Efficient synthesis of benzo[g]-and benzo[h]chromene derivatives by one-pot three-component condensation of aromatic aldehydes with active methylene compounds and naphthols

A convenient procedure is reported for the synthesis of benzo[g]-and benzo[h]chromene derivatives via one-pot three-component condensation of aromatic aldehydes with malononitrile or ethyl cyanoacetate and 1-or 2-naphthol in the presence of 10 mol % of titanium tetrachloride as catalyst. The reactions require no solvent; they are characterized by simple experimental procedure and easy isolation and can be performed on enlarged scale. Published in Russian in Zhurnal Organicheskoi Khimii, 2006, Vol. 42, No. 12, pp. 1824–1826. The text was submitted by the authors in English.     

Knoevenagel condensation of aldehydes with active methylene compounds catalyzed by MgC2O4/SiO2 under microwave irradiation and solvent-free conditions

MgC₂O₄/SiO₂ catalyzes the efficient Knoevenagel condensation of aldehydes with active methylene compounds in solvent-free conditions under microwave irradiation to give alkenes derivatives in excellent yields. MgC₂O₄/SiO₂ can be reusable for Knoevenagel condensation. However, ketones have been found to be unsatisfactory in the reaction under the same conditions.     

芳香醛与硫代巴比妥酸固相缩合反应的研究

研究了芳香醛与硫代巴比妥酸固态加热及室温下的缩合反应，两种反应条件得 到同一产物——5—亚烃基硫代巴比妥酸．由^1H NMR，^13C NMR，IR，UV等手段确 定了产物的结构．     

无外加催化剂条件下芳香醛与活性亚甲基化合物的缩合反应和迈克尔加成反应

在DMF溶剂中，不外加催化剂使芳香醛(1)与2,2-二甲基-1,3-二氧六环-4,6-二酮(2)发生缩合反应生成2,2-二甲基-5-芳亚甲基-1,3-二氧六环-4,6-二酮(3a～f)。在同样条件下，芳香醛与5,5-二甲基-1,3-环己二酮(4)则发生缩合和迈克尔加成反应生成2,2'-芳亚甲基双(3-羟基5,5-二甲基-2-环己烯-1-酮)(5a～h)。用单晶X-射线分析法确定了产物5b的晶体结构。     

Three-component condensation of α-nitroacetophenone,aromatic aldehydes,and methylurea

The three-component condensation of aromatic aldehydes, methylurea, and α-nitroacetophenone affords both N(1)-and N(3)-methyl-substituted 4,6-diaryl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones depending on the structure of aldehyde. Intermediate 4,6-diaryl-4-hydroxy-3-methyl-5-nitrohexahydropyrimidin-2-ones and trisubstituted urea, which is the transformation product of the 4-hydroxy-3-methyl derivative in an acidic medium (retro-Henry reaction), were identified in the reaction mixtures. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1141–1145, June, 2007.     

Acylaminoacetyl derivatives of active methylene compounds. 4

Meldrum's acid has been found to be effectively acylated using the imidazolides of N-protected glycines, X-NHCH₂COOH (X = -COPh, -COMe, -Z, -Boc, -COOMe and -COOEt). The corresponding C-acylation compounds were isolated in high yields and were readily converted to the N-protected tetramic acids. It was shown by pmr spectroscopy that these acids exist as the enol tautomers in DMSO-d₆ solution, whereas in deuteriochloroform solution both the enol and keto tautomers can be observed.     

Synthesis of 4-aryl-6-phenyl-2-thioxo-1,2-dihydropyridine-3-carbonitriles by three-component condensation of aromatic aldehydes with cyanothioacetamide and 4,4,4-trifluoro-1-phenylbutane-1,3-dione

4-Aryl-6-phenyl-2-thioxo-1,2-dihydropyridine-3-carbonitriles were synthesized by three-component condensation of aromatic aldehydes with cyanothioacetamide and 4,4,4-trifluoro-1-phenylbutane-1,3-dione. The reaction involved initial formation of Michael adducts which underwent acyl cleavage.     

One-step three-component coupling of aromatic organozinc reagents, secondary amines, and aromatic aldehydes into functionalized diarylmethylamines

Numerous functionalized diarylmethylamines have been synthesized in high yield according to a one-step three-component coupling between an aromatic organozinc reagent, a secondary amine, and an aromatic aldehyde. Both organozinc species and aldehyde can bear a functional group and either aromatic or non-aromatic amines can be used in this versatile procedure.     

Knoevenagel reaction: alum-mediated efficient green condensation of active methylene compounds with arylaldehydes

Abstract

A solvent-free stirred mixture of active methylene compounds, arylaldehyde and 10 mol% alum at 80°C afforded Knoevenagel products in excellent yields. The use of a green catalyst, the solvent-free conditions, and shorter reaction times are the main features of this efficient protocol.     

Unusual carbocyclization in three-component reaction involving acetylacetone,primary amines,and aromatic aldehydes

Russian Journal of General Chemistry -     

FeCl3 as Lewis acid catalyzed one-pot three-component aza-Friedel-Crafts reactions of indoles, aldehydes, and tertiary aromatic amines

A new strategy for the synthesis of 3-diarylmethyl indoles was developed through FeCl₃ as Lewis acid catalyzed three-component aza-Friedel-Crafts reactions of indoles, aldehydes, and tertiary aromatic amines in one-pot. The reactions generated the corresponding 3-diarylmethyl indoles in good yields under mild reaction conditions by using less expensive, readily available, and environmentally benign iron catalyst. It is important to note that the key feature of this reaction is operational simplicity.     

Reactions of 3-formylchromone with active methylene and methyl compounds and some subsequent reactions of the resulting condensation products

This review presents a survey of the condensations of 3-formylchromone with various active methylene and methyl compounds, e.g. malonic or barbituric acid derivatives, five-membered heterocycles, etc. The utilisation of the condensation products for the synthesis of different heterocyclic systems, which is based on the ability of the gamma-pyrone ring to be opened by the nucleophilic attack is also reviewed. Finally, the applications of microwave irradiation as an unconventional method of reaction activation in the synthesis of condensation products is described and the biological activity of some chromone derivatives is noted.     

Et3N-induced demethylation-annulation of 3-alkynyl-4-methoxy-2-pyridones and structurally related compounds in the synthesis of furan-fused heterocycles

Various 3-iodo-4-methoxypyridin-2-ones and related pyrone and coumarin derivatives have been demonstrated as readily available precursors of 2-substituted furan-fused heterocycles by means of in situ sequential Sonogashira-acetylide coupling, dealkylation, and regioselective furan annulation reactions. A Et3N-induced S(N)2 process has been established that accounts for the dealkylation process.     

Asymmetric Pinacol Coupling of Aromatic Aldehydes Catalyzed by TiCl4 （THF） 2－Zn／Chiral Diamines

Asymmetric pinacol coupling of aromatic aldehydes catalyzed by chiral diamines/iow-valent titanium complexes gave corre-sponding pinacois in good yields with high diastereoselectivity and moderate enantioselectivities.     

Highly stereoselective TiCl4-Catalyzed Evans-aldol and Et3Al-mediated Reformatsky reactions. Efficient accesses to optically active syn- or anti-alpha-trifluoromethyl-beta-hydroxy carboxylic acid derivatives

[reaction: see text] The TiCl(4)-catalyzed Evans-aldol reaction of optically active 3,3,3-trifluoropropanoic imide gave the non-Evans syn product stereoselectively, whereas the Reformatsky reaction of 2-bromo-3,3,3-trifluoropropanoic imide in the presence of Et(3)Al led to the Evans anti product. These new approaches enabled us to synthesize all stereoisomers of trifluoromethylated aldol products for the first time.     

Synthesis of 5-azido-4-cyanoimidazole and its reaction with active methylene compounds

Diazotisation of 1-acetamido-5-amino-4-cyanoimidazole 2 using sodium nitrite in aqueous acetic acid gave 5-azido-4-cyanoimidazole 3 in 94% yield. Reaction of 3 with active methylene compounds R¹COCH₂R² [R¹ = Me, R² = COMe; R¹ = Me, R² = COPh; R¹ = Me, R² = COOEt] or malononitrile in the presence of base led either to imidazo[5,1-d][1,2,3,5]tetrazepines 6 and 8 or to imidazolyltriazoles 5 , 7 and 9 , depending on the reaction conditions. Tetrazepine 6c evolves to triazole 7c or 5c respectively in the presence of acid or by further treatment with base. Purine 10 was also isolated in the reaction of 3 with malononitrile.