Acid hydrolysis of amides obtained by Beckmann rearrangement of methyl ketones oximes of unsaturated γ-lactone,aromatic, and alicyclic series

Beckmann rearrangement was performed of oximes of substituted 3-acetyl-4-methyl-5,5-dimethyl(pentamethylene)-2-oxo-2,5-dihydrofuranes in the presence of boron trifluoride etherate. Aiming at establishing the spatial arrangement of the oximes the hydrolysis was carried out of acid amides obtained by Beckmann rearrangement of oximes of methyl ketones belonging to unsaturated γ-lactone series and also to aromatic and alicyclic series. The hydrolysis with 20% sulfuric acid led to the formation of the corresponding acid and amine, and the hydrolysis with acetic and hydrochloric acids resulted in retrobeckmann rearrangement giving the initial oximes.     

Reactions of acyloxiranes with aliphatic ketones

Acyloxiranes react with aliphatic ketones in the presence of boron trifluoride etherate to give the corresponding 4-acyl-1,3-dioxolanes. The corresponding 4,5s-dimethyl-4r-acetyl-1,3-dioxolanes are formed in this case from 2,3t-dimethyl-2r-acetyloxirane, whereas a mixture of cis- and trans-1,3-dioxolanes is formed from trans-2-acetyl-3-phenyloxirane and acetone. The reaction of acyloxiranes with unsymmetrical ketones gives a mixture of the cis- and trans-1,3-dioxolanes with respect to the substituents attached to C-2 relative to the acetyl group, whereas the isomer ratio in this case depends on the effective volumes of the substituents attached to C-2.     

Protonation studies on the oximes of some 7-acetyl-1,2-benzisothiazoles

Three 7-acetyl-1,2-benzisothiazoles have been made by cyclisation of the monooximes of 2-methylthio-1,3-diacetylbenzenes. The oximes of these ketones dissolved in acidic media give only protonated forms, and no indication of the formation of stable bridged sulfonium ions.     

A new and efficient method for conjugate addition of trialkylphosphites to 3-acylsubstituted coumarins

A new and efficient conjugate addition of trialkylphosphites to 3-ω-bromoacetylcoumarin 1 catalysed by p-toluenesulfonic acid (TsOH) has been studied. Under the same conditions, an enolphosphate gave the corresponding esters of 3-acetyl-4-phosphono-2-oxochromans in high yields. The use of TsOH in the reaction of 3-acetyl-, 3-benzoyl-, and 3-ethoxycarbonyl coumarins led mainly to 1,4-addition products—the corresponding 3-acyl-4-dialkylphosphono-2-oxochromans—in very good yields.     

A general method for the synthesis of the most powerful naturally occurring Maillard flavors

The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO₂ oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported.     

Synthesis of 5-Formyl and 5-Acyl-1,2-dithiole-3-ones

The preparation of new 5-formyl-, 5-acetyl- and 5-propionyl-1,2-dithiole-3-ones by oxidation of the corresponding 1,2-dithiole-3-thiones with mercuric acetate is described.     

1,2,4-Triazines in Organic Synthesis. 9. Synthesis of 3-(3-Ethylindol-2-yl)-5,6,7,8-tetrahydroisoquinoline Using the Fischer Reaction under the Usual Conditions and with Microwave Irradiation

The nucleophilic substitution of hydrogen in 3-methylthio-1,2,4-triazine by the carbanions of nitrobutane and 4-nitrobut-1-ene gave oximes, the selective fission of which using sodium dithionite gave ketones in the case of compounds with a saturated carbon chain. Ketones in Diels-Alder reaction with 1-pyrrolidinocyclohex-1-ene gave 3-acyl-1-methylthio-5,6,7,8-tetrahydroisoquinolines. Phenylhydrazones of the compounds obtained underwent Fischer reaction under usual conditions and also when using microwave irradiation on a solid support. The final 3-(3-ethylindol-2-yl)-5,6,7,8-tetrahydroisoquinoline was obtained via reductive desulfuration using Raney nickel in ethanol.     

Recyclization and photorearrangements of 2-acetyl-4,4-dialkyl-2-buten-4-olide oximes

Recyclization to derivatives of dihydro-1,2-oxazines was realized by the reaction of 2-acetyl-3-methyl-4,4-dialkyl-2-buten-4-olide oximes with sodium borohydride. The UV-irradiation-initiated Beckmann rearrangement of the oximes cited above leads to 4,4-dialkyl-2-buten-4-olide-2-carboxylic acid N-methylamides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 157–160, February, 1989.     

Regioselective Synthesis of 4-Acetyl-and 5-Acetyl-3-methylisoxazole: Their Conversion into Silyl-and Methyl Enol Ethers

Acetonitrile oxide reacts regioselectively with 3-buten-2-one and (E)-4-methoxy-3-buten-2-one to give 5-acetyl-2 and 4-acetyl-3-methylisoxazole 3, respectively. Treatment of ketones 2 and 3 with trimethylsilyl trifluoromethanesulfonate gave the silyl enol ethers 4 and 5, whereas the methyl enol ethers 8 and 9 were obtained via elimination of methanol from the corresponding dimethyl ketals.     

Zur Kenntnis der Substitutionsprodukte der (2H)-Imidazol-4(3H)-thione und 2H-Imidazol-4(3H)-one

2H-Imidazole-4(3H)-thiones (a), available from methyl alkyl and methyl aryl ketones with sulfur and ammonia, react via their corresponding N-sodium compounds or in presence of tert. amines with alkyl and aryl carboxylic acid chlorides to give the corresponding intensely coloured (orange to violett) cryst. 3-acyl-2H-imidazole-4(3H)-thiones4 a-q and6–26. With dicarboxylic acid dichlorides the colourless cryst. N,N′-diacyl-bis-3-imidazoline-5-thiones5 a-d and27–32 are obtained. With carbamic acid chlorides and chloroformic acid esters the corresponding urea (33–35) and urethane derivatives36, 37 are formed. In an analogous way 2H-imidazol-4(3H)-ones react with acid chlorides to 3-acyl-2-imidazol-4(3H)-ones (44–50), which can also be obtained by treating the corresponding 3-acyl-2H-imidazole-4(3H)-thione with KMnO₄.     

Synthesis of derivatives of 5-amino-4-acyl-1,2,3-triazole, 8-azapurine,and 1,2,3-triazolo[4,5-b]pyridin-7-one using N,N-acetals of acylketenes and tosylazide

By reaction of N,N-acetals of acylketenes with tosylazide there were synthesized 5-amino-4-acyl-1,2,3-triazoles substituted at the endo(N¹)- or exocyclic nitrogen atom. Triazoles containing a free NH₂ group were used in the synthesis of the corresponding 8-azapurines and 4-acetyl-5-benzoylamino-1,2,3-triazole afforded 2-methyl-2H,4H-1,2,3-triazolo[4,5-b]pyridin-7-one.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1392–1397, June, 1990.     

Synthesis,structure and cytotoxic activity of 2‐acetyl‐5‐trimethylsilylthiophene(furan) and their oximes

5‐Trimethylsilylderivatives of 2‐acetylthiophene and ‐furan have been regioselectively prepared by a one‐pot procedure from the corresponding 2‐acetylfuran or 2‐acetylthiophene using lithium N‐methylpiperazide (LNMP)–butyllithium–trimethylchlorosilane–water as the sequence of reagents. The ketones obtained were converted to the corresponding oximes. The structure of 2‐acetyl‐5‐trimethylsilylthiophene oxime (E‐isomer) has been studied by X‐ray diffraction. Formation of centrosymmetric dimers by means of H‐bonds has been observed. The intermolecular hydrogen bond O9? H…N8 length is 2.842(5) Å [H…N8 = 1.87 (6) Å, O9? H…N8 = 157(4)°]. Copyright © 2006 John Wiley & Sons, Ltd.     

Spiro-fused (C2)-azirino-(C4)-pyrazolones, a new heterocyclic system. Synthesis, spectroscopic studies and X-ray structure analysis

Reaction of 1-substituted 4-acyl-5-hydroxy-3-methyl-1H-pyrazoles (2) with hydroxylamine gives the corresponding "oximes" 3, which are mainly present as (Z)-2,4-dihydro-4-[(hydroxyamino)methylene]-3H-pyrazol-3-ones. Treatment of compounds 3 with trichloroacetyl isocyanate/potassium carbonate in anhydrous diethyl ether affords 7-methyl-1,5,6-triazaspiro[2.4]hepta-1,6-dien-4-ones (4). The structure of compounds 4 was elucidated by means of single-crystal X-ray analysis (4f, 4h) and confirmed by NMR spectroscopic investigations ((1)H, (13)C).     

Highly regioselective and practical synthesis of 1-acyl-5-hydroxypyrazolines and 1-acyl pyrazoles from 1,2-allenic ketones and hydrazides

A mild and highly regioselective synthesis of 1-acyl-5-hydroxypyrazolines has been achieved through the condensation of 1,2-allenic ketones with hydrazides in the absence of any catalyst. Moreover, the obtained 1-acyl-5-hydroxypyrazolines can be easily transformed into 1-acyl pyrazoles under the promotion of BF₃·Et₂O. It was also found that 1-acyl pyrazoles can be produced directly from allenic ketones and hydrazides through a one-pot procedure.     

Oxidative nucleophilic substitution of hydrogen versus ring-opening in the reaction of 4-R-2-nitrothiophenes with amines. The crucial effect of 4-alkyl groups

4-Alkyl-2-nitrothiophenes [10: R = CH3, CH(OH)CH3, CH(OCH3)CH3] react with secondary aliphatic amines, in the presence of AgNO3, to give 3-alkyl-2-amino-5-nitrothiophenes (12) through an oxidative nucleophilic substitution of hydrogen (ONSH) of synthetic interest. This behavior is in striking contrast with that of the parent 2-nitrothiophene (6), which was found to undergo ring-opening in analogous reaction conditions. A possible rationale for the crucial effect of alkyl groups is suggested, grounded also on a study of the corresponding Meisenheimer-like adducts.     

Synthesis of isomeric 4- and 5-hydroxylaminothiazolidin-2-thiones

Tsomeric 4- and 5-hydroxylaminothiazolidin-2-thiones were synthesized by the reaction of 1,2-aminosubstituted oximes with CS₂, and of dimeric olefin nitrosochlorides with dithiocarbamate salts. These compounds react with aldehydes and ketones to form the respective nitrones. In contrast to the 5-derivatives, the 4-hydroxylamino derivatives hydrolyze to 4-hydorxythiazolidin-2-thiones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 549–553, April, 1986.     

Formation of bishomoazasteroids by the beckmann rearrangement

Beckmann rearrangement of the geometrical isomer of 5α-androstanolone oximes gives the 3-aza-17β-hydroxy-A-homo-5α-androstan-4-one and the 4-aza-17β-hydroxy-A-homo-5α-androstan-3-one. These lactams were converted to the corresponding ketones by Jones reagent oxidation. Treatment with hydroxylamine produced the corresponding ketoximes. Beckmann rearrangement of the ketoximes generated the diaza compounds and the corresponding “second order” Beckmann cleavage ω-cyanoolefin. The mixture of the compounds produced, was separated by column chromatography. The structure of the compounds was apparent from spectral data.     

异噁唑基取代的1,2,4-噁二唑啉和吡唑啉类化合物的合成

通过3-乙酰基-5-羟甲基异噁唑衍生的Schiff碱2与由醛肟原位生成的腈氧化物的1,3-偶极环加成反应, “一锅法”制备了5-甲基-5-[5-(叔丁基二甲基硅氧基甲基)-3-异噁唑基]-3-芳基-4-(4-甲氧基苯基)-4,5二氢-1,2,4-噁二唑类化合物4a～4e; 同时由3-乙酰基-5-羟甲基异噁唑衍生的α,β-不饱和酮(5)与取代苯肼的环化反应制备了5-(叔丁基二甲基硅氧基甲基)-3-[(1,5-二芳基)-3-(4,5-二氢吡唑基)]-异噁唑类化合物6a～6i. 所有新化合物的结构经核磁共振谱氢谱和碳谱、质谱、红外光谱以及高分辨质谱等进行了确证.     

1-acyl-2-cyclopentenes and 5-acylbicyclo[2.1.0]pentanes: photochemical and thermal isomerizations

The photochemistry of 1-acyl-2-cyclopentenes varies with the nature of the acyl group. On direct irradiation the aldehyde eliminates carbon monoxide in the singlet excited state, and the aroyl compounds cleave to allyl-aroyl radical pairs both from the singlet and triplet states. In competition to α-cleavage the methyl ketones isomerize in an allylic 1,3-acetyl shift. The lowest-lying reactive triplet of these methyl ketones, characterized as a ³(π, π*) state in the case of the 3-phenyl homologue, undergo oxadi-π-methane rearrangement to a mixture of endo- and exo-5-acetylbicyclo[2.1.0]pentanes.The ground state-acetylbicyclopentanes react in two ways at elevated temperatures: endo-exo stereomutation by selective cleavage of the central cyclopropane bond and reclosure of the 1,3-cyclopentane diradical intermediate, and a rearrangement of the endo isomer to 1-acetyl-2-cyclopentenes on a separate potential energy surface involving a formal 1,2-acetyl shift. The unusually large negative entropy of activation for this latter reaction is suggestive of a concerted electrocyclic process in which the electrons of the internal cyclopropane and the C(5)-acetyl bonds participate.     

Substituted ethyl 2-acyl-3-amino-6-methylthieno[2,3-b]pyridine-4-carboxylates as synthons for novel heterocycles

The triethylamine-catalyzed reaction of 4-substituted ethyl 2-acyl-3-amino-6-methylthieno[2,3-b]pyridine-4-carboxylates IIIa-h with 2,2,6-trimethyl-4H-1,3-dioxin-4-one IV gave 4-substituted ethyl 3-acetyl-2-hydroxy-7-methylthieno[2,3-b:4,5-b′]dipyridine-9-carboxylates Va-h. Some of the thienodipyridines ( V ) reacted with excess IV to give 5-substituted ethyl 3-acetyl-4,8-dimethyl-2-oxo-2H-pyrano[2,3-b]-pyrido[3′,2′:4,5]thieno[2,3-e]pyridine-10-carboxylates VI .