , respectively, are formed, but none of the seven-membered heterocycle (Scheme 3). Primary amines also react with BF₃-complexed 1 to yield α-amino-imidamides of type 9 (Scheme 4, Table 2). Compound 9b is characterized chemically by its transformation into crystalline derivatives 10 and 12 with 4-nitrobenzoyl chloride and phenyl isothiocyanate, respectively (Scheme 5). The structure of 12 is established by X-ray crystallography. Mechanisms for the reaction of activated 1 with amino groups are proposed in Schemes 6 and 7.     

Neue β-Lactam-Antibiotika. Zur Funktionalisierung von 3-Hydroxy-3-cephem-4-carbonsäureestern durch die Wittig-Reaktion. Modifikationen von Antibiotika. 16. Mitteilung [1]

New β-lactam antibiotics. Functionalisation of 3-hydroxy-3-cephem-4-carboxylic esters through the Wittig reaction The 3-hydroxy-ceph-3-em-esters 1a, b reacted smoothly with stabilized phosphor-ylids to give a series of derivatives which were converted into the microbiologically active acids 14a, c, 15c and 20 by known procedures. The synthesis of the amides 23, 24, 26 and of the ester 28 from the 3-carboxymethyl-derivative 19 is also reported.     

Reaction of the Reformatskii reagent obtained from bromotetrahydrofuran-2-one with 2-oxochromene-3-carboxylic or 3-oxo-3<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">f</Emphasis>]chromene-2-carboxylic acid derivatives

The Reformatskii reagent obtained from 3-bromotetrahydrofuran-2-one reacts with alkyl esters of 6-bromo- and 6,8-dibromo-2-oxochromene-3-carboxylic acid or alkyl esters and N-benzylamide of 3-oxo-3H-benzo[f]chromene-2-carboxylic acid to form alkyl esters of 6-bromo- and 6,8-dibromo-2-oxo-4-(2-oxotetrahydrofuran-3-yl)chroman-3-carboxylic acid or alkyl esters and N-benzylamide of 2,3- dihydro-3-oxo-1-(2-oxotetrahdrofuran-3-yl)-1H-benzo[f]chromene-2-carboxylic acid as a mixture of two diastereomers.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1513–1515.Original Russian Text Copyright © 2004 by Shchepin, Fotin, Shurov.This revised version was published online in April 2005 with a corrected cover date.     

Rhodium-Katalysierte Isomerisierungen von 2-Methylidenglutarsäureestern zu Methylglutaconsäureestern

The Rhodium(III)-catalyzed thermal isomerization of 2-methylidenglutaric acid esters affords predominantly mixtures of cis/trans-2-methylglutaconic acid esters ( 2, 3 ) which upon slow distillation isomerize completely into the cis-esters ( 2 ). Saponification of 2 yields trans-2-methylglutaconic acid ( 5 ). Attempts to prepare the acid chloride of 5 produces 6-chloro-5-methylpyrone-2 ( 9 ) or 6-chloro-3-methylpyrone-2 ( 10 ) which react with anilines to N-substituted derivatives of trans-4-methylglutaconic acid amides ( 11 ). The thermal isomerizations of the respective esters are discussed in terms of 1,5-hydrogen shifts in their ester enol structures.     

Les β-cétonitriles groupes protecteurs de la fonction amine. Préparation d'amino-alcools

β-Ketonitrile-Derived Protecting Groups of the Amino Function. Synthesis of Amino Alcohols The amino group of natural L -amino acid esters is protected by condensation with 2-oxocyclopentanenitrile ( 1 ) or 2-formyl-2-phenylacetonitrile ( 10 ). Only the ester group of the formed cyanoenamino esters 2 and 11 reacts with nucleophilic reagents such as organometallics (RMgX, RLi), borohydrides, or metal amides, whereas the cyanoenamino group is unchanged (Schemes 1 and 2). Cyanoenamino alcohols obtained by reduction of cyanoenamino esters 2 are hydrolyzed under acidic conditions to amino alcohols with retention of the configuration of the starting amino acid. This sequence of reactions allows to prepare derivatives of L -tyrosinol from (?)-L -tyrosine (see, e.g., Scheme 4). Cyanoenamino esters 11 are readily methylated at the N-atom to give N-methylated cyanoenamino esters (Scheme 3). This property is exploited on the way of a multistep procedure to obtain N-methylated amino alcohols homologous to natural (?)-(1R,2S)-ephedrine.     

Photoinduzierte Reaktionen von 3-Phenyl-2H-azirinen mit Carbonsäureestern 40. Mitteilung über Photoreaktionen

Irradiation (280–350 nm light) of a benzene solution of 3-phenyl-2H-azirines 1a – e in the presence of carboxylate esters, whose carbonyl groups are activated by electron withdrawing groups situated in the acyl or alkyl moiety, produces 5-alkoxy-3-oxazolines (Tab. 1 and 4, Scheme 2) isolated in 18–82% yield. These heterocycles undoubtedly originate by regiospecific addition of the ester carbonyl group to the azirine-derived benzonitrile-methylide ‘dipole’ (Scheme 1). The 5-(2,′ 2′, 2′-trifluoroethoxy)-3-oxazolines, derived from 2′, 2′, 2′-trifluoroethyl carboxylic esters, on treatment with methanolic hydrogen chloride at low concentration, are smoothly transformed into the corresponding 5-methoxy-3-oxazolines (e.g. 16 → 17 , Tab. 5). Utilizing this process, various hitherto relatively unknown 9. 5-alkoxy-3-oxazolines become accessible. The constitution of the adducts is based essentially on spectral data. The structure of trans-5-methoxy-2,4-diphenyl-5-trifluoromethyl-3-oxazoline (trans- 14 ), the addition product of methyl trifluoroacetate and the benzonitrile-benzylide from 2,3-diphenyl-2H-azirine ( 1d ), was determined by X-ray crystallography (Section 5). Benzonitrile-isopropylide ( 22 ), resulting from the photochemical transformation of 2,2-dimethyl-3-phenyl-2H-azirine ( 1a ), also reacts with S-methyl thiobenzoate to give 2,2-dimethyl-5-methylthio-4,5-diphenyl-3-oxazoline ( 26 ). Ethyl cyanoacetate protonates predominantly the dipolar species derived from 1a at the nitrile C-atom and yields after work-up ethyl α-cyano-cinnamate ( 29 ) and ethyl isopropylidene-cyanoacetate ( 30 ) (Scheme 4). The relative rate of addition (k_rel) of benzonitrile-isopropylide ( 22 ) to methyl α-haloacetates and dimethyl oxalate was determined by competition experiments (Section 6). Log k_rel correlated satisfactorily (r = 0.97) with the pK_a of the acide derived from the ester reactant: log k_rel = ? 1.72 pK_a + 2.58 or with Taft's substituent constants σ*: log k_rel = 2.06 σ* ? 4.11 [k_rel(methyl dichloroacetate) = 1; Section 7.1]. On the basis of the results obtained, the mode of reaction of the so-called benzonitrile-methylide ‘dipole’ is discussed and a model for the transition state of addition of ester-carbonyl groups is proposed that accounts for the observed regiospecifity and steroselectivity.     

Über die Konstitution von Loroglossin. Vorläufige Mitteilung

The Constitution of Loroglossine. Loroglossine, a characteristic constituent of orchids, is shown to be bis-[4-(β-D -glucopyranosyloxy)-benzyl]-(2 R, 3 S)-2-isobutyl-tartrate ( 1 ). Hydrolysis and esterification gave 1 mol-equiv. of dimethyl (+)-2-isobutyl-erythro-tartrate ((+)-3) and 2 mol.-equiv. of a glucoside which, after acetylation, gave 4 , identical with a synthetic sample. The erythro configuration of (+)- 3 by oxidation of isobutyl-maleic acid with osmium tetroxide and subsequent esterification. The absolute configuration of (+)- 3 was based on Horeau experiments and NMR. data of the diastereomeric mixture of its esters 7 and 8 with S (+)- and R (?)-α-phenylbutyric acid respectively.     

1H-NMR.-spektroskopische Analyse von prochiralen Allencarbonsäureestern mit optisch aktiven Europium-Verschiebungsreagenzien

¹H-NMR. Spectroscopic Analysis of Prochiral Allenic Esters Using Optically Active Europium Shift Reagents The prochiral allenic methyl esters 1–4 (cf. Scheme) show in the presence of 1 mol-equiv. tris[3-(heptafluorobutyryl)-(+)-camphorato]europium (III) (Eu (hfc)₃) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) induced unlike ¹H-NMR. shift differences (ΔΔδ) for the enantiotopic protons and methyl groups on C(4), respectively (cf. Fig. 2 and 3). This effect allows to determine directly the ²J_H,H coupling constants of the geminal protons on C(4) of the allenic esters 1 (15.5 Hz) and 2 (14.5 Hz) (cf. Table 2).     

Nucleophile Addition von Triorganozinn-Anionen an Kohlenstoffdisulfid. IV. Darstellung und Komplexbildung von 1,n-Bis(triphenylstannandithiocarbonsäure)alkylenestern

Nucleophilic Addition of Triorganotin Anions to Carbon Disulfide. IV. Synthesis and Complex Formation of 1,n-Bis(triphenylstannanedithiocarboxylic) Alkylene Esters The reaction of lithium triphenylstannanedithiocarboxylate with 1,n-dibromo-alkanes in THF solution yields for 3 ? n ? 6 stable 1,n-bis(triphenylstannanedithiocarboxylic) alkylene esters I–IV whereas for n = 1,2 elimination takes place. Only the propylene and butylene esters I, II (L) form with irradiated metal carbonyls neutral dinuclear complexes of the type M? L? M (M = W(CO)₅, CpMn(CO)₂) with monodentate coordination of the thiocarbonyl group on each side. Since the esters I–IV preferably adopt the open n-alkane conformation, no formation of a chelate ring occurs from steric reasons.     

Synthese von racemischen,isomeren Desoxo-4, 14-didemethyl-cassain-Derivaten. 4. Mitteilung über Cassain-Analoga

For the synthesis of demethyl analogues of Erythrophleum alkaloids, the tricyclic ketone 14 (trans-anti-trans) was prepared. The Horner reaction on 14 led to a mixture of cis/trans compounds, which could be separated into the homogeneous racemic isomers 21 and 22 . These compounds were transformed into the corresponding 2-dimethylamino-ethyl esters of their 3-dehydro and 3-O-carbamoyl derivatives.     

Chinazolincarbonsäuren. VII. Mitteilung. Ein einfacher Zugang zu (4-Oxo-3,4-dihydrochinazolin-3-yl)-alkansäuren, (4-Oxo-3,4-dihydro-1,2,3-benzotriazin-3-yl)-alkansäuren und deren Estern

Quinazoline Carboxylic Acids. An Easy Route to (4-Oxo-3,4-dihydroquinazolin-3-yl)-alkanoic Acids, (4-Oxo-3,4-dihydro-1,2,3-benzotriazin-3-yl)-alkanoic Acids and their Esters A new route was found for the synthesis of (4-Oxo-3,4-dihydroquinazolin-3-yl)-alkanoic acids ( 8 ) and (4-Oxo-3,4-dihydro-1,2,3-benzotriazin-3-yl)-alkanoic acids ( 6 ) by cyclization of the N-(2-aminobenzoyl)amino acids 5 with HCOOH or HNO₂. 2H-3,1-Benzoxazine-2,4(1H)-diones ( 1 ) reacted with glycine esters to 2 , which were cyclized by HNO₂ to the esters 4 . Ester 4 was hydrolyzed to 6 (X = CH₂). Diones 1 reacted with the most common amino acids (as the ammonium salt of tertiary amine) to amino-alkanoic acids 5 , which were cyclized with orthoformate to 7 or 8 depending on the reaction conditions.     

Functional polymers. XLVII. Synthesis of various derivatives of ω-alkenoates

A number of derivatives of ω-alkenoates were synthesized in preparation for the synthesis of functional polymers based on α-olefins. For the preparation of most of the methyl esters, the regular esterification of ω-alkenoic acids, specifically 10-undecenoic acid with methanol and sulfuric acid as the catalyst, was most effective. For the preparation of the tert-butyl- and 2-ethylhexyl esters of 10-undecenoic acid, the acid chloride route was found to be most convenient, whereas for the preparation of the corresponding esters of 5-hexenoic acid, our method of choice was the synthesis via the imidazolyl derivative of the acid. 2,2,2-Trifluoroethyl 10-undecenoate and the 2,2-dimethyloxazolidine derivative of 10-undecenoic acid were prepared from the acid and 2,2,2-trifluoroethanol or 2-amino-2-methyl-propanol with p-toluene sulfonic acid as the catalyst. Esters of phenol, 2,6-dimethylphenol, and 2,6-diphenylphenol were synthesized from 3-butenoic and 10-undecenoic acid with trifluoroacetic anhydride.     

A simple route to syn α-Amino-β-Hydroxy esters by C-2 regioselective opening of a, β-Epoxy esters with metal halides

α,β-Epoxy esters are opened by NaX (X = I, Br) in a regio and stereoselective fashion to β-hydroxy-α-halo esters, which represent suitable precursors of syn α-amino-β-hydroxy esters and β-hydroxy esters.     

1H-NMR.-spektroskopische Bestimmung der Enantiomerenreinheit von Allencarbonsäureestern mit optisch aktiven Europium-Verschiebungsreagenzien

¹H-NMR. Spectroscopic Determination of Enantiomeric Purities of Allenic Esters Using Optically Active Europium Shift Reagents The racemic allenic methyl esters 3--7 and the racemic allenic diesters 8--10 (cf. Scheme 2) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) and CCl₄ in the presence of optically active tris[3-(heptafluorobutyryl)-(+)-camphorato]europium(III) (Eu(hfc)₃) have induced unlike ¹H-NMR. shift differences (ΔΔδ) for the protons of the methoxycarbonyl groups of their enantiomers. In some allenic esters the shift reagent causes additional separation of resonance signals; thus, further substituents on the allenic framework may be differentiated in the racemic mixture. This finding provides a widely applicable method for the determination of absolute enantiomeric purities of allenic esters and their corresponding acids. Accordingly we found for optically pure (+)-(S)-2-methyl-2,3-pentadienoic acid ((+)-(S)- 13 ; cf. Fig. 2) a calculated [α] value of + 73.3 ± 1.8°. Finally, the substituent effects on ΔΔδ-values (cf. Table 1--3) are discussed.     

Catalytic Asymmetric Epoxidation of α,β‐Unsaturated Esters with Chiral Yttrium–Biaryldiol Complexes

The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)₃–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)₃–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent.