bluuebunny/crossref_metadata_2025_split huggingface dataset:
Problems of Innovation in Higher Education: The University of Brasília, 1961-1964
Authors: O'Neil Charles 
Published: March 2007

In the literature on Latin America, any increase in the number of people attending schools is usually considered economically and socially beneficial and a sign of progress. Any increase in the population attending universities is viewed as an especially important change and bound to help economic development. Rarely will any person or group argue that an increase in the number of university students is a drag on the economy and socially pernicious.Yet this is precisely the position taken by a small group within Brazil's Ministério de Educação e Cultura (MEC). Playing the role of a loyal but disgusted opposition, the Instituto Nacional de Estudes Pedagógicos (INEP) continuously attacked the educational policies of the federal and state governments during the 1950s, especially those relating to higher education.
The Comparative Focus in Latin American History
Authors: Genovese Eugene D. 
Published: March 2007

There are at least two reasons for United States and Latin American historians to bring their work together in a comparative thesis, the first being the need to maximize control of generalizations, and the second being the need to write the history of the social process by which a single world community has been developing since the sixteenth century. Recently, considerable progress with the first task has been made in the study of slavery and race relations, but little progress can yet be reported with the second.One result of the work on slavery and race relations ought to warn and encourage us. Without entering here into a discussion of the specific points of view advanced by Frank Tannenbaum, Marvin Harris, Sidney Mintz, Stanley Elkins, Gilberto Freyre, Herbert Klein, and so many others, it could be demonstrated that the comparisons of slavery in the United States, South America, and the Caribbean have so far proven enormously important in clarifying issues and stimulating new research and yet have failed to yield some of the most sought-after generalizations.
Intramolecular Reactions of Diazocarbonyl Compounds
Authors: Burke Steven D. , Grieco Paul A. 
Published: March 2007

Abstract
Since the demonstration by Stork and Ficini in 1961 that unsaturated diazoketones undergo intramolecular cyclization to form cyclopropanes the intramolecular reactions of α‐diazocarbonyl compounds have been extensively studied under thermal, catalytic, and photochemical conditions. Intramolecular cyclization of α‐carbonyl carbenes and carbenoids has found widespread application to the synthesis of theoretically interesting compounds such as bullvalene, twistane, bridged annulenes, and barbaralone, as well as syntheses of natural products such as sabinene, sirenin, α‐chamigrene, and phyllocladene. The reaction has also allowed the construction of several intriguing polycyclic systems that were unattainable by alternative methods.

A recent review has covered the reactions of diazoacetic esters with alkenes, alkynes, heterocyclics, and aromatic compounds. Unsaturated alkoxycarbonyl carbenes (:CHCO
2
R) and unsaturated carbonyl carbenes (:CHCOR) (where R contains either aromatic or olefinic groups), which are considered to be intermediates in the absence of catalyst, have been the subject of several other reviews. A review concerning photochemically, thermally, and catalytically induced Wolff rearrangements of α‐diazocarbonyl compounds has recently appeared. However to date no comprehensive review has appeared which demonstrates the synthetic potential of α‐diazocarbonyl insertion and addition reactions.

In reviewing the reactions of α‐diazocarbonyl compounds chosen not to include certain peripheral topics such as intermolecular reactions, intramolecular dimerization of bis(α‐carbonyl carbenoids) to give diacyl cycloolefins and intramolecular trimerizations of tris(α‐keto carbenoids), affording triacylcyclopropanes are not included. Also excluded are base‐catalyzed reactions of α‐diazocarbonyl compounds and certain ring‐contraction reactions involving CC bond insertion of intermediate α‐ketocarbenes.
The topics included in this report are the intramolecular reactions of α‐carbonyl carbenes and carbenoids with olefinic and aromatic unsaturation, with CH bonds, and with CC and NH single bonds. Also included are acid‐catalyzed cyclization reactions of α‐diazoketones.
Allylic and Benzylic Carbanions Substituted by Heteroatoms
Authors: Biellmann Jean‐François , Ducep Jean‐Bernard 
Published: March 2007

Abstract
This review covers allylic and benzylic carbanions in which a heteroatom and the double bond may be part of a conjugated system. Propargylic and allenic systems are also included. The cation is an alkaline or alkaline‐earth element; transition metals are excluded. The chapter by Gilman and Morton in 1954 was restricted to lithium derivatives. Reviews covering part of the subject include those on organometallic compounds, on reagents for nucleophilic acylation, on olefin synthesis with P(O)‐activated reagents, on the formation and reactions of carbanions derived from allylic sulfoxides, dithianes, nitrosoamines, thioethers and ethers, selenium compounds, on base‐catalyzed isomerization, and on rearrangements of carbanions.

Allylic and benzylic carbanions adjacent to the following
heteroatoms
have been described: boron, nitrogen, oxygen, silicon, phosphorus, sulfur, chlorine, selenium, bromine, tellurium.

The basicity and structures of these anions are considered first. This discussion is followed by sections on methods of generation of carbanions, reactions occurring during preparation, decomposition, and rearrangements of carbanions, reactions with electrophiles, regioselectivity and stereochemical aspects of the reactions, transformations of the reaction products, and some applications of these carbanions in synthesis.
TheFriedländer Synthesis of Quinolines
Authors: Cheng Chia‐Chung , Yan Shou‐Jen 
Published: March 2007

AbstractFriedländer prepared quinoline in 1882 by the condensation ofo‐aminobenzaldehyde with acetaldehyde in the presence of sodium hydroxide. This type of reaction has since been extensively explored and, in its most general form, can be defined as an acid‐ or base‐catalyzed condensation followed by a cyclodehydration between ano‐amino‐substituted aromatic aldehyde, ketone, or derivative thereof with an appropriately substituted aldehyde, ketone, or other carbonyl compound containing a reactive α‐methylene group. Some quinolines can also be prepared simply by heating a mixture of the reactants with or without a solvent.Because both reactants contain a carbonyl group, certain quinolines can be prepared from a single starting compound. Of historic interest is the formation of the dye flavaniline from acetanilide. When acetanilide is heated with zinc chloride, the acetyl group of some molecules migrates to theorthoposition, and that of others migrates to theparaposition. The resulting mixture ofo‐acetylaniline andp‐acetylaniline then undergoes Friedländer condensation to form flavaniline.Two related quinoline syntheses, the Pfitzinger reaction and the Niementowski reaction, can be considered as extensions of the Friedländer synthesis. The Pfitzinger reaction uses an isatic acid or isatin and the Niementowski reaction uses an anthranilic acid for condensation to form a 4‐quinolinecarboxylic acid and a 4‐hydroxyquinoline, respectively.Several other related reactions, such as the Combes quinoline synthesis, the Doebner–Miller quinoline synthesis, and the Skraup quinoline synthesis, use different types of starting compounds. It is of interest that all of the six aforementioned syntheses of quinolines were discovered within a period of 14 years in the latter part of the nineteenth century, undoubtedly reflecting many scientific interests and commercial activities at that time, including the isolation of quinolines from coal tar, the manufacture of dyes, and studies of natural products such as alkaloids.
Replacement of Alcoholic Hydroxyl Groups by Halogens and Other Nucleophiles via Oxyphosphonium Intermediates
Authors: Castro Bertrand R. 
Published: March 2007

Abstract
The Michaelis–Arbuzov reaction involves the formation of dialkyl alkylphosphonates by heating alkyl halides with trialkyl phosphites, via an intermediate phosphonium salt. In recent years it has been found that phosphonium salts can be formed by reaction of a variety of trivalent phosphorus compounds with oxidizing electrophiles, and that the resulting phosphonium intermediates can be trapped with an alcohol to form alkoxyphosphonium cations. These cations can then undergo nucleophilic displacements, either with their own counterions or with added nucleophiles.

This chapter is limited to species formed
in situ
from trivalent phosphorus compounds and various oxidants. The most commonly used trivalent phosphorus compounds are triphenyl phosphite, triphenylphosphine, and tris(dimethylamino)phosphine. The most commonly used oxidants are molecular halogens, alkyl halides, carbon tetrahalides,
N
‐haloamides,
N
‐haloamines, and diethyl azodicarboxylate (DEAD). Other oxidants that have been used include mercuric salts, peroxides, dithioesters, and sulfenamides. The more common combinations of phosphorus(III) compounds and oxidants are summarized.

The replacement of hydroxyl groups by halogen, the most common use of oxyphosphonium intermediates, is the principal subject of this chapter. However, the replacement of hydroxyl groups by oxygen, nitrogen, sulfur, and carbon nucleophiles is also discussed. This review is restricted to alcoholic hydroxyl groups, and does not include a discussion of carboxylic hydroxyl groups.
The principal combinations covered are triphenylphosphine–diethyl azodicarboxylate, triphenyl phosphite–methiodide, triphenylphosphine–halogen, triphenylphosphine–tetrahalomethane, triphenylphosphine–N‐haloimide, and tris(dimethylamino)phosphine–tetrahalomethane. Some of these combinations have been discussed in recent reviews.
Reductive Dehalogenation of Polyhalo Ketones with Low‐Valent Metals and Related Reducing Agents
Authors: Noyori Ryoji , Hayakawa Yoshihiro 
Published: March 2007

Abstractα‐Halo ketones play a significant role in organic synthesis because of their ready availability and the diversity of their chemical reactions, which reflect the various functionalities in the molecule,viz., a reactive halogencarbon bond, acidic hydrogen atoms, and a carbonyl moiety. An important reaction of halo ketones is removal of the halogen atom(s) by low‐valent transition metals and related reducing agents to generate reactive species that are capable of undergoing carboncarbon bond‐forming reactions. The cyclocoupling reactions of α,α′‐dihalo or more highly halogenated ketones across 1,3‐dienic or olefinic substrates to give seven‐ or five‐membered ketones, respectively, are especially noteworthy from the synthetic viewpoint.The direct preparation of odd‐membered carbocycles has remained a persistent problem, and until recently only a few methods of synthesis were available. The existing methods for obtaining seven‐membered carbocycles have been limited to expansion of six‐membered rings and certain cyclization reactions. The construction of five‐membered carbocyclic systems has generally been accomplished only by intramolecular condensation of open‐chain dicarbonyl compounds or dicarboxylic acid derivatives, ring contraction of six‐membered cyclic ketones, or ring expansion of four‐membered cyclic ketones. These methods, however, are not always useful because of the limited availability of the starting materials in certain reactions. In principle the most direct method for construction of seven‐membered carbocycles is the cyclo‐condensation between three‐carbon and four‐carbon units,viz., 1,3‐dienes, for preparation of five‐membered carbocycles, the combination of three‐carbon and two‐carbon units,viz., olefinic substances, or one‐carbon and four‐carbon units, respectively, can be considered. However, these reactions are not achieved easily because of the difficulty of generating reactive three‐carbon and one‐carbon units that are capable of undergoing cycloaddition across the unsaturated substrates. Reactions of low‐valent metals and α,α′‐dihalo or more highly halogenated ketones generate such bifunctional three‐carbon species that can enter into both types of cycloaddition reactions. Moreover, these reactive species also undergo [3 + 2] cycloadditions across certain unsaturated bonds containing heteroatoms, thereby giving rise to five‐membered heterocycles. Thus these [3 + 4] and [3 + 2] annulations have allowed easy access to a wide range of organic frameworks that are of theoretical or practical importance. The scope and limitations of these cyclocoupling reactions and their synthetic applications are the main concern of this chapter, which briefly describes other examples of dehalogenation of α‐mono‐ and α,α′‐polyhalo ketones using low‐valent transition metals and related reducing agents. Also described are the mechanistic aspects of the reductions and several representative experimental procedures.
ThePasserini Reaction
Authors: Banfi Luca , Riva Renata 
Published: March 2007

AbstractIsocyanides are a very special class of organic compounds, which may behave as acyl anion equivalents. However, with very few exceptions, isocyanides do not react with carbonyl compounds in the absence of an acid. In this chapter, all reactions of a carbonyl compound or an acetal with an isocyanide are considered. These are processes that frequently, but not invariably, result in the incorporation of an acid residue in the final product. In the classic Passerini reaction, discovered in 1921 by Mario Passerini, the acid is always a carboxylic acid and the products alpha‐acyloxy amides. A more recent variation, which is often referred to as the Passerini reaction as well, employs a variety of mineral (H+) or Lewis acids (LA) to afford alpha‐hydroxy amides. These compounds may also be formed in the presence of carboxylic acids such as formic acid or trifluoracetic acid. Interactions of isocyanides with carbonyl compounds and some protic or Lewis acids can also lead to a large variety of products other than alpha‐hydroxy amides, including several heterocyclic systems. These Passerini‐type reactions are discussed. Acetals can also react with isocyanides in the presence of Lewis acids. The usual products are alpha‐alkoxy amides.The classic Passerini reaction is one of the oldest multicomponent reactions and is the first based on isocyanides to be discovered. This method is experiencing a growing interest. Its scope has been expanded by employing bifunctional substrates able to undergo secondary reactions. In this way, a larger variety of products can be synthesized and complex biologically active substances can be accessed quickly. Modifications that form products different from alpha‐acyloxy amides or alpha‐hydroxy amides, especially those leading to heterocycles, may find useful applications in synthesis.
The Allylic Trihaloacetimidate Rearrangement
Authors: Overman Larry E. , Carpenter Nancy E. 
Published: March 2007

AbstractSigmatropic rearrangements of allylic systems have found wide application in organic synthesis, with carbon‐carbon bond forming rearrangements such as the Cope and Claisen rearrangements being particularly well known. The sigmatropic rearrangement of allylic imidates offers a valuable entry into the preparation of protected allylic amines. Conversion of an imidate to the amide is essentially irreversible, with the transformation of the imidate to the amide being exothermic by about 15 kcal/mol. Since the discovery of the thermal allylic imidate rearrangement in 1937, a number of systems have been investigated for the practical preparation of allylic amines by this route. However, it was the discovery and development of the rearrangement of allylic trichloroacetamidates that demonstrated the utility of this synthetic method.This chapter is limited to the discussion of allylic trichloro‐ and trifluoracetamidate rearrangements. The [3,3]‐sigmatropic rearrangement of trichloracetamidates (now called the Overman rearrangement) or trifluoroacetimidates can be carried out either thermally or with Hg(II) or Pd(II) catalysis, The scope of this rearrangement is such that primary, secondary, and tertiary allylic amides are readily accessible, thus providing a wide entry into nitrogen‐containing products such as amino sugars, nucleotides, peptides, etc. The Overman rearrangement has found extensive application in the total synthesis of natural products. The recent development of the use of chiral Pd(II) catalysts bodes well for amine synthesis.
Asymmetric Dihydroxylation of Alkenes
Authors: Noe Mark C. , Letavic Michael A. , Snow Sheri L. 
Published: March 2007

Abstract
The oxidation of alkenes to vicinal diols using osmium tetroxide is one of the most selective and reliable transformations in organic synthesis. The reaction stereospecifically produces a cis‐1,2‐glycol and is tolerant of a wide array of functional groups. Methods have been developed to oxidize alkenes stoichiometrically, as well as in the presence of catalytic amounts of osmium tetroxide, when a suitable secondary oxidant is present. The latter process is particularly useful considering the expense and toxicity of osmium tetroxide. The utility of dihydroxylation in organic synthesis is enhanced by the facile transformations of the cis‐1,2‐diol products into other useful derivatives. Among the most versatile intermediates are the corresponding cyclic sulfates, which serve as reactive epoxide equivalents that can be used singly or doubly displaced with amine‐, oxygen‐, sulfur‐, or carbon‐based nucleophiles.
The reaction of osmium tetroxide with alkenes is accelerated by several orders of magnitude in the presence of coordinating amine ligands such as triethylamine, quinuclidine, or diazobicyclooctane. The logical extension to asymmetric osmylation of alkenes in the presence of chiral amine bases spurred the study of asymmetric dihydroxylation. The breakthrough of catalytic turnover in the cinchona alkaloid‐osmium tetroxide system revolutionized the field of asymmetric dihydroxylation. Specialized ligands have been developed to provide position selectivity in the dihydroxylation of polyenes, efficient kinetic resolution of racemic substrates, and high levels of enantioselectivity for each of six alkene classes.
Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes
Authors: Uemura Motokazu 
Published: March 2007

AbstractThis chapter covers reactions of (η6‐arene) chromium complexes that occur in the side chain of the arene, and reactions that exhibit stereocontrol as a result of complexation. Reactions that focus on nucleophilic additions to the chromium‐coordinated aromatic ring and on directed lithiation of the arene ring are not covered.The tricarbonyl(η6‐arene) complexes are readily prepared by several convenient methods, and these complexes are relatively stable to air and moisture. Most arenes will coordinate to the tricarbonyl fragment. Certain functional groups are incompatible and electron withdrawing groups, such as CHO and CO2H, retard complexation. Protection of these functional groups as acetals or esters followed by chromium complexation and hydrolysis procedures give the corresponding tricarbonylchromium complexes of benzaldehyde or benzoic acid in good yields. Electron‐donating substituents accelerate the rate of complexation. The chemical consequences of chromium complexation include (1) the activation of the aromatic ring to nucleophilic addition; (2) enhancement of acidity in the side chain; (3) enhancement of the rate of solvolysis in the side chain; (4) enhancement of acidity of aromatic hydrogens: (5) control of reactions by steric effects of the tricarbonylchromium fragment. After the reaction, the tricarbonylchromium fragment can be easily removed by mild oxidation. When the arene ring is disubstituted with different substituents at the ortho and meta positon, the complexes are planar chiral and the substrates are useful for asymmetric synthesis.
Phylogeography and population structure of the golden monkeys (Rhinopithecus roxellana): inferred from mitochondrial DNA sequences
Authors: Li Ming , Liu Zhijin , Gou Jinxun , Ren Baoping , Pan Ruliang , Su Yanjie , Funk Stephan M. , Wei Fuwen 
Published: March 2007

AbstractThe golden monkey (Rhinopithecus roxellana) is one of the most endangered primate species due to its dramatically shrinking distribution during the past 400 years. Its populations are restricted to three isolated regions, Qinglin (QL), Sichuan/Gansu (SG), and Shennongjia (SNJ) in China. As with other snub‐nosed monkeys in China and Vietnam, the biology and evolution of this species is still poorly known. To assess genetic differentiation and explore the relationships among populations of golden monkeys from different geographic locations, 379 bp of mitochondrial DNA control region (CR) hypervariable segment I (HVI) was studied from 60 individuals. Twelve haplotypes were identified from seven populations within the three regions. Haplotype diversity was high (0.845), whereas nucleotide diversity among all haplotypes was low (0.0331). The most recent common ancestor (TMRCA) among mtDNA haplotypes was estimated to have lived approximately 0.48–0.32 million years ago. None of the haplotypes is shared among any of the three regions. Phylogenetic analysis and AMOVA revealed clear and significant phylogeographic structure between the three regions. However, only SG contained haplotypes of the two main clades, indicating either incomplete random sorting of haplotypes or a complex history with phases of population subdivisions and merging of populations. The phylogeographic structure implies that R. roxellana should be regarded as separate management units (MUs) for each of the three regions. It is likely that recent phylogeographic history has shaped the pattern of genetic differentiation observed in the golden monkey and that its populations have suffered significant demographic fluctuation. Am. J. Primatol. 69:1195–1209, 2007. © 2007 Wiley‐Liss, Inc.
The link‐prediction problem for social networks
Authors: Liben‐Nowell David , Kleinberg Jon 
Published: March 2007

AbstractGiven a snapshot of a social network, can we infer which new interactions among its members are likely to occur in the near future? We formalize this question as the link‐prediction problem, and we develop approaches to link prediction based on measures for analyzing the “proximity” of nodes in a network. Experiments on large coauthorship networks suggest that information about future interactions can be extracted from network topology alone, and that fairly subtle measures for detecting node proximity can outperform more direct measures.