The effect of the double bond pyramidalization on the mode of the bromination reaction: bromination of benzobicyclononadiene

The bromination of 6,7,8,9-tetrahydro-5H-5,9-ethenobenzo[a][7]annulene yielded regio- and stereospecifically formed dibromides arising from the alkyl shift where the bromine exclusively attacks the double bond from the endo face of the double bond. DFT calculations on model compounds showed that the pyramidalization of the double bond and steric repulsion caused by the methylene protons are responsible for the stereo- and regioselective addition of bromine.     

Unusually high pyramidal geometry of the bicyclic amide nitrogen in a complex 7-azabicyclo[2.2.1]heptane derivative: Theoretical analysis using a bottom-up strategy

The high pyramidalization of the bicyclic amide nitrogen found in the crystal structure of a dipeptide incorporating (1S,2S,4R)-N-benzoyl-2-phenyl-7-azabicyclo[2.2.1]heptane-1-carboxylic acid has been investigated using quantum mechanical calculations. More specifically, a bottom-up strategy based on the study of model molecules of progressive complexity has been used. First, an appropriate quantum mechanical method has been selected by examining the distortion of the amide bond in three simple model molecules. Next, the amide distortion induced by the norbornane ring has been evaluated by considering three different 7-azabicyclo[2.2.1]heptane amides. After this, the suitability of quantum mechanical calculations to predict the effect of the substituents on the pyramidalization of the bicyclic amide nitrogen has been investigated by comparing experimental and theoretical parameters for a number of compounds. Finally, the factors responsible for amide distortion in the (1S,2S,4R)-N-benzoyl-2-phenyl-7-azabicyclo[2.2.1]heptane-1-carboxylic acid derivative have been elucidated using a hierarchical approach. For this purpose, several derivatives were generated by removing or modifying the substituents attached to the 7-azanorbornane system. Results have been discussed in terms of intramolecular specific interactions.     

Synthesis of N-butyloxycarbonylalanyl-1,4dioxa-7-azaspiro[4,4]nonane-8(S)-carboxylic acid ethyl ester

A four-step method has been developed for the synthesis of N-buryloxycarbonylalanyl-1,4-dioxa-7-azaspiro[4,4]nonane-8(S)-carboxylic acid ethyl ester through the formation of N-benzyloxycarbonyl-1,4-dioxa-7-azaspiro[4,4]nonane-8(S)-carboxylic acid ethyl ester.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 663–665, May, 1996. Original article submitted January 31, 1996.     

Design and synthesis of novel tricycles based on 4H-benzo[1,4]thiazin-3-one and 1,1-dioxo-1,4-dihydro-2H-1lambda6-benzo[1,4]thiazin-3-one

This paper reports our recent efforts to develop novel tricycles based on 4H-benzo[1,4]thiazin-3-one ( 2) and 1,1-dioxo-1,4-dihydro-2H-1lambda(6)-benzo[1,4]thiazin-3-one (3) using 1,5-difluoro-2,4-dinitrobenzene (1). All of these tricycles integrate two privileged structures into one skeleton, including 3,8-dihydro-5-thia-1,3,8-triaza-cyclopenta[b]naphthalene-7-one (4, 10, 12), 5,5-dioxo-3,5,6,8-tetrahydro-5lambda(6)-thia-1,3,8-triaza-cyclopenta[b]naphthalene-7-one (5, 11), 3,8-dihydro-5-thia-1,2,3,8-tetraaza-cyclopenta[b]naphthalene-7-one (6), 5,5-dioxo-3,5,6,8-tetrahydro-5lambda(6)-thia-1,2,3,8-tetraaza-cyclopenta[b]naphthalene-7-one (7), 3,8-dihydro-1H-5-thia-1,3,8-triaza-cyclopenta[b]naphthalene-2,7-dione (8), and 5,5-dioxo-3,5,6,8-tetrahydro-1H-5lambda(6)-thia-1,3,8-triaza-cyclopenta[b]naphthalene-2,7-dione (9). A typical library of scaffold 5 was synthesized in a parallel solution-phase manner and analyzed by HPLC-UV-MS or HPLC-UV-ELSD method.     

Mass spectra of 1,2-alkylenedioxy-substituted and related benzofurazans and benzofuroxans: differentiation between linear and angular isomers.

The electron ionization (EI) mass spectra of [1,3]-dioxolo-, 6, 7-dihydro-[1,4]-dioxino-, 7,8-dihydro-6H-[1,4]dioxepino-, 6,7,8, 9-tetrahydro[1,4]dioxocino-, 7,8,9,10-tetrahydro-6H-[1,4]dioxonino- and 6,7,8,9,10,11-hexahydro[1,4]dioxecino[2,3-f]-2,1, 3-benzoxadiazoles (benzofurazans) and the corresponding 1-oxides (benzofuroxans), all linear isomers, are reported. Also reported are the EI mass spectra of the corresponding angular isomers, [1, 3]dioxolo-, 7,8-dihydro[1,4]dioxino-, 8,9-dihydro-7H-[1,4]dioxepino-, 7,8,9,10-tetrahydro[1,4]dioxocino-, 8,9,10,11-tetrahydro-7H-[1, 4]dioxonino-, 7,8,9,10,11,12-hexahydro[1,4]dioxecino[2,3-e]-2,1, 3-benzoxadiazoles and the corresponding 1-oxides. The relative abundance of the fragment ion of m/z 80 is characteristically enhanced in the spectra of the angular derivatives compared to the spectra of the linear counterparts. Collisionally activated decomposition studies show that it is structurally identical whether derived from the benzofurazans or the benzofuroxans. The relative abundance of the m/z 80 ion serves to distinguish between linear and angular isomeric pairs. In addition, the fragment ion at m/z 80 also serves to differentiate between the pairs of isomers, analogous to linear and angular, of six acyclic methoxy- and methoxymethyl-substituted benzofurazans and their corresponding benzofuroxans.     

Synthesis of benzazepines and their rearrangement to quinolines and pyrrolo(2,3-b) quinolines

BECKMANN or SCHMIDT rearrangement of ethyl trans-4-oxo-1-phenyl-2-tetralincarboxylate ( 2 ) affords ethyl trans-2,3,4,5-tetrahydro-2-oxo-5-phenyl-1H-benzo [b] azepine-4-carboxylate ( 4 ). Mild treatment of trans-2,3,4,5-tetrahydro-1-methyl-2-oxo-5-phenyl-1 H-benzo-[b] azepine-4-carboxylic acid ( 7 ) with thionyl chloride and pyridine in dimethylformamide and subsequent reaction with an amine yields the corresponding benzazepine-4-carboxamide. If he it is applied during the preparation of the acid chloride, rearrangement occurs yielding cis and trans derivatives of hydrocarbostyril. 2,3,4,5-Tetrahydro-1,4-methano-1-methyl-5-phenyl-1 H-benzo-[b] azepinium chloride ( 25 ) reacts with primary or secondary amines to cis-tetrahydroquinoline derivatives. When heated above its melting point, trans-4,5-dihydro-2-methylamino-5-phenyl-3H-benzo-[b] azepine-4-carboxylic acid ( 29 ) rearranges with elimination of water to a mixture of cis-and trans-2,3,3a,4-tetrahydro-1-methyl-2-oxo-4-phenyl-1H-pyrrolo [2,3-b] quinoline ( 32 and 31 ). The reduction of 31 was investigated. The mechanisms of the rearrangements are discussed.     

Two directions of the reaction of 3,4-dihydroxy-6-oxoalka-2,4-dienoic acid esters with anthranilic acid hydrazide

Methyl 3,4-dihydroxy-6-oxoalka-2,4-dienoates reacted with anthranilic acid hydrazide to give methyl [5-alkyl-1-(2-aminobenzamido)-2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrol-2-yl]acetates. The reaction of anthranilic acid hydrazide with ethyl 3,4-dihydroxy-6-oxohepta-2,4-dienoate afforded ethyl (2Z)-(3a-hydroxy-2-methyl-10-oxo-3,3a,5,10-tetrahydro-4H-pyrazolo[5,1-c][1,4]benzodiazepin-4-ylidene)acetate as solvate with one methanol molecule. The structure of the isolated compounds was determined on the basis of IR and NMR spectra and X-ray diffraction data.     

1, 5, 6, 7-Tetrahydro-2H-[1,4]diazepin-5,7-dione aus Malonimiden und 3-Dimethylamino-2,2-dimethyl-2H-azirin

1, 5, 6, 7-Tetrahydro-2H-[1, 4]diazepin-5, 7-diones from Malonimides and 3-Dimethylamino-2, 2-dimethyl-2H-azirine Reaction of the aminoazirine 1 with malonimides of type 7 in 2-propanol at room temperature leads to the 1,4-diazepine derivatives of type 9 (Scheme 3). The structure of 6, 6-diethyl-3-dimethylamino-2,2-dimethyl-1,5,6, 7-tetrahydro-2H- [1,4] diazepin-5, 7-dione ( 9a ) has been proved by single crystal X-ray analysis (Chapter 4). Reduction of the 7-membered heterocycle 9a with sodium borohydride yields the perhydro-[1,4]diazepin-5, 7-dione 10 , while 9a in ethanol at 60° undergoes a ring contraction to the 4 H-imidazole derivative 11a (Scheme 4): Mechanisms of these two reactions are discussed in comparison with previously reported reactions (Chapter 5).     

Conversion of acetamido- and nitro-substituted ortho-azidonitro derivatives of 2,3,4,5-tetrahydrobenzo [b][1,4]dioxocin to the corresponding furoxans and furazans in the gas phase

Electron impact ionization of the five isomeric 2,3,4,5-tetrahydro-9-azido-7,8-dinitro-, 2,3,4,5-tetrahydro-8-azido-7,9-dinitro-, 2,3,4,5-tetrahydro-8-azido-7,10-dinitro-, 2,3,4,5-tetrahydro-7-azido-8,9-dinitro-, 2,3,4,5-tetrahydro-7-azido-8,10-dinitro- and the related 2,3,4,5-tetrahydro-7-acetamido-8-azido-9-nitro-, 2,3,4,5-tetrahydro-7-acetamido-9-azido-8-nitro-, 2,3,4,5-tetrahydro-9-acetamido-7-azido-8-nitro-, 2,3,4,5-tetrahydro-10-acetamido-7-azido-8-nitrobenzo[b] [1,4]dioxocin derivatives furnished, after elimination of nitrogen, the corresponding nitro and acetamido dioxocino-annelated benzofuroxans. Further loss of oxygen from the latter afforded the corresponding benzofurazans. It was shown in two cases that these processes occur primarily upon electron impact ionization, without excluding some small fraction undergoing a thermal degradation process. The proposed fragmentation patterns are supported by high-resolution and mass-analyzed ion kinetic energy spectroscopic data. Similar work on the unsubstituted 6,7-dihydro[1,4]dioxino[2,3-f]- and 7,8-dihydro-6H-[1,4]dioxepino[2,3-f]-2,1,3-benzoxa-diazole 1-oxide reveal that loss of oxygen from the molecular ion to furnish the corresponding benzofurazans is the result of electron impact ionization (at least in part).     

Molecular Mechanisms of Photosensitization Induced by Drugs XII. Photochemistry and Photosensitization of Rufloxacin: An Unusual Photodegradation Path for the Antibacterials Containing a Fluoroquinolone-like Chromophore

The UVA irradiation of 9-fluoro-2,3-dihydro-10-4'-methyl-1' -piperazinyl-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzo-thiazine-6-carboxylic acid, rufloxacin, a fluoroquinolone antibacterial that shows photosensitizing properties toward biological substrates, leads to formation of two main steady photoproducts characterized by a decarboxylation process and an opening of the piperazinyl ring, respectively. The deprotonation of the 10-piperazinyl group and the dissociation of the 6-carboxyl group of rufloxacin are strictly pH dependent. The photosensitizing activity was tested toward membranes as biological targets. Red blood cell hemolysis and lipid peroxidation were considered as markers of photosensitization. Ultraviolet A-induced damage is strongly influenced by the presence of oxygen, it is triggered by transient species, such as singlet oxygen and free radicals, photogenerated via rufloxacin irradiation, whereas no drug photoproduct is involved in the photosensitization process.     

Benzofused tricycles based on 2-quinoxalinol

This paper describes our recent efforts to synthesize novel compound scaffolds integrating 2-quinoxalinol with privileged structures of 1,3-dihydro-benzoimidazol-2-one, 1,3-dihydro-benzoimidazole-2-thione, 3-hydroxy-1H-quinoxalin-2-one, 2H-benzo[1,4]oxazin-3-ol, 2H-benzo[1,4]thiazin-3-ol, and 1,3,4,5-tetrahydro-benzo[1,4]diazepin-2-one, respectively. Eight novel benzofused tricycles and their substituent diversity points were developed. These include pyrazino[2,3-g]quinoxaline-2,8-diol (I), 3-hydroxy-6,8,9,10-tetrahydro-1,4,6,10-tetraaza-cyclohepta[b]naphthalen-7-one (II), 6-hydroxy-4H-1-oxa-4,5,8-triaza-anthracen-3-one (III), 6-hydroxy-4H-1-thia-4,5,8-triaza-anthracen-3-one (IV), 6-hydroxy-1,1-dioxo-1,4-dihydro-2H-1lambda(6)-thia-4,5,8-triaza-anthracen-3-one (V), 6-hydroxy-1,3-dihydro-imidazo[4,5-g]quinoxalin-2-one (VI), 6-hydroxy-1,3-dihydro-imidazo[4,5-g]quinoxaline-2-thione (VII), and 7-hydroxy-1,4-dihydro-pyrazino[2,3-g]quinoxaline-2,3-dione (VIII). This strategy of integrating two benzofused privileged structures into one molecule may provide a greater chance for the discovery of novel lead compounds.     

Synthesis of dihydro-1,3-thiazine derivatives. II

1-Oxo-3-thioxo-5-hydroxy-2-acyl-2,3-dihydro-1H-1,3-thiazino[6,5-c]quinolines were obtained for the first time by condensation of 2-hydroxy-3-mercaptoquinoline-4-carboxylic acid with acyl isothiocyanates. Alkyl and acyl isothiocyanates react with 1-methyl-2-oxo-3-mercapto-1, 2-dihydroquinoline-4-carboxylic acid to give 1,5-dioxo-3-thioxo-2-alkyl (acyl)6-methyl-2, 3,5,6-tetrahydro-1H-1,3-thiazino [6,5-c] quinolines.See [1] for communication I.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 641–643, May, 1973.     

Synthesis and Properties of 1,3-Diaryl-5,6-dihydro-8H-imidazo[2,1-c]-1,4-oxazinium Bromides

It has been established that the condensation of 3-(4-methoxyphenylamino)-5,6-dihydro-2H-1,4-oxazine with substituted phenacyl bromides occurs at the exocyclic nitrogen atom with formation of 3-aryl-3-hydroxy-1-(4-methoxyphenyl)-2,5,6,8-tetrahydro-3H-imidazo[2,1-c]-1,4-oxazinium bromides. By treatment of the latter with acetic anhydride 3-aryl-1-(4-methoxyphenyl)-5,6-dihydro-8H-imidazo[2,1-c]-1,4-oxazinium bromides are formed. The structures of the compounds synthesized were determined via ¹H NMR spectroscopy and X-ray diffraction.     

The Mannich reaction in the synthesis of N,S-containing heterocycles 3. Unexpected direction of the aminomethylation reaction of N-methylmorpholinium 1-amino-2,4-dicyano-4-ethoxycarbonyl-1,3-butadienethiolate. One stage cascade synthesis of new derivatives of pyrido[1,2-<Emphasis Type="Italic">a</Emphasis>][1,3,5]triazine

The interaction of N-methylmorpholinium 1-amino-2,4-dicyano-4-ethoxycarbonyl-1,3-butadienethiolate with primary amines and formaldehyde leads to the formation of ethyl esters of 7-cyano-6-thioxo-1,3,4,6-2H-pyrido[1,2-a][1,3,5]triazine-9-carboxylic acid in place of the expected derivatives of pyrido[2,1-b][1,3,5]thiadiazine. The structure of the ethyl ester of 7-cyano-3-phenyl-6-thioxo-1,3,4,6-2H-pyrido[1,2-a][1,3,5]triazine-9-carboxylic acid was demonstrated by X-ray structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1075–1081, July, 2007.     

Synthesis of bicyclic tertiary alpha-amino acids

Novel bicyclic alpha-amino acids, exo and endo-1-azabicyclo[2.2.1]heptane-2-carboxylic acid, 1-azabicyclo[2.2.1]heptane-7-carboxylic acid, and 1-azabicyclo[3.2.2]nonane-2-carboxylic acid have been readily synthesized for the generation of neuronal nicotinic receptor ligands. Alkylation of glycine-derived Schiff bases or nitroacetates with cyclic ether electrophiles, followed by acid-induced ring opening and cyclization in NH4OH, allowed for the preparation of substantial quantities of the three tertiary bicyclic alpha-amino acids.     

Synthesis of a novel tricyclic 4-quinolone. Incorporation of a spiro-cyclopropyl group at N1 by bridging to C2

An important pharmacophore in many quinolone antiinfectives is the N1 cyclopropane. By incorporating the cyclopropane into a N1 to C2 bridge, the first quinolone substrate incorporating a spiro fused cyclopropane, 8,9,10-trifluoro-2,3,4,6-tetrahydro-6-oxospiro[1H-benzo[c]quinolizine-1,l-cyclopropane]-5-carboxylic acid, ethyl ester ( 8 ), was prepared.     

The synthesis of a series of 7-amino-1-cyclopropyl-8-fluoro-1,4-dihydro-4-oxo-1,6-naphthyridine-3-carboxylic acids as potential antibacterial agents

A series of 7-amino-1-cyclopropyl-1,4-dihydro-8-fluoro-4-oxo-1,6-naphthyridine-3-carboxylic acids has been prepared and evaluated for antibacterial activity. These compounds were prepared by the displacement of the chloro substituent from 7-chloro-1-cyclopropyl-1,4-dihydro-8-fluoro-4-oxo-1,6-naphthyridine-3-carboxylic acid employing the requisite nitrogen nucleophile to produce the title compounds. The naphthyridine acid was synthesized in ten steps from ethyl 2,4-dihydroxy-3-nitro-5-pyridinecarboxylate. The key step in the sequence was a Schiemann reaction carried out using the hexafluorophosphate salt of the diazonium ion derived from ethyl 3-amino-2,4-dichloro-5-pyridinecarboxylate.     

Ionic Liquid-Mediated Facile Synthesis and Antimicrobial Study of Thiazolo [2,3-b]Benzo[h]Quinazolines and Thiazino[2,3-b] Benzo-[h]Quinazolines

Abstract

8-Methoxy-4-phenyl-3,4,5,6-tetrahydrobenzo[h]quinazoline-2(1H)-thione, obtained by the condensation of 2-benzylidene-6-methoxy-3,4-dihydronapthalene-1(2H)-one with thiourea, on reaction with chloroacetic acid and 3-chloropropanoic acid in the presence of the ionic liquid N-methylpyridinium tosylate furnishes 3-methoxy-7-phenyl-7,10-dihydro-5H- benzo[h]thiazolo[2,3-b]quinazoline-9(6H)-one and 3-methoxy-7-phenyl-5,6,10,11-tetrahydro- benzo[h][1,3]thiazino[2,3-b]quinazoline-9(7H)-one. Further, condensation of the thione with 1,2-dibromoethane and 1,3-dibromopropane yields 3-methoxy-7-phenyl-6,7,9,10-tetrahydro-5 H-benzo[h]thiazolo[2,3-b]quinazoline and 3-methoxy-7-phenyl-5,6,7,9,10,11-hexahydrobenzo [h][1,3]thiazino[2,3-b]quinazoline respectively. Arylidene derivatives have been obtained by two routes. The structures of the cyclized compounds have been established on the basis of elemental analysis and spectroscopic data. The synthesized compounds were screened for antimicrobial activity. Some of the compounds showed promising antimicrobial activities.     

Synthesis of New Fluorinated Derivatives of Quinolinecarboxylic Acids

Ethyl esters of 1-(7-Z-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carbamoyl)-5-X-6,7,8-trifluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acids (X = H, F; Z = pyrrolidino-, piperidino-, hexamethylenimino-, morpholino-, thiomorpholino-) have been synthesized by the interaction of quinolone-3-carboxylic acid hydrazides with ethyl esters of 3-ethoxy-2-(polyfluorobenzoyl)acrylic acid . It was shown possible to cyclize intramolecularly the esters obtained with the formation of 1,3,4-oxadiazino[6,5,4-i,j]quinoline derivatives.     

Preparation and reactions of some 1,2,3,4-Tetrahydro-2,3-disubstituted 7(or 8)hydroxy-1,4-dioxopyrazino[1,2-a] indoles

1,2,3,4-Tetrahydro-2,3-disubstituted 7(or 8) hydroxy-1,4-dioxopyrazino[1,2-a]indoles have been prepared by the condensation of 6(or 5)benzyloxyindole-2-carbonyl chloride with d1-N- alkylamino acid ethyl esters in the presence of triethyl amine followed by the hydrogenolysis over palladium-carbon. Methylation and alkaline hydrolysis of 1,2,3,4-tetrahydro-2-benzy1-1,4-dioxopyrazino[1,2-a]indole are discussed.