Synthese von α-Methyl-homocysteinthiolacton

Summary A facile high yield large scale methylation procedure affording2c is reported utilizing the N-[bis(methylthio)-methylen-protected derivative4a as an intermediate. The optical resolution of racemic2c is described leading to (S)-2b. In addition the thiolactone2c undergoes oxidative ring opening by bromine to the corresponding sulphonic acid5.

     

Darzens reaction as a convenient method for the synthesis of α-chloroketones, α-chloroepoxides,and symmetrically substituted dioxines

Summary TheDarzens reaction of dichloroacetophenone (DCAP) with substituted benzaldehydes has been studied. The structure of the products was shown to depend on the phenyl group substituents. Reaction of benzaldehyde, 4-bromo-, and 2,4-dichlorobenzaldehydes results in 1-phenyl-3-aryl-3-chloropropane-1,2-diones (2a–c), reaction ofpara- ormeta-nitrobenzaldehydes yields 1-phenyl-2-chloro-3-aryl-2,3-epoxypropane-1-ones (3a, b). Upon the introduction of an alkoxy group into the phenyl ring of benzaldexyde and/or dichloroacetophenone, symmetrically substituted dioxines were obtained (6a–c). The structure of the reaction products has been established by single crystal X-ray investigations.

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Darzens-Reaktion als bequemes Verfahren zur Synthese von -Chloroketonen, -Chloroepoxiden und symmetrisch substituierten Dioxinen

Zusammenfassung DieDarzens-Reaction von Dichloracetophenon (DCAP) mit substituierten Benzaldehyden wurde untersucht. Die Struktur der Produkte ist von den Substituenten an der Phenylgruppe abhängig. Die Umsetzung mit Benzaldehyd, 4-Brom- und 2,4-Dichlorbenzaldehyd liefert 1-Phenyl-3-aryl-3-chloropropan-1,2-dione (2a–c), die Reaktion vonpara- odermeta-Nitrobenzaldehyd 1-Phenyl-2-chloro-3-aryl-2,3-epoxipropan-1-one (3a,b). Durch Einführung einer Alkoxygruppe in den Phenylring des Benzaldehyds und/oder des Dichloracetophenons erhält man symmetrisch substituierte Dioxine (6a–c). Die Struktur der Reaktionsprodukte wurde mittels Röntgenstrukturanalyse bestätigt.

     

Influence of the β-substitution on the photochemistry of α,2-diacetoxystyrenes. Irradiation of phenyl,vinyl, and benzyl derivatives

Summary -Substitution shows a pronounced influence on the photochemistry of ,2-diacetoxystyrenes. As in the case of the parent compound, intramolecular cyclization with participation of the neighbouring 2-acetoxy group takes place upon irradiation of the enol esters4a–c; however other processes are also observed, depending on the substrate. The phenyl derivative4a gives theE isomer7a and the phenanthrene9. The vinyl derivative4b also undergoescis-trans isomerization and/or photooxidation, to afford7b and10. Finally, a 1,4-acyl migration occurs in the benzyl derivative4c, whereby the 1,4-diketone12 is formed.

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Einfluß der -Substitution auf die Photochemie von ,2-Diacetoxystyrolen. Bestrahlung von Phenyl-, Vinyl- und Benzylderivaten

Zusammenfassung Bei ,2-Diacetoxystyrolen haben die -Substituenten einen deutlichen Einfluß auf das photochemische Verhalten. Wie im Fall der Stammverbindung erfolgt bei der Bestrahlung der Enolester4a–c intramoleukulare Cyclisierung unter Einbeziehung der benachbarten 2-Acetoxygruppe; jedoch werden je nach Substrat auch andere Reaktionen beobachtet. Das Phenylderivat4a liefert dasE-Isomer7a und das Phenanthren9. Das Vinylderivat4b erfährt ebenfallscis/trans-Isomerisierung zu7b und/oder Photooxidation zu10. Beim Benzylderivat4c tritt eine 1,4-Acylverschiebung zum 1,4-Diketon12 auf.

     

Aromatische Spirane. 15. Mitt. Darstellung von 2,2′-Spirobi-(s-hydrindacen)-1,1′-dion und von 4,4′-disubstituierten 2,2′-Spirobi-(s-hydrindacenen)

The title compound6 a was prepared by cyclisation of the diacid4 b. The diester4 a of4 b was synthesized by alkylation of2 with3 and following Retro-Claisen-reaction. After catalytic reduction of6 a to8 a two identical substituents were introduced byFriedel-Crafts-reaction (28). By transformation of the acetylgroups several other derivates (29–36) could be obtained. The unsymmetrical compounds (e.g.21) were prepared from20, whose precurser was the spiroketon10 a.

     

Syntheses with heterocyclic β-enaminonitriles: An expeditious synthetic approach to polyfunctionally substituted 5-phenylsulfonylthiophenes and their fused derivatives

Summary Phenylsulfonylacetophenones1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles2. Compound2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives3 and5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of5 to develop a facile convenient route to the polyfunctionally substituted thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidines8, 14, 17, 20, and21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.

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Synthesen mit heterocyclischen -Enaminonitrilen: Ein rascher synthetischer Zugang zu polyfunktionell substituierten 5-Phenylsulfonylthiophenen und ihren kondensierten Derivaten

Zusammenfassung Die Phenylsulfonylacetophenone1 reagieren mit einem Gemisch aus elementarem Schwefel und Malonsäurenitril zu den entsprechenden 2-Amino-4-aryl-5-phenylsulfonylthiophen-3-carbonitrilen2. Durch Umsetzung mit Stickstoffnucleophilen wie Cyanamid und Hydroxylaminhydrochlorid konnten aus Verbindung2a die entsprechenden Thieno[2,3-d]pyrimidin- und Thieno[2,3-c]pyrazolderivate erhalten werden. Das synthetische Potential und die Anwendbarkeit von5 zur Synthese polyfunktionell substituierter Thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidine (8,14,17,20,21) werden beschrieben. Die Strukturen der neuen Verbindungen wurden durch chemische und spektroskopische Methoden abgesichert.

     

Zur gezielten Oxidation der Δ7-Doppelbindung in den 4-Phenyl-1,2,4-triazolin-3,5-dion-Addukten des Vitamin D3

The possibility of regio- and stereospecific oxidation of the 7-double bond of the 4-phenyl-1,2,4-triazolin-3,5-dione adducts1 a and1 b of Vitamin D₃ is reported. Oxidation of the corresponding benzoates2 a and2 b withm-Chlorperbenzoic acid yields the two oxirans3 a and3 b which in turn with NaI-CH₃COOH-Zn after saponification to5 a and5 b lead to the allylic alcohols6 a and6 b.

     

Spectroscopic and quantum chemical investigation of enol-enol tautomerism of 2-acetyltetronic acid

Vibratonal spectra of 2-acetyltetronic acid (ATA) (3-acetyloxolane-2,4-dione) were investigated in different aggregate states.Ab initio quantum chemical calculations (3-21G basis set) of 2-formyltetronic acid as analogue of ATA and semi empirical calculation of ATA were carried out. The tautomeric forms of ATA can be arranged in the following series with respect to thermodynamic stability (in decresing order):1a,1b,2a,2b.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1043–1048, June, 1995.     

Heterocyclically bridged tricyclic β-lactames: A simple synthesis of 1,2,2a,8a-tetrahydro-3-oxa-1-aza-cyclobuta[b]naphthalen-2-ones

Summary The tricyclic 3,4-bridged -lactames7 and8 containing a hetero atom as 3-substituent of the azetidin-2-one ring were synthesized by intramolecular radical cyclization usingcis-substituted 3-(2-bromo-aryloxy)-azetidine-2-ones6 as precursors. These precursors were generated by stereospecific acid chloride-imine reaction from the corresponding substituted (2-bromophenoxy)-acetic acid chlorides2 and imine5.

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Heteroüberbrückte tricyclische -Lactame: Ein einfacher Zugang zu 1,2,2a,8a-Tetrahydro-3-oxa-1-aza-cyclobuta[b]naphthalin-2-onen

Zusammenfassung Die cis-substituierten 3-(2-Bromaryloxy)-azetidin-2-one6, dargestellt durch stereospezifische Säurechlorid/Imin-Reaktion aus den entsprechenden (2-Brom-phenoxy)-acetylchloriden2 und den Iminen5, reagieren im Zuge einer intramolekularen radikalischenexo-trig-Reaktion zu den 3,4-heteroüberbrückten tricyclischen -Lactamen7 und8.

     

Notiz zur [1,2]-Heterorest-Verschiebung in einem Sulfinamidin

Reaction of methyl 1-pyrroline-2-carboxylate (3 a) with N,N-Ditosylsulphur-diimide affords the pyrrol-2-carboxylic acid derivative7. The sulfenamide function in7 is cleaved by trimethyl phosphite leading to8. Presumably the reaction sequence (3 a 7) takes its course via the sulfinamidine4 a and the rearrangement product5 a followed by elimination of tosylamide. An analogous reaction starting with the dimethyl-1-pyrrolin-2-carboxylate3 b yields the stable sulfinamidine4 b, which undergoes a rearrangement reaction with base producing6 b with the thioaminal5 b as the intermediate.

Herrn Prof. Dr. Dr. h. c.K. Kratzl zum 70. Geburtstag herzlich gewidmet.     

Transformationen von β-Glycofuranosylisocyaniden in Tetrahydrofuranderivate

Summary Readily available -glycofuranosyl isocyanides1,2,4,5,6,18,19,20 are transformed into the corresponding protected tetrahydrofurans21,22,23,24,25,26 by means of tributyltin hydride andAIBN. The synthesis of18 and19 by dehydration of the formamide15 is described. Starting with 6-deoxy-1,2-O-isopropyliden--D-allofuranose (7) crystalline 1,2-O-diacetyl-3,5-dibenzoyl--D-allofuranose (9) is obtained.9 is first transformed into the anomeric azides11,12 and13,14 and subsequently into the formamide15.

     

Synthesis ofN-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids

The N-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids have been prepared for the first time by the interaction of ethyl 0-fltioroalkyl-,-dibromocarboxylates with primary amines.Prepared by a known procedure;² characteristics of previously unknown ester1b are given in the Experimental section.     

A novel synthesis of heterocycles from thiocarbohydrazides

Summary The reaction of thiocarbohydrazides1a and thiocarbazones1b with tetracyanoethylene (TCNE) afforded the thiazol, thiadiazole, thiazine, and thiadiazepine derivatives4–7. 2-Dicyanomethyleneindane-1,3-dione (CNIND) reacted with1a,b to give aminoindenopyrazolopyridazinone (12) and phenyl-1,2,3,4-tetraazacyclopentafluorene (13). The indazole and oxathiadiazole derivatives17 and19 were formed during the reaction of1b with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDO). 6,7-Dichloro-5-phenylpyrazolophthalazinol (21) was obtained from the reaction of1b with 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL-p). The oxidative cyclization of thiodicarbazones2a–d with the above acceptors afforded the thiadiazole and thiadiazine derivatives8 and10.

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Eine neue Synthese von Heterocyclen aus Thiocarbohydraziden

Zusammenfassung Die Reaktion der Thiocarbohydrazide1a und der Thiocarbazone1b mit Tetracyanoethylen (TCNE) ergab die Thiazol-, Thiadiazol-, Thiazin- und Thiadiazepinderivate4–7. 2-Dicyanomethylenindan-1,3-dion (CNIND) liefert mit1a,b Aminoindenopyrazolopyridazinon (12) und Phenyl-1,2,3,4-tetraazacyclopentafluoren (13). Die Indazol- und Oxathiadiazolderivate17 und19 wurden durch Reaktion von1b mit 1,3-Dichlor-5,6-dicyano-1,4-benzochinon (DDQ) gebildet. 6,7-Dichlor-5-phenylpyrazolophthalazinol (21) wurde aus1b und 2,3,5,6-Tetrachlor-1,4-benzochinon (CHL-p) erhalten. Die oxidative Cyclisierung der Thiodicarbazone2a–d mit den obengenannten Akzeptoren ergab die Thiadiazol- und Thiadiazinderivate8 und10.

     

Tetracyclische Imidazole

2-(Phenacyl)-tetrahydro--carboline (2) was transformed to theE/Z-oximes3 and4 and the isolated species cyclodehydrogenated to the nitrone5 and oxadiazine6. These compounds were dehydrated in acidic medium to the imidazole9.

     

Ein einfacher Zugang zu (R)-γ-Amino-β-hydroxybuttersäure (GABOB) aus natürlichem (2S, 4R)-4-Hydroxyprolin

The oxidative decarboxylation sequence (1a 2a 3a 4a 5a) affording -aminobutanoic acid (5a) is adapted to the synthesis of its hydroxy derivative5b. A facile high yield conversion of (2S, 4R)-4-hydroxyproline-methylester-hydrochloride (7) to (R)-GABOB (5b) on a preparative scale is reported with the hydroxypyrrolidone8 as the intermediate.

     

Sila-Riechstoffe und Riechstoffe-Isostere, 10. Mitt. Ein neuer Weg zu Sila-β-Jonon

Preparation of sila--ionone (14) was possible by a novel route with yields nearly 5 times higher than before¹, with the formerly unknown 1,1,3-trimethyl-1-silacyclohexanone-2 (6) as a key substance. The nine reaction steps may be seen from Scheme 1. 2-Ethinyl-1,1,3-trimethyl-1-silacyclohexan-2-ol (7) could not be dehydrated to give the analogous silacyclohexene derivative9. But dehydration was successful in the case of 2-(1-butin-3-ol) substituents; here only the ring but not the chain hydroxyl group was eliminated.

     

Synthesis of pyridine derivatives by reactions of α,β-unsaturated nitriles with 2-oxo-cycloalkano carbothioic acid anilides

Summary The tandem Michael addition-cyclization of 2-oxo-cycloalkane carbothioic acid anilides1–3 to benzylidenemalononitrile4 yielded spiroannulated pyridines5–7. Reaction of acrylonitrile with2 and3 gave 2,2-disubstituted Michael adducts14,15, whereas with1 led to 2,2,5-tri(2-cyanoethyl)-cyclopentanone11.

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Synthese von Pyridinderivaten durch Reaktionen von ,-ungesättigten Nitrilen mit 2-Oxo-cycloalkano-thiokohlensäure-aniliden

Zusammenfassung Die Michael Tandem-Addition-Cyclisierung von 2-Oxo-cycloalkano-thiokohlensäure-aniliden1–3 mit Benzylidenmalononitril4 ergab die spiroannelierten Pyridine5–7. Reaktion von Acrylnitril mit2 und3 ergab die 2,2-disubstituierten Michael-Addukte14,15, wohingegen mit1 2,2,5-Tri(2-cyanethyl)-cyclopentanon11 erhalten wurde.

     

Glykosylazide als Ausgangsbasis zur Gewinnung von Nucleosidanalogen, 3. Mitt. Synthese von Alkylaminotetrazol- und Uretidinonnucleosiden

The -ribofuranosylazide1 is transformed after usual derivatization by suitable protecting groups into the P–N-ylid2, which gives the corresponding N-Glykosyl-N-alkylcarbodiimides4 and a small amount of the glykosylisocyanatde-rivative3 by reaction with alkylisocyanates. The carbodiimides4 were reacted with hydrazoic acid to give the alkylaminotetrazolnucleosides5 and finally the free nucleosidanalogs6. In the case of5 c the 5-aziridinyltetrazolnucleosid5 h was formed by an usual neighbouring group reaction. In addition the compound1 is transformed into the 3,5-diprotected anchor derivative7 by reaction withTIPSCl₂. The latter could be transformed by usual steps into the alkylaminotetra-zolnucleosides8 with a free 2-OH group. In the next step the 2-p-tolylthiocarbo-nates9 were prepared followed by transformation to the 2-desoxynucleosides10 by means of tributyltinhydride. Finally the free 2-desoxynucleosides11 were prepared. By reacting the carbodiimides4 with phenylisocyanate a mixture of the two possible regiouretidinonnucleosidderivatives12 and13 are formed. In the case of the N-glykosyl-N-allylcarbodiimide4 d only the one isomer13 d arises.

Herrn Prof. Dr.A. Neckel mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Condensation of 1-Substituted 5-Aminopyrazoles with β-Dicarbonyl Compounds

Condensation of N-substituted 5-aminopyrazoles with -diketones occurs with the formation of pyrazolo[4,5-b]pyridines. Depending on the conditions, their reaction with -keto acids can give either 6-oxo- or 4-oxopyrazolo[4,5-b]pyridines.     

Hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propenenitriles with enol ethers. Synthesis of 2-alkoxy-3,4-dihydro-2H-pyran-5-carbonitriles

Summary The hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propenenitriles1a–d with enol ethers2a–c yieldscis/trans diastereoisomers of 2-alkoxy-4,6-diaryl-3,4-dihydro-2H-pyran-5-carbonitriles3 and4 in 79–98% yield. The similar reaction of1a–c with cyclic enol ether5 affords diastereoisomeric cycloadducts6 and7 withcis annulated pyran rings. Reaction of3 with sulfuric acid leads to 2-hydroxy-3,4-dihydro-2H-pyran-5-carbonitriles8 and9.

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Hetero-Diels-Alder-Reaktion von 3-Aryl-2-benzoyl-2-propennitrilen mit Enolethern. Synthese von 2-Alkoxy-3,4-dihydro-2H-pyran-5-nitrilen

Zusammenfassung Die Hetero-Diels-Alder-Reaktion der 3-Aryl-2-benzoyl-2-propennitrile1a–d mit den Enolethern2a–c ergibt diecis/trans-diastereomeren 2-Alkoxy-4,6-diaryl-3,4-dihydro-2H-pyran-5-nitrile3 und4 in einer Ausbeute von 79–98%. Dieselbe Reaktion von1a–c mit dem cyclischen Enolether5 liefert die diastereomeren Cycloaddukte6 und7 mitcis-anellierten Pyranringen. Reaktion von3 mit Schwefelsäure führt zu den 2-Hydroxy-3,4-dihydro-2H-pyran-5-nitrilen8 und9.

     

Über die Reaktionen von monosubstituierten Guanidinen mit α,β-ungesättigten Ketonen

Action of methyl-, benzyl- and phenylguanidine on mesityloxide yields the 2-R ³-imino-4,4,6-trimethyl-1,2,3,4-tetrahydropyrimidines resp. 2-R³-aminopyrimidines8 b, c ande, cyclohexylidenacetone reacts with benzylguanidine to give the 2-benzylimino-4-methyl-1,3-diazaspiro[5.5]undeca-4-en resp. the benzylaminodiazaspiroundecadien (8 d). The isomeric 1- and 3-R³-pyrimidinimines (resp.-amines)9 b-e and10 b-e are not formed in the reaction. The structures were proved by spectroscopical and chemical methods.

Herrn Prof. Dr.G. Zigeuner zum 60. Geburtstag gewidmet.