[4+2] Cycloaddition of 1-phosphono-1,3-butadiene with azo- and nitroso-heterodienophiles

Under microwave activation, diethyl 1-phosphono-1,3-butadiene (1) reacted with t-butyl azodicarboxylate (2) and o-nitrosotoluene (5) to furnish quantitatively [4+2] cycloadducts, 3-phosphono-3,6-dihydro-1,2-pyridazine (3) and 6-phosphono-3,6-dihydro-1,2-oxazine (6), respectively. Selective oxidation and/or reduction of 6 led to functionalized δ-aminophosphonic derivatives in cyclic (7, 8) and aliphatic series (9, 10). Intermediate 10 may be cyclized into 2-phosphono-2,5-dihydro-1-pyrrole (12).     

New possibilities of 1,2,4-triazines functionalization: first examples of synthesis and structure of boron-containing 1,2,4-triazines

By oxidation of 3-thioderivatives of 1,2,4-triazine 1a,b 3-alkylsulfonic derivatives 2a,b were obtained. Interaction of the sulfonic derivative 2a with indole leads to 3-oxo-5-indolyl-5-phenyl-as-triazine 4. The sulfone 2a reacts with 1-ethyl-2,6-dimethylquinolinium iodide to give 3-(1-ethyl-6-methyl-1,2-dihydroquinoline-2-methylene)-5-phenyl-1,2,4-triazine 5. The 3-morpholino- 3 and 3-thioderivatives 6, 7a,b of as-triazine were obtained by interaction of the sulfone 2 with morpholine and organic boron-containing thiols. The crystal structure of boron-containing derivative of as-triazine 7b was investigated by X-ray analysis.     

New 2-functionalized 2H-3,4-dihydro-1,4-benzothiazin-3-ones and their application in the synthesis of spiro heterocycles

The reaction of 2-chloro-3,4-dihydro-2H-1,4-benzothiazin-3-ones 1 with enamines is an efficient synthetic method to produce 2-substituted derivatives. The resulting bifunctional compounds such as 6a,b, 7c,d and 8b react with hydrazines to furnish the spiro derivatives of N-aminopyrrole or 3-pyridazinone depending on the direction of the primary nucleophilic attack and the nature of the nucleophile. Under the reaction conditions, spiro pyridazinones 13 are converted into the 3-pyridazinone-4-carboxylic acid derivatives 9 via the 1,4-thiazine ring opening.     

The stereoselective synthesis of γ-lactam derivatives through N(1)-C(4) one carbon ring expansion of β-lactam derivatives

The base induced ring opening of β-lactam derivatives, 3, 5, 7, 9, 11 with LDA gave γ-lactam derivatives, 4, 6, 8, 10, 12 stereoselectively. The γ-lactam derivatives were formed stereoselectively depending on C-3 substituent of β-lactam derivatives.     

Facile synthesis of 5-amino- and 7-amino-6-azaoxindole derivatives

An efficient approach for the formation of 5-amino- and 7-amino-6-azaoxindole derivatives was developed. 2-Amino-4-chloro-3-nitropyridine (8), and its 5-nitro-substituted regioisomer (9), respectively, were obtained by reaction with ethyl malonate. The resulting 2-amino-3/5-nitropyridine derivatives substituted in the 4-position with malonic acid diethyl ester (10, 11) were subjected to reductive cyclization yielding 3-ethoxycarbonyl-6-azaoxindole derivatives 4a and 5a. Protection of the amino function was not required. Intermediates 10 and 11 could also be converted to the corresponding 4-acetic acid ethyl esters 12 and 13 by dealkoxycarbonylation with LiCl, and subsequently cyclized under reductive conditions yielding 3-unsubstituted 5-/7-aminooxazindoles.     

Synthesis of nicotinonitrile derivatives as a new class of NLO materials

4,6-Diaryl-2-(pyrrolidin-1-yl)-nicotinonitriles 2a-k and 3-amino-2,4-dicyano-5-aryl-biphenyls 3a-c were synthesized from 1,3-diaryl-prop-2-en-1-ones 1a-k and malononitrile by a convenient one-pot method. Likewise, the reaction of aromatic aldehydes with malononitrile afforded 6-amino-4-aryl-2-(pyrrolidin-1-yl)-pyridine-3,5-dicarbonitriles 6a-f. The reaction of mesityl oxide with malononitrile gave 5-amino-7-(pyrrolidin-1-yl)-2,4,4-trimethyl-1,4-dihydro-1,6-naphthyridine-8-carbonitrile 8. The NLO studies of the pyridinedinitrile derivatives 6a, b, f showed a high value while that of nicotinonitrile 2b was weak.     

A novel and practical synthetic route for the total synthesis of lycopene

A novel route for the total synthesis of lycopene 1 is described. The synthesis is based on: (i) a condensation between 4,4-dimethoxy-3-methylbutanal 4 and methylenebisphosphonic acid tetraethyl ester 5, leading to the C6-phosphonate 6, followed by (ii) a modified Wittig-Horner reaction between 6 and 6-methyl-5-hepten-2-one 7 producing dimethoxy-3,5,9-triene 8, and (iii) another modified Wittig-Horner reaction between C15-phosphonate 2 and C10-triene dialdehyde 3 producing all-E-lycopene. The synthetic steps are easily operated and practical for the large-scale production.     

The new dispirobino and dispiroansa spermine derivatives of cyclotriphosphazenes

In this study, the crystal structures of the dispiroansa spermine derivatives of cyclotriphosphazene are characterised for the first time. The reaction of spiro-, gem-disubstituted cyclotriphosphazene derivatives, N₃P₃Cl₄R₂ [R = NHPh, (HN(CH₂)₃NH)_0.5, (OCH₂C(CH₃)₂CH₂O)_0.5], (1–3), with spermine (4), in aprotic solvents such as CH₂Cl₂ results in a series of dispirobino spermine derivatives of cyclotriphosphazene (5a, 6a, 7), namely spermine bridged compounds. Whereas, in protic solvents such as CHCl₃ give, dispiroansa derivatives (8–10) namely tetracyclic cyclotriphosphazene. The new series of dispirobino and dispiroansa spermine derivatives of cyclotriphosphazene (5a, 6a, 7–10) have been characterised by elemental analysis, mass spectrometry, X-ray (for 5a, 8, 10) and ¹H, ³¹P NMR spectroscopies.     

Synthesis of novel dansyl-labeled Celecoxib derivatives

Four novel dansyl-labeled derivatives of Celecoxib, a cyclooxygenase-2 (COX-2) selective inhibitor, were designed and synthesized. To realize the fluorophore-linker-approach divergent and convergent synthetic strategies were applied. Therefore Celecoxib p-benzoic acid, 8, was synthesized in a new and convenient way. The yield and the synthetic route to Celecoxib, 1, its pyrazolylic acid, 7, and its pyrazolylic methyl ester, 6, were improved. Through a convenient synthesis 1,11-diamino-3,6,9-trioxundecane, 19, was obtained in high yield and purity and used as a linker for the dansyl moiety.     

Synthesis and properties of 3-arylcyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-diones and related compounds: photo-induced autorecycling oxidation of some amines

Novel 3-phenyl- and 3-(4-nitrophenyl)cyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-diones and the corresponding imino derivatives 5a,b and 6a,b were synthesized in modest to moderate yields by the abnormal and normal aza-Wittig reaction of 2-(1,3-diazaazulen-2-ylimino)triphenylphosphorane with aryl isocyanates and subsequent heterocyclization reaction with a second isocyanate. The related cationic compound, 1-methyl-3-phenylcyclohepta[4,5]imidazo[1,2-a]-1,3,5-triazine-2,4(3H)-dionylium tetrafluoroborate 7a, was also prepared. The electrochemical reduction of these compounds exhibited more positive reduction potentials as compared with those of the related compounds of 3,10-disubstituted cyclohepta[4,5]pyrrolo[2,3-d]pyrimidine-2,4(1H,3H)-dione systems. In a search of the oxidizing ability, compounds 5a, 6a, and 7a were demonstrated to oxidize some amines to give the corresponding imines in more than 100% yield under aerobic and photo-irradiation conditions, while even benzylamine was not oxidized under aerobic and thermal conditions at 100 °C. The oxidation reactions by cation 7a are more efficient than that by 5a and 6a. Quenching of the fluorescence of 5a was observed, and thus, the oxidation reaction by 5a probably proceeds via electron-transfer from amine to the excited singlet state of 5a. In the case of cation 7a, the oxidation reaction is proposed to proceed via formation of an amine-adduct of 7a and subsequent photo-induced radical cleavage reaction.     

Preparation of 3-hydroxyoxindoles with dimethyldioxirane and their use for the synthesis of natural products

This work describes a general protocol for the oxidation of indole and oxindole derivatives with dimethyldioxirane to give 3-hydroxyoxindoles present in many natural products. This strategy allowed us to synthesize the natural product 1, to carry out the first total synthesis of 4, a formal total synthesis of donaxaridine (5) and to achieve the synthesis of pyrroloindoline 8, a debromo analogue of the natural product flustraminol B (7).     

Regioselective addition of Grignard reagents to 2,6-dicyanoanilines and cyclization to new quinazoline derivatives under thermal/microwave irradiation conditions

Two strategies have been developed for the synthesis of novel quinazoline derivatives. 2,6-Dicyanoanilines were reacted with Grignard reagents followed by cyclization to give two quinazoline regioisomers 2 and 3. Alternately 2,6-dicyanoanilines on reaction with Grignard reagents gave imine regioisomers 4 and 5. Each imine regioisomer was separated and independently cyclized to give new quinazoline derivatives 6, 7 and 8, 9, respectively, under different microwave irradiation conditions.     

Synthesis of arylated highly congested indans using a domino sequence

A novel and efficient regioselective synthesis of various arylated highly congested 7-aryl-5-methylsulfanylindan-4-carbonitriles (3a-f), methyl 7-aryl-5-methylsulfanylindan-4-carboxylates (10a-e) and 7-aryl-5-methylsulfanylindan-4-carboxylic acids (11a-e) through base-catalyzed reaction of 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (1a-f) and methyl 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (9a-e) by cyclopentanone (2) has been delineated. The synthetic potential of 2-pyranone was explored further to generate molecular diversity using 6-aryl-4-sec-amino-2-oxo-2H-pyran-3-carbonitriles (7a-h), 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (5a,b) and methyl 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (12a,b) as precursors for the ring transformation by cyclopentanone to assess the effects of substituents on the course of the reaction to obtain highly congested indans, 6,7-diaryl-5-methylsulfanylindan-4-carbonitriles (6a,b), 7-aryl-5-(piperidin-1-yl)indan-4-carbonitriles (8a-h) and methyl 6,7-diaryl-5-methylsulfanylindan-4-carboxylates (13a,b).     

A novel and convenient method for the synthesis of new derivatives of pyrido[3,2-e]pyrrolo[1,2-a][1,4]diazepine-6,11-dione

A novel methodology has been developed for the efficient synthesis of 1,4-pyridopyrrolodiazepine derivatives. The key reaction is the bromination under mild conditions by NBS of compounds resulting via peptide coupling of l-proline methyl ester with 3-aminopyridine-2-carboxylic acid 1, then intramolecular cyclization in the construction of 2-bromo-6a,7,8,9-tetrahydro-5H-pyrido[3,2-e]pyrrolo[1,2-a][1,4]diazepine-6,11-dione 4. This latter is then engaged in cross-coupling reactions to generate 1,4-pyridopyrrolodiazepines derivatives 5a-m, 6a-i, 7, and 8a-c. This strategy provides an efficient method to access a library of compounds based on privileged substructures that are of great interest in drug discovery.     

Syntheses, spectroscopic and structural characterizations and metal ion binding properties of Schiff bases derived from 4′-aminobenzo-15-crown-5

A series of benzyloxybenzaldehyde derivatives (1-4) were synthesized by the reactions of 4-(bromomethyl)benzonitrile with 4-hydroxy-3-methoxybenzaldehyde (vanillin), 2-hydroxy-3-methoxybenzaldehyde (o-vanillin), 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-5-methoxybenzaldehyde. Condensation reactions among the new benzyloxybenzaldehyde derivatives (1-4) with 4′-aminobenzo-15-crown-5 yielded the new Schiff base compounds (5-8). Sodium complexes (5a-8a) and potassium complexes (5b-8b) were prepared with NaClO₄ and KI, respectively. All of these synthesized compounds were characterized on the basis of FT-IR, ¹H and ¹³C NMR, mass spectrometry and elemental analyses data. The solid state structures of compounds 8 and 5a were determined by X-ray crystallography. The extraction abilities of compounds 5-8 were also evaluated in CH₂Cl₂ by using several main group and transition metal picrates, such as Na⁺, K⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cu²⁺ and Zn²⁺.     

Fluxional sulfonyl derivatives of troponoids and colchicinoids

In what represents the first examples of fluxional sulfonyl derivatives, the tosyl group in the couple 4-isopropyltropone/6-isopropyltropone (3/4), the tosyl or mesyl groups in the couple colchicine/isocolchicine (5/6 or 7/8), and the tosyl group in the couples of colchicinoids 9/10 and 11/12, were observed to undergo thermally-induced shift between the two tropolone-like oxygen atoms, likely via a bipyramidal intermediate; recycling of tosylates or mesylates of biologically inactive isocolchicinoids into the corresponding tosylates or mesylates of biologically active colchicinoids affords synthetic value to the unselective tosylation or mesylation of colchiceine.     

Synthesis and characterization of coumarin and dimedone-derived diazabicycles

A series of diazabicyclic derivatives were prepared in three to four steps from p-anisidine and p-nitrobenzaldehyde. The key step of the synthesis involved the acid-catalyzed coupling of 4-aminocoumarin or dimedone derivatives with amino alcohols 3 or 7 to give the ring-opened forms 4, 10, 12 and the ring-closed diazabicycles 5, 6, 9, 11. When 4-alkylaminocoumarins were used as the coupling reagents, the major cyclized product was N-dealkylated diazabicycle 5, rather than the corresponding N-alkylated products. Alternatively, compound 4 was cyclized by DDQ oxidation to produce quinone imine 13. The molecular structures of the synthesized compounds were characterized by X-ray crystallography.     

Synthesis and biological evaluation of new 3-trifluoromethylpyrazolesulfonyl-urea and thiourea derivatives as antidiabetic and antimicrobial agents

Fluorinated pyrazoles, and benzenesulfonylurea and thiourea derivatives as well as their cyclic sulfonylthioureas 2-18 were prepared as hypoglycemic and antibacterial agents. The chemistry involves the condensation of 4-hydrazino benzenesulfonamide hydrochloride with 1-trifluoromethyl diketones 1 to give pyrazole derivatives 2 which upon bromination gave the bromopyrazole 3. Reaction of 2 or 3 with isocyanates and isothiocyanates gave the corresponding ureas 4 and 5 and thioureas 6 and 7. Cyclization of thiourea derivatives with ethyl bromoacetate, ethyl β-bromopropionate, 1,3-dichloroacetone and α-bromoacetophenone yielded the corresponding 4-oxothiazolidines 8 and 9, 4-oxo-5,6-dihydrothiazine 10, 5-oxo-4,5-dihydrothiazines 11 and 12 and thiazolines 13 and 14. Preliminary biological screening of the prepared compounds revealed significant antidiabetic and antibacterial activities.     

Total synthesis of (±)-camphorataimides and (±)-himanimides by NaBH4/Ni(OAc)2 or Zn/AcOH stereoselective reduction

Maleic anhydride 1 of Antrodia camphorate, which can be isolated from Chinese herbal medicine, is achieved in which the longest linear sequence is only five steps, in 40% overall yield from commercially available succinic anhydride. The crucial antrodimides 3 and 2 can be readily transformed by the chemoselective reduction with Zn/AcOH and NaBH₄/Ni(OAc)₂·4H₂O to afford the naturally occurring camphorataimides, 4 and 5, in high yields as well, respectively. This synthetic strategy can also be modified to give access to a variety of different maleic acid derivatives, himanimides 6-8.     

Synthesis of some tetrazole fused pyrido[2,3-c]coumarin derivatives from a one-pot three-component reaction via intramolecular 1,3-dipolar cycloaddition reaction of azide to nitriles

Some novel tetrazole fused pyrido[2,3-c]coumarin derivatives 5/7/9 were synthesized from a one-pot three-component reaction of 4-chloro-3-formylcoumarins 2, sodium azide 3, and alkyl/aryl acetonitriles 4/6/8.