Synthesis of bastadin analogs through an SNAr coupling strategy

The synthesis of a bastadin-5 analog was achieved in 16% overall yield (16 steps, longest linear sequence) using a strategy of intermolecular S_NAr coupling to create diphenyl ether bonds and sequential amide couplings to close the ring. Noteworthy elements include assembly of all four substituted aryl rings from two simple benzaldehydes, strict regiocontrol of meta- versus para-aryl ether bonds and management of the reductively-sensitive aryl bromine substituents.     

Bromination of 4-(2-thienyl)thiazoles and 2-(2-thienyl)quinoline

Depending on the substituent, the bromination of 4-(2-thienyl)thiazoles and 2-(2-thienyl)quinoline takes place in the 5 position of the thiophene or thiazole ring. When an amino group is present in the 2 position of the thiazole ring, bromination takes place in the 5 position of the thiazole ring. When excess brominating agent is present, a second bromine atom enters the 5 position of the free ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 35–38, January, 1982.     

Conformations of the side chain in N(6)-acetyl- and N(6)-carbamoylsydnoneimines and their salts

The conformations of the exocyclic group of N(₆)-acetyl- and N(₆)-carbamoylsydnoneimines and their salts were studied by means of their vibrational spectra. It is shown that the side chain in compounds that do not contain a bulky substituent in the 4 position of the sydnoneimine ring has primarily a planar syn-s-cis form. When there is a methyl group or a bromine atom in the 4 position, the C=0 group deviates from the plane of the ring and enters into conjugation with the unshared pair of electrons of the N(₆) atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1193–1195, September, 1978.     

Synthesis of Hexadentate Hexahydro-1,3,5-triazine-Based Ligands and their Copper(I) Complexes

Summary.  Hexadentate ligands were formed by the reaction of primary dimethylaminoethyl- or methoxyethylamines with formaldehyde. The resulting N, N′, N″-functionalized hexahydro-1,3,5-triazines contain pending amino or ether functionalities which are able to coordinate to metals in addition to the ring nitrogen atoms. Both ligands were reacted with CuBr, and novel tricopper clusters were isolated and characterized by X-ray structure analysis. In these compounds a ring nitrogen atom, the pending amino or ether functionality, and two bridging bromine atoms coordinate each of the copper atoms. Received January 22, 2002; accepted (revised) March 22, 2002     

Electroreduction of Dibromides of Aromatic Compounds

Electroreduction of 9,10-dibromanthracene and 4,4"-dibromdiphenyl on a glassy-carbon electrode in dimethylformamide shows they undergo dehalogenation, with the bromine atom replaced by hydrogen. In the case of 9,10-dibromanthracene, bromine atoms are abstracted one by one and the final product is anthracene. In the case of 4,4"-dibromdiphenyl two bromine atoms are abstracted simultaneously and the final product is diphenyl; this reaction is accompanied by a polymer formation. With increasing concentration of 4,4"-dibromdiphenyl, the competition between these two reactions shifts in the direction of the polymer formation.     

Phosphorescence enhancement in diphenyl ether in rigid ethanol glass at 77 K

The phosphorescence yield of diphenyl ether increases markedly relative to phenol in ethanol glass at 77 K. Analysis of the results reveals that the phosphorescence enhancement is attributable to increased spin—orbit coupling arising from the non-planarity of the lone-pair orbital of the oxygen atom in diphenyl ether.     

Some novel halogenated phenazine derivatives

3-Amino-10-aryl-2-arylimino-2,10-dihydrophenazines 1 undergo iodination in the 4-position of the phenazine nucleus yielding compounds which are identical with those obtained by oxidation of appropriate N-aryl-o-phenylenediamines with sodium iodate in the presence of acid. Bromination also takes place in this position but a second bromine atom enters the para-position of the arylimino moiety. The isomeric 10-aryl-3-aryl-amino-2,10-dihydro-2-iminophenazines 2 yield unstable iodo-derivatives but undergo bromination in the 1-and 4-position of the phenazine nucléus and in the ortho- and para-positions of the arylamino substituent. Preliminary chlorination experiments indicate that the substitution pattern is analogous to that established for the brominated products. The removal of bromine and iodine from the phenazine ring by reaction with a primary or secondary amine and their replacement by hydrogen rather than by the amine residue is also recorded.     

Reactions of 5-Functionalyzed 2-(1-Haloethyl)furans with Sodium Diethylphosphite and Trialkyl Phosphites

5-(1-Haloethyl)furan-2-carboxylic acid derivatives react with sodium dialkyl phosphite, tri-alkyl phosphite in two directions to form phosphonates and alkenes. The alkene fraction in the reaction pro-ducts diminishes as the electron-acceptor power of the 2-substituent in the ring increases in going from dialkylamide to ether and then to nitrile. 5-Bromoethyl-2-cyanofuran reacts with sodium diethyl phosphite to give no other products than those formed by halogenophilic attack, implying a significant withdrawal of the electron density from the bromine atom in this compound.     

NEW SYNTHETIC METHOD OF 4,4''''-OXYBIS(BENZOIC ACID)AND ITS APPLICATION IN POLYESTER

4,4'-Oxybis(benzoic acid)(Ⅰ)is an important monomer for making synthetic resin,heat resistant filmand liquid crystal fiber,etc.It has been synthesized either by the oxidation of 4,4'-dimethyl diphenylether,or by the electrophilic substitution of diphenyl ether,these substituents introduced into thebenzene ring can be further transformed into carboxylic groups.Diphenyl ethers are usually prepared fromphenols and halobenzenes through Ullmann resction.Due to the high reaction temerature(usually above200℃),long time heating and the formation of isomers,it is difficult to obtain pure products in highyields.     

Synthesis and chemistry of the phenoxasilins and dihydro-dibenzo-oxasilepins

Formation of both sila-functional and carbo-functional phenoxasilins from diphenyl ether and o,o′-dibromodiphenyl ether precursors is described. Tricyclic oxasilepins are formed from o,o′-dibromobenzylphenyl ether by metallation with n-BuLi followed by reaction with dichlorosilanes as well as by ring expansion of an appropriate phenoxasilin. Reactions at the silicon center and at the ring methylene carbon of the oxasilepins are reported, as well as attempts to generate oxasilocins.     

Über zinn-haltige heterocyclen : V. Sn-phenyk-substituierte stannocane, Übergänge von tetraedrischer 4-Zu trigonal-bipyramidaler 5-koordination

A complete series of diphenyl and mixed methyl/chlorine/bromine/iodinephenyl substituted oxadithia- and trithiastannocanes has been prepared by reactions between the respective disodium dithiolates and tin dihalides. The ¹³C NMR chemical shifts of these compounds and the coupling constants J(¹¹⁹Sn¹³C) are dependent upon the magnetic anisotropy of the substituents and the bond angles at the tin atom. The crystal structure of 2,2-diphenyl-1,3,6-trithia-2-stannocane has been determined and refined to R = 0.039. The environment of Sn is a monocapped tetrahedron (transannular distance Sn?S 324.6(1) pm). This type of coordination, intermediate between a tetrahedron and a trigonal bipyramid, is discussed quantitatively and compared with a series of analogous compounds. The eight-membered ring has the boat-chair conformation.     

MECHANISM OF THE REACTION OF DIPHENYL N-BROMOSULFILIMINE WITH SULFIDES,PHOSPHINES AND TERTIARY AMINES

Abstract

The mechanism of the reactions of diphenyl N-bromosulfilimine (I) with such nucleophiles as sulfides, phosphines and tertiary amines was investigated. In the presence of water, (I) reacts with sulfides or phosphines to afford the corresponding sulfoxides or the phosphine oxides in moderate yields; however, the reaction with tertiary amine gave only the N-t-aminosulfilimine derivative. The effect of ring size in the reaction with cyclic sulfides suggests that the reaction proceeds via initial bromine transfer from the nitrogen atom to the sulfur atom of the cyclic sulfides followed by S_N2 type substitution of bromide on the sulfur atom of the cyclic sulfide with the sulfilimino group. The phosphine oxide obtained in the reaction of (I) with optically active methyl n-propyl phenyl phosphine was racemized but retained a small portion of the optical activity. In the case of tertiary amines, even 1,4-diazabicyclo-(2,2,2)-octane (DABCO), in which the back side of the nitrogen atom is blocked, reacted smoothly to afford the corresponding ammonium salts, suggesting the reaction to be of S_N2 type on the nitrogen atom of the sulfilimine.     

Synthesis and matrix metalloproteinase-12 inhibitory activity of ageladine A analogs

Synthesis of the 37 ageladine A analogs was accomplished by employing the total synthetic route of natural ageladine A previously explored by us. From the matrix metalloproteinase-12 (MMP-12) inhibitory activity assay carried out using the novel analogs, it appeared evident that the halogen atom at the 2-position of pyrrole ring was essential for the inhibitory activity and that the introduction of a bromine atom into the 4-position of pyrrole ring is very effective for producing potent activity. In addition, exchange of the pyrrole ring to an imidazole ring was extremely effective in increasing activity, and the analog 29 thus obtained was found to show approximately 4 times more potent activity than natural ageladine A.     

The mass spectral behavior of β-bromoethyl benzoate and some of its ring substituted derivatives: Evidence for oxygen participation in the formation of [M ? Br]+

The expulsion of a bromine atom from the molecular ion of β-bromoethyl benzoate displays a kinetic behavior which resembles that of a rearrangement reaction. The two oxygen atoms in the resulting [M ? Br]⁺ ion become equivalent before or during the secondary decomposition of this ion, as shown by oxygen labeling. In addition, the primary ions generated from benzophenone ethylene ketal and acetophenone ethylene ketal by phenyl and methyl expulsion, respectively, undergo subsequent fragmentation in the same way as the [M ? Br]⁺ from β-bromoethyl benzoate. These results strongly indicate that the carbonyl-oxygen atom participates in the expulsion of bromine. The effect of ring substituents on the competing loss of bromine and McLafferty rearrangement is also discussed.     

Quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group at the sp-hybridized carbon atom in the methylbromoacetylene molecule

This paper reports on our quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group in the reaction of methylbromoacetylene with copper cyanide. According to calculations, the reaction can form a four-membered ring containing a copper atom.     

Palladium‐Catalyzed Reductive Insertion of Alcohols into Aryl Ether Bonds

Palladium on carbon catalyzes C?O bond cleavage of aryl ethers (diphenyl ether and cyclohexyl phenyl ether) by alcohols (R?OH) in H₂. The aromatic C?O bond is cleaved by reductive solvolysis, which is initiated by Pd‐catalyzed partial hydrogenation of one phenyl ring to form an enol ether. The enol ether reacts rapidly with alcohols to form a ketal, which generates 1‐cyclohexenyl?O?R by eliminating phenol or an alkanol. Subsequent hydrogenation leads to cyclohexyl?O?R.     

Practical synthesis of 3-bromo-5,6-dihydropyridin-2-ones via β,γ-unsaturated α-bromo-ketene/imine cycloaddition

An approach to 3-bromo-4-alkyl-6-aryl-5,6-dihydropyridin-2-ones and 3-bromo-5-ethyl-6-aryl-5,6-dihydropyridin-2-ones starting from β,γ-unsaturated α-bromoketenes and imines is reported. The presence of a bromine atom on the double bond allows performing aziridination or bromine displacement with an amine. The reaction gave fused bicyclic N-allyl-aziridines or 3-amino-substituted 5,6-dihydropyridin-2-ones, depending on the substituents on the six-membered ring.     

Effect of halogen atom localization on the level of antimycobacterial activity of 2-amino-4-arylamino-6-methylpyrimidines

Several hydrochlorides of 2-alkyl(cycloalkyl, aralkyl)-5-bromo-6-methyl-4-phenylaminopyrimidines have been synthesized as isosteric analogs of the corresponding 2-alkyl(cycloalkyl, aralkyl)-4-(3-bromophenyl)amino-6-methylpyrimidine hydrochlorides. Moving the bromine atom from the benzene ring into the heterocycle is accompanied by a significant decrease in the level of antimycobacterial activity.     

室温下二氧化氮催化带有给电子取代基的苯和萘的氧化溴化

在室温下,以8.2%的二氧化氮为催化剂,反应管中残留的空气为氧化剂,分子溴为溴化试剂,研究了带有给电子取代基的苯和萘的氧化溴化.使用的低沸点非金属催化剂易于从产物中去除,很少玷污最终产品;但反应后有少量的苯环硝化副产物生成,这会造成催化剂二氧化氮的损耗.反应具有较高的原子经济性,大部分溴原子被转化到产物中.反应产物具有可控性:可通过改变溴源的用量,分别得到单溴化和二溴化产物.初步的机理分析结论为:反应可能经历分子溴和芳环的反应,生成溴代芳烃和溴化氢;然后在氧化氮类物种催化下,生成的溴化氢被氧气氧化为具有反应活性的溴.     

2-(Adamantan-1-yl)imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyridines and Their Derivatives

A series of 1-adamantylimidazo[1,2-a]pyridines has been synthesized. The negative influence of electron-acceptor substituents in the pyridine ring on the alkylation of substituted 2-aminopyridines with bromomethyl (adamantan-1-yl) ketone has been demonstrated. Bromination of adamantylimidazo-[1,2-a]pyridines on boiling in liquid bromine or in the presence of a Lewis acid resulted in insertion of a bromine atom in the imidazole ring without affecting the adamantane nucleus. The compounds studied take part in the Ritter reaction despite the absence of an easily removed groups in the adamantane nucleus.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 761–766, May, 2005.