Wide Range Of Nucleophiles Research Articles

Synthetic applications of cationic iron and cobalt carbonyl complexes

Metal carbonyl stabilized cationic species react with a wide range of nucleophiles under mild conditions, and have thus found many synthetic applications. In this Perspective, we describe the utility of iron carbonyl dienyl cations in solution and solid phase parallel synthesis, and in the development of a new synthetic route towards oseltamivir phosphate (Tamiflu). We also discuss the solid phase version of the Nicholas reaction, employing cobalt carbonyl stabilized propargylic cations, and giving access to substituted alkynes.

Gold-catalyzed hydrofunctionalization of allenes with nitrogen and oxygen nucleophiles and its mechanistic insight

A wide range of nucleophiles, such as amines and alcohols, reacted intermolecularly with various allenes in the presence of gold catalysts to give the corresponding hydrofunctionalization products in high yields. The intermolecular hydroamination of chiral allenes with aromatic and aliphatic amines proceeded with high to good enantioface selectivities to afford the corresponding chiral allylic amines. On the other hand, in the case of the intermolecular hydroalkoxylation of chiral allenes, no chirality transfer was observed. This marked contrast on the chirality transfer indicates that the mechanisms of gold-catalysis between hydroamination and hydroalkoxylation are different.

Transition metal carbene chemistry 7: Nucleophilic substitution reactions of imidazolide and benzimidazolide ions with Fischer carbene complexes in MeOH

Rate constants for the nucleophilic substitution reactions of imidazolide (IZ −) and benzimidazolide (BIZ −) ions with 4- Cr- Z and 5 in MeOH at 25 °C are reported and Hammett ρ values are evaluated to be 1.50 ± 0.10 and 1.51 ± 0.08 for 4- Cr- Z-IZ − and 4- Cr- Z-BIZ − reactions, respectively. The comparable reactivity and also almost identical ρ values for these reactions indicate that there is no difference in sensitivity towards electronic effects due to slightly bigger size of BIZ − over IZ − and bond formation at the transition states are equally progressed. The higher ρ values for these reactions compared to those with a wide range of nucleophiles may arise mainly due to lower polarity of the solvent MeOH which enhances the requirement for stabilization of the negative charge in the transition state by the Z-substituents.

O6-(Benzotriazol-1-yl)inosine Derivatives: Easily Synthesized, Reactive Nucleosides

A novel class of O6-(benzotriazol-1-yl)inosine as well as the corresponding 2'-deoxy derivatives can be conveniently prepared by a reaction between sugar-protected or -unprotected inosine or 2'-deoxyinosine nucleosides and 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP). The reaction appears to proceed via a nucleoside phosphonium salt, and in the absence of any additional nucleophile, the released 1-hydroxybenzotriazole undergoes reaction with the formed phosphonium salt leading to the requisite O6-(benzotriazol-1-yl)inosine or 2'-deoxyinosine derivatives. Isolation and characterization of the phosphonium salt as well as analysis by 31P{1H} NMR appear to be consistent with this reaction pathway. The resulting O6-(benzotriazol-1-yl)inosine derivatives are effective as electrophilic nucleosides, undergoing facile reactions with a variety of nucleophiles such as alcohols, phenols, amines, and a thiol. Unusual and challenging nucleoside derivatives such as an aryl-bridged dimer, a nucleoside-amino acid conjugate, and a nucleoside-nucleoside dimer have also been synthesized from the O6-(benzotriazol-1-yl)-2'-deoxyinosine derivative. Finally, a fully protected DNA building block, the O6-(benzotriazol-1-yl)-2'-deoxyinosine 5'-O-DMT 3'-O-phosphoramidite, has been prepared and a preliminary evaluation of its use for DNA modification has been performed. Results from these studies indicate several important facts: A single, simple methodological approach provides a class of stable, isolable ribo and 2'-deoxyribonucleoside derivatives that possess excellent reactivity for SNAr chemistry with a wide range of nucleophiles. Also, a benzotriazolyl nucleoside phosphoramidite appears to be a suitable reagent for incorporation into DNA for purposes of site-specific DNA modification.

Asymmetric Aza-Mannich Reactions of Sulfinimines: Scope and Application to the Total Synthesis of a Bromopyrrole Alkaloid

[reaction: see text] An asymmetric intermolecular aza variant of the Mannich reaction is reported utilizing chiral sulfinimine anions as the nucleophile and N-sulfonyl aldimines as the electrophilic component. A wide range of nucleophiles and electrophiles are tolerated by the reaction conditions, delivering the condensation products in good to excellent yield with a high degree of stereocontrol. Application of this methodology to the total synthesis of a natural product is reported.

A stereospecific ruthenium-catalyzed allylic alkylation.

Good regioselectivity and chirality transfer for aryl-substituted allyl units is achieved in allylic alkylations with a wide range of nucleophiles by using the highly active ruthenium catalyst 1. This method provides a route to antidepressants such as (−)-fluoxetine from (S)-ephedrine (see scheme; Cp*=η5-C5Me5, TBAT=tetrabutylammonium triphenyldifluorosilicate). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2002/z18496_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The ‘Eenie–Meenie reaction’. Displacement reactions of bisanilinopyrimidines

A novel acid-catalysed nucleophilic displacement reaction of pyrimidines is described, involving quinone–methide type chemistry. A wide range of nucleophiles can be tolerated. A similar mechanism is also applied to the synthesis of a tricyclic system.

Asymmetric Synthesis of β-Amino Acids by Addition of Chiral Enolates to Nitrones via N-Acyloxyiminium Ions

Abstract N-Acyloxyiminium ions, generated by the reaction of nitrones with acyl halides, are highly reactive species and undergo facile reaction with a wide range of nucleophiles, such as ketene silyl acetals, titanium(IV) and boron enolates, hydrido- and allyltin(IV) reagents, and alkynyltitanium(IV) reagents, to give α-substituted amine derivatives. Optically active β-amino acids can be prepared by the reaction of N-acyloxyiminium ions with both boron and titanium(IV) enolates bearing chiral auxiliaries. Reversal of diastereoselectivity was observed by the reactions of the boron and titanium(IV) enolates. Using these reactions, all of the four stereoisomers of α-methyl-β-phenylalanines, for example, can be prepared highly diastereoselectively. Cyclic N-acyloxyiminium ions are useful for the asymmetric synthesis of pyrrolidine and piperidine alkaloids; (5R,8R,8aS)-5-cyano-8-methylindolizidine, which is a common key intermediate for synthesis of 5-substituted 8-methylindolizidines, was prepared selectively.

The Synthesis and Chemistry of Formylphosphonate

New methods of synthesis and reactions of formylphosphonate have been investigated. Attempts to deprotect the corresponding diethyl acetal with TiIV halides led instead to the formation of halo(ethoxy)methylphosphonates which undergo substitution reactions with a wide range of nucleophiles. The products of reactions of formylphosphonate with bifunctional nucleophiles are determined in most cases by Baldwin's Rules, while the imines derived from formylphosphonate undergo Diels-Alder reactions only in those cases which carry a strongly electron-withdrawing N-substitutent.

The Synthesis and Chemistry of Formylphosphonate

New methods of synthesis and reactions of formylphosphonate have been investigated. Attempts to deprotect the corresponding diethyl acetal with TiIV halides led instead to the formation of halo(ethoxy)methylphosphonates which undergo substitution reactions with a wide range of nucleophiles. The products of reactions of formylphosphonate with bifunctional nucleophiles are determined in most cases by Baldwin's Rules, while the imines derived from formylphosphonate undergo Diels-Alder reactions only in those cases which carry a strongly electron-withdrawing N-substitutent.

Mark Efimovich Vol'pin: The path to science

Mark Efimovich Vol 'p in was born on May 23, 1923, in Simferopol into the family of doctors. The family often moved to new places, and Mark Efimovich learned Ukrainian and Turkmenian. From his early years, he showed interest in chemistry. In 1938, Vol 'p ins came in Moscow. At that time, a technical educational center for children was organized at the Polytechnic Museum; and young Vol 'p in enthusiastically started to study at the section of chemistry of this center. In 1939, he became a winner of the first Al l -Union Olympiad for young chemists and was admitted to the Department of Chemistry of the Moscow State University without entrance exams. He successfully completed the first year, but then his education was interrupted by the war. In 1941, M. E. Vol "pin vohmteered in the Army, but soon he was released because of health. During the three subsequent years he worked at the central chemical laboratory of the Ural tank construction plant in Miass (Chelyabinsk Region). These were hard and lean years; he had to work for 12--16 hours under conditions of almost no accident prevention. His lungs, injured during these years, told on him till the end of his life. At the Ural plant, M. E. Vol 'p in worked his way up from a laboratory assistant to deputy head of the laboratory, and introduced many new methods into analytical practice. The method for quick determination of tin in brot~zes developed by Mark Efimovich was presented at the All-Union competi t ion organized by the Ministry of Nonferrous Metallurgy, and was among the three best works. Only in 1945 did Vol 'p in return to the University. At that time, a s tudents ' scientific society was organized at the Department of Chemistry. A. F. Plat6, who was one of the guides of this society, became a teacher and a friend of Mark Efimovich for many years. A. F. Plat6 was the supervisor of M. E. Vo l ' p in ' s Ph.D. Thesis, entitled "Reactions of alkenes with ammonia in the presence of oxide catalysts; synthesis of acetonitrile" (1052). Ill 1953, M. E. Vol 'p in started to work in the Section of Theoretical Organic Chemistry at the AllUnion Institute of Scientific and Technical Information (VINITI). The Head of the Section, Dmitrii Nikolaevich Kursanov, highly appreciated Vol 'p in and invited him to carry out experimental research at his laboratory at the Institute of Organoelement Compounds of the USSR Academy of Sciences ( INEOS). In 1958, Vol 'p in joined the staff of this Institute. Owing to his work with D. N. Kursanov, who was a prominent scientist and a very cultured person of encyclopedic learning, ill a company of people enthusiastic about chemistry, Mark Efimovich quickly showed his talent, and very soon he obtained important scientific results. The subsequent scie~atific activity of Vol 'p in was entirely associated with the Institute of Organoelement Compounds. At this Institute, he accomplished his prominent works, which are recognized all over the world. The first studies of M. E. Vol 'p in were devoted to nonbenzenoid aromatic compounds. He had been interested in the problem of aromatici ty back in his student years. Vo l ' p in ' s fmldamental works dealing w i t h ' t h e chemistry of tropylium and cyclopropenylium cations are widely known.l He showed that the properties of the tropylium cation are determined, on the one hand, by the fact that it is a carbocation and, on the other:band, by the fact that it is an aromatic sys t em) As a carbenium ion, tropylium reacts with a wide range of nucleophiles, 3 whereas its aromatic nature accounts for its fairly high stability. Indeed, cycloheptatr ienylium cations are the most stable carbocations, able to exist in aqueous solutions. Since rotation of the seven-membered ring in the crystal precluded direct X-ray diffraction analysis o[" tropylium salts, 4 Vol 'p in proved the equivalence of all the C-C bonds in the tropylium cation using a ~4C isotope label. 5 Since the formation of an aromatic system is favorable, the C7H7 + cation is extremely easily generated upon cleavage of the C H , C--O, and C C

Transformation of organoiron complexes of synthetic and chemical interest

Abstract

Arylazo-glycenosides. Part IV. Synthesis and reactions of some 2- and 3-arylazo-derivatives of methyl 2,3-dideoxy-D-pent-2-enofuranoside

A method for the modification of some methyl D-pentofuranosidulose derivatives at the position α to the carbonyl group has been studied. Preparations are described of some new 2- and 3-phenylazo- and p-nitrophenylazoderivatives of methyl 2,3-dideoxy-D-pent 2-enofuranoside using D-xylose as the initial material. The procedures adopted for the syntheses are essentially those developed in our laboratories for the preparation of phenylazoderivatives of sugars and described in Part I.The new arylazo-derivatives have been shown to be useful synthetic intermediates: they undergo 1,4-addition reactions in a highly stereoselective way with a wide range of nucleophiles. For example, the following have been used in addition reactions, ammonia and dimethylamine, water, acetic acid, methoxide and azide ions, hydride and deuteride ions, and a range of sulphur nucleophiles. Structures of the products have been established by analysis of their n.m.r. spectra.A brief examination is reported of the formation of methyl D-pentofuranosiduloses carrying a substituent at position α to the carbonyl group from their arylhydrazones, which are the initial products of the addition reactions.

Arylazo-glycenosides. Part I. Synthesis and reactions of some 2- and 3-arylazo-derivatives of methyl 4,6-O-benzylidene-2,3-dideoxy-D-hex-2-enopyranosides

Preparations of the α- and β-anomers of methyl 2-O-benzoyl-4,6-O-benzylidene-D-ribo-hexopyranosid-3-ulose [(2) and (1)] and of methyl 3-O-benzoyl-4,6-O-benzylidene-D-ribo-hexopyranosidulose [(6) and (5)] are described. The phenylhydrazones [(12) and (28)] derivable from the α- and β-anomers of the 2-benzoate [(2) and (1)] have been converted by a base-catalysed elimination of benzoic acid into, respectively, the α- and β-anomers of methyl 4,6-O-benzylidene-2,3-dideoxy-3-phenylazo-D-erythro-hex-2-enopyranoside [(14) and (29)]. The phenylhydrazone (37) of the α-anomer of the corresponding 3-benzoate has likewise afforded the α-D-2-phenylazo-derivative (39).The 3-phenylazo-derivatives (14) and (29) have been shown to be useful synthetic intermediates: they undergo 1,4-addition reactions in a highly stereoselective fashion with a wide range of nucleophiles. For example, meth-oxide and azide ions, amines, acetic acid, and metal hydrides have each been added to the β-anomer (29), and 2-methoxyethoxide, methylmagnesium iodide, and the enolate derived from acetylacetone, as well as the aforementioned reagents, have been added to the α-form (14). Both these anomers gave 3-phenylhydrazones with the D-arabino- and D-ribo-structures: with the α-anomer a majority of the reagents afforded compounds with the D-arabino-configuration, whereas additions to the β-anomer usually afforded a product with the D-ribo-structure.The α-D-2-phenylazo-derivative (39) underwent addition reactions less readily: sodium borohydride was the only reagent found to add smoothly, to afford the phenylhydrazone (42) of a 3-deoxyhexoside in high yield. On the other hand use of sodium azide gave a poor yield of a 3-azido-product with the D-arabino-configuration. Sodium methoxide, however, did not add to the unsaturated system in compound (39): instead it induced rearrangement to yield methyl 4.6-O-benzylidene-3,4-dideoxy-α-D-glycero-hex-3-enopyranosid-2-ulose phenylhydrazone (41).Explanation of the differences in reactivity of these compounds and a rationalisation of the stereochemistry of the addition reactions are attempted.