Lewis acid-promoted cascade reaction of primary amine, 2-butynedioate,and propargylic alcohol: a convenient approach to 1,2-dihydropyridines and 1H-pyrrolo[3,4-b]pyridine-5,7(2H,6H)-diones

1,2-Dihydropyridine-5,6-dicarboxylates were efficiently constructed through a cascade reaction of primary amine, 2-butynedioate and propargylic alcohol in the presence of Lewis acid under mild conditions. As exceptional, 1H-pyrrolo[3,4-b]pyridine-5,7(2H,6H)-diones were approached when the primary amine was methylamine. Possible mechanism for the formation of 1,2-dihydropyridine skeleton is proposed. The process involves 1,3,4-pentatrien-1-amine as a key intermediate that formed in situ by trapping allenic carbocations with enamines.     

Easy access to medium rings by entropy/strain reduction,Part 3. Competition between dihydroazepine and enamine formation in reaction of tetrahalosubstituted dibromides with primary amines

The reaction of Z,Z‐2,3,4,5‐tetrahalo‐2,4‐dien‐1,6‐dibromides ( 3 , R¹ ‐ R⁴ = Cl, Br) with primary amines in the presence of potassium carbonate leads to both the dihydroazepines 4 and secondary enamines 5 . The formation of enamine is suppressed with toluene sulfonamide as nitrogen source. (2Z,4Z)‐2,3,4,5‐Tetrabromo‐hexa‐2,4‐diene‐1,6‐diol (2, R¹ ‐ R⁴ = Br) is atropisomeric in solution.     

3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxoquinoxaline-2-carbonyl chloride as a sensitive fluorescence derivatization reagent for amines in liquid chromatography

A rapid and sensitive method for the fluorescence derivatization of primary and secondary amines is described, based on the reaction of the amines with 3,4-dihydro-6,7-dimethoxy-4-methyl- 3-oxoquinoxaline-2-carbonyl chloride. Cyclohexylamine, n-hexylamine and di-n-butylamine were used as model compounds to optimize the derivatization conditions. The reagent reacts with the amines in acetonitrile in the presence of potassium carbonate very rapidly to give the corresponding fluorescent amides, which can be separated on a reversed-phase column, TSKgel ODS-80TM, with aqueous acetonitrile as eluent. Alcohols and amino acids did not give any fluorescent products under the derivatization conditions. The detection limits are in the range 5–50 fmol per 20-μl injection. Reactions with other amines are also discussed.     

抗肿瘤氟喹诺酮C3等排衍生物——噁二唑曼尼希碱衍生物的合成和抗肿瘤活性

用噁二唑硫酮杂环作为培氟沙星(1)的C3羧基电子等排体,得中间体C3噁二唑硫酮4(5),再将其与仲胺或取代苯胺及甲醛通过氨甲基化反应形成系列氟喹诺酮C3噁二唑硫酮曼尼希碱(6a~6j)目标化合物。 用元素分析、1H NMR和MS测试技术确证了目标化合物的组成和结构。 采用MTT法评价了目标化合物对体外培养人肝癌Hep-3B细胞生长的抑制活性。 结果表明,10种目标化合物活性均显著高于对照化合物1的活性,并且脂肪胺曼尼希碱的活性高于芳香胺曼尼希碱的活性。     

Synthesis,steric structure,and biological activity of 5-methyl-2-(morpholin-4-ylamino)-5,6-dihydro-4H-1,3-thiazin-4-one

Russian Journal of General Chemistry - New 5,6-dihydro-1,3-thiazin-4-one derivatives have been synthesized by one-pot reaction of morpholin-4-amine and adamantan-1-amine with methacryloyl...     

Reactions of trifluoro- and hexafluoroacetylacetones with thiobenzoylhydrazine

The reaction of thiobenzoylhydrazine with trifluoroacetylacetone leads to the product of condensation at the CH₃C=O bond with the 5-hydroxy-2-pyrazoline structure. The tautomeric transition to the 2,3-dihydro-1,3,4-thiadiazole isomer occurs in solution. This isomer undergoes the cleavage to 2-methyl-5-phenyl-1,3,4-thiadiazole and trifluoroacetone. The reaction of thiobenzoylhydrazine with hexafluoroacetylacetone affords one of diastereomers of [3,5-dihydroxy-3,5-bis(trifluoromethyl)pyrazolidin-1-yl](phenyl)thioketone, which at equilibrium is transformed in solution into the second diastereomer of the 3,5-dihydroxypyrazolidine form followed by the elimination of water elements and formation of a tautomeric 5-hydroxy-2-pyrazoline-2,3-dihydro-1,3,4-thiadiazole mixture.     

Synthesis,Reactions, and Anticancer Activity of Some 1,3,4-Thiadiazole/Thiadiazine Derivatives of Carbazole

A novel method for the synthesis of 1,3,4-thiadiazole and 1,3,4-thiadiazine derivatives bearing a carbazole moiety is described. Carbazole was transformed into carbazole-9-thiocarbohydrazide in two steps. This compound was allowed to react with various electrophiles to yield 1,3,4-thiadiazole derivatives. The reaction with bifunctional electrophiles led to 1,3,4-thiadiazines. 2-(Carbazol-9-yl)-5,6-dihydro-4H-1,3,4-thiadiazin-5-one reacted with piperidine and formaldehyde to yield the 4-(piperidin-1-ylmethyl) derivative. The reaction with aromatic aldehydes led to the corresponding 6-arylidene derivatives, which were transformed into pyrimidino[4,5-e]-1,3,4-thiadiazines and pyrazolo[3,4-e]-1,3,4-thiadiazines by a reaction with guanidine, acetamidine, or phenylhydrazine, respectively. Structures of the products were confirmed by ¹H NMR, ¹³C NMR, IR, and mass spectrometric measurements. Selected examples of products were screened for anticancer activity.     

Asymmetric 1,3-dipolar cycloaddition of N-metalated azomethine ylides to methyl (S)-2-(p-tolylsulfinyl)acrylate. Synthesis of optically pure 2,4,5-trisubstituted 2,5-dihydro-1H-pyrroles

The first 1,3-dipolar reaction of azomethine ylides with optically pure vinyl sulfoxide are reported. The presence of the sulfinyl group increase the reactivity of the acrylate moiety as a dipolarophile, and the reactions evolve with complete regio- and endo-selectivities. Nevertheless, mixtures of the two diastereoisomers 4 and 5 (75-88% de) resulting from the anti dipole/s-cis dipolarophile and syn dipole/s-trans dipolarophile approaches, respectively, are obtained. The stereoselectivity can be controlled by using THF or MeCN as solvents or by changing the reaction temperature in MeCN. After separation of the cycloadducts, optically pure 2,5-dihydro-1H-pyrroles are easily obtained by pyrolytic desulfinylation.     

Rhodium-catalyzed reaction of terminal alkynes with allylamine leading to (E)-3-alkylidene N-heterocycles

Terminal alkynes react with allylamine in the presence of a RhCl(PPh3)3 catalyst to give (E)-3-alkylidene-3,4-dihydro-2H-pyrroles. The products consist of two molecules of alkyne and one molecule of allylamine. Although dimers, trimers, and oligomers of alkynes are also obtained as byproducts, the addition of various ammonium salts to the reaction suppresses such oligomerization, resulting in an increase in product.     

Recyclization of 5-Amino- oxazoles as a Route to new Functionalized Heterocycles (Developments of V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine)

The recyclizations of 5-amino- and 5-hydrazine-1,3-oxazoles mainly with electron-withdrawing group in 4^th position are considered. The chemical behavior of these heterocycles is due to the presence of two hidden amide fragments; therefore, the recyclization processes include a stage of nucleophile attack on 2^nd or 5^th position of the oxazole cycle. When the nitrile group is present in 4^th position, it is often involved in the recyclization forming α-aminoazoles. 5-Amino/hydrazine-1,3-oxazoles undergo recyclization both in nucleophilic (amines, hydrazine, thionating agents) and electrophilic medium ((trifluoro)acetic acid, other acylating agents). The numerous types of functionalized heterocycles can be easily obtained with the usage of these recyclizations, such as the derivatives of 3-amino-6,7-dihydro-5H-pyrrolo[1,2–a]imidazole, imidazolidine-2,4-dione, 1H-pyrazole-3,4,5-triamine, 5,6-diamino-2,3-diphenylpyrimidin-4(3H)-one, 2-(2-R-7-oxo-5-(trifluoromethyl)oxazolo[5,4–d]pyrimidin-6(7H)-yl)acetic acid, 2-R-4-(5-R′-1,3,4-oxadiazol-2-yl)oxazol-5-amine, (amino(5-amino-1,3,4-thiadiazol-2-yl)methyl)phosphonate.     

Synthesis of some N-alkylated 1,2,4-triazoles, 1,3,4-oxadiazoles,and 1,3,4-thiadiazoles based on N-(furan-2-yl-methylidene)-4,6-dimethyl-1H-pyrazolo-[3,4-<Emphasis Type="Italic">b</Emphasis>]pyridine-3-amine

N-(Furan-2-ylmethylidene)-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine-3-amine was prepared and alkyla- ted with the corresponding halo compounds to afford N-alkylated products. 2-[3-(Furan-2-ylmethy- lideneamino)-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-1-yl]acetohydrazide was converted into the key intermediate thiosemicarbazide, which undergoes cyclization reactions under acidic and basic conditi- ons to give 1,2,4-triazole, 1,3,4-oxadiazole, and 1,3,4-thiadiazole derivatives. Condensation of the hyd- razide with monosaccharide aldoses gave the corresponding sugar hydrazones, which on treatment with acetic anhydride readily undergo cyclization reaction to afford oxadiazoline derivatives.     

一锅法合成4-(5-芳基-1,3,4-噻二唑-2-氨甲基)苯酚衍生物

以2-氨基-5-芳基噻二唑衍生物和对羟基苯甲醛为原料,经亲核加成/脱水、还原两步一锅法合成了一系列新的4-(5-芳基-1,3,4-噻二唑-2-氨甲基)苯酚衍生物,反应具有时间短、后处理简单等优点.采用元素分析,NMR,IR以及质谱等多种谱学技术对产物进行了详细表征.     

The ruthenium-catalyzed reduction and reductive N-alkylation of secondary amides with hydrosilanes: practical synthesis of secondary and tertiary amines by judicious choice of hydrosilanes

A triruthenium cluster, (mu3,eta2,eta3,eta5-acenaphthylene)Ru3(CO)7 (1) catalyzes the reaction of secondary amides with hydrosilanes, yielding a mixture of secondary amines, tertiary amines, and silyl enamines. Production of secondary amines with complete selectivity is achieved by the use of higher concentration of the catalyst (3 mol %) and the use of bifunctional hydrosilanes such as 1,1,3,3-tetramethyldisiloxane. Acidic workup of the reaction mixture affords the corresponding ammonium salts, which can be treated with a base, providing a facile method for isolation of secondary amines with high purity. In contrast, tertiary amines are formed with high selectivity by using lower concentration of the catalyst (1 mol %) and polymeric hydrosiloxanes (PMHS) as reducing agent. Reduction with PMHS encapsulates the ruthenium catalyst and organic byproducts to the insoluble silicone resin. The two reaction manifolds are applicable to various secondary amides and are practical in that the procedures provide the desired secondary or tertiary amine as a single product. The product contaminated with only minimal amounts of ruthenium and silicon residues. On the basis of the products and observed side products as well as NMR studies a mechanistic scenario for the reaction is also described.     

Reactions of 6-Amino-5-Cyano-3-Methyl-1,4-Diphenyl-1H 4H-Pyrano[2,3-C]Pyrazole and its Methanimidate

Reaction of 6-amino-5-cyano-3-methyl-1,4-diphenyl- 1H,4H-pyrano[2,3-c]pyrazole 1 with triethyl orthoformate in acetic anhydride gave its methanimidate 2, which reacts with primary aliphatic and aromatic amines to give 4,6-dihydro-3-methyl-1,4-diphenyl-6- (alkyl)pyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidine-5(lH)- imine 3 and the starting compound 1 , respectively. Treatment of 1 with o-aminophenol gave 5-(2-benzoxalyl)- 1,4-dihydro-3-methyl-1,4-diphenylpyrano[2,3-c]pyrazol- 6-amine 9.     

Reactions of some pyranylidene esters with amines

The reactions of 4-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)-2,6-diphenyl-4H-pyran ( 1 ) with primary amines gave the corresponding 1-substituted 1,4-dihydropyridine derivatives. The related benzo derivative of 1 (12) and primary amines gave 3-substituted 3,4-dihydro-2-phenyl-5H-[1]benzopyrano[3,4-c] pyridine-4,5-dione derivatives. With secondary amines, 12 gave 2-phenyl-4H,5H-pyrano[3,4-c] [1]benzopyrane-4,5-dione, and with isopropylamine, N,N-dimethylhydra-zine, and methanolic potassium hydroxide, 12 gave 4-phenacylcoumarin. Some reaction intermediates were isolated which indicate probable reaction paths. The reactions with amines were extended to a naphtho derivative of 1 (19) and to a thia homolog of 12 (24).     

Ringtransformationen von 3-substituiertem 5-Trifluormethyl-1,3,4-thiadiazol-2(3H)-on mit Nucleophilen

Ring Transformations of 3-Substituted 5-Trifluoromethyl-1,3,4-thiadiazol-2(3H)-one with Nucleophiles The 3-chlormethyl-5-trifluoromethyl-1,3,4-thiadiazolone 3 undergoes a ring transformation to 3-acylated 2,3-dihydro-1,3,4-thiadiazoles 4 with many nucleophiles. Upon formal replacement of the chloromethyl group in the 3-position of 3 by an extended bromoalkyl chain (→9a-c) , the reaction with nucleophiles yields 4-acylated 5,6-dihydro-4H-1,3,4-thiadiazines 10 (from 9a ), 4,5,6,7-tetrahydrothiadiazepines 13 (from 9b ) and 5,6,7,8-tetrahydro-4H-1,3,4-thiadiazocines 14 (from 9c ) by ring enlargement. The 3-propargyl-thiadiazolone 17 rearranges with nucleophiles to 4-acylated 6-methylidene-5,6-dihydro-4H-1,3,4-thiadiazines 18 . The structures of the new compounds were elucidated by ¹H- and ¹³C-NMR spectroscopy.     

The reaction of 5-aminoimidazole-4-carbohydrazides with orthoesters

The reaction of 5-aminoimidazole-4-carbohydrazides with orthoesters is shown to yield 1-amino-9-alkyl-hypoxanthines. Similar reaction of anthranilic acid hydrazide is shown to yield 3-amino-4-quinazolone, and not 1,4-dihydro-5H-1,3,4-benzotriazepin-5-one as previously reported.     

Preparation of 2‐amino‐5‐methyl‐7H‐1,3,4‐thiadiazolo[3,2‐α]pyrimidin‐7‐ones

2‐Amino substituted 7H‐1,3,4‐thiadiazolo[3,2‐α]pyrimidin‐7‐ones 11a‐e were prepared by the reaction of 2‐bromo‐5‐amino‐1,3,4‐thiadiazole ( 1b ) and diketene ( 8 ), subsequent cyclocondensation ( 9b → 3b ) and displacement of the bromo substituents by the reaction with primary or secondary amines ( 3b → 11a‐e ). The hydrogen atom 6‐H in the heterobicycle 3b is replaced by a Cl or Br atom in the transformation of 3b → 14a,b. The 2‐bromo‐6‐chloro compound 14a reacts chemoselectively in the 2‐position with dimethylamine ( 14a → 15 ). The structure elucidations are based on one‐ and two‐dimensional NMR techniques including a heteronuclear NOE measurement.     

Transition metal-catalyzed hetero-[5 + 2] cycloadditions of cyclopropyl imines and alkynes: dihydroazepines from simple,readily available starting materials

The first example of a transition metal-catalyzed hetero-[5 + 2] cycloaddition reaction is described. Use of cyclopropyl imines as five-atom components, an alkyne as a two-carbon component, and a Rh(I) catalyst enables a new route to dihydroazepines. This new hetero-[5 + 2] cycloaddition works well with aldimines, ketimines, and with substituted cyclopropanes and affords the desired dihydroazepines in excellent yields as single regioisomers. Use of serial imine formation/aza-[5 + 2] cycloaddition generates the desired dihydroazepines in one operation from three commercially available starting materials. The reaction has been scaled to give gram quantities of dihydroazepine.     

A Novel Approach to the Synthesis of 1,3,4-Thiadiazole-2-amine Derivatives

The main purpose of the study was the development of a new method for synthesis of 1,3,4-thiadiazol-2-amine derivatives in a one-pot manner using the reaction between a thiosemicarbazide and carboxylic acid without toxic additives such as POCl₃ or SOCl₂. The reaction was investigated in the presence of polyphosphate ester (PPE). It was found that, in the presence of PPE, the reaction between the thiosemicarbazide and carboxylic acid proceeds in one-pot through three steps with the formation of corresponding 2-amino-1,3,4-thiadiazole. Using the developed approach five, 2-amino-1,3,4-thiadiazoles were synthesized. The structures of all compounds were proven by mass spectrometry, IR, and NMR spectroscopies.