Previous Reviews

Since the first reported structure elucidation applications of HMBC at natural abundance that appeared in the mid 1990s, a burgeoning number of reports have appeared, which have in turn engendered a number of reviews. The majority of the reviews that have appeared thus far have focused on general applications of the HMBC experiment or 

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As apparent from the contributing resonance structures, both mesoionic systems contain an azomethinylide contribution, accounting for the reaction with representative dipolarenophiles to give cycioadducts such as 3 or 4 (Scheme 4). The cydoadditions and extrmsion reactions of the adducts have been the mam object of investigation. since previous reviews on me.soionic thiazoles (2.9V Results appearing since 1969 and before June 1976 are reported for each type of compound in this chapter. Tables VIIRl-5 contain all mesoionic thiazoles described before June 1976. 

Previous reviews on silicones in relation to adhesion have dealt with specific technologies such as adhesives, sealants, and coupling agents [12-17]. This review attempts to address the fundamental properties of silicones and to relate them to various aspects of adhesion technologies. The perspective taken in this review is from the point of view of a newcomer in the field of adhesion and silicones. 

A record of any outstanding corrective actions from previous reviews... 

Catalytic hydrogenation has been utilized extensively in steroid research, and the method has been found to be of great value for the selective and stereospecific reduction of various functional groups. A number of empirical correlations concerning selectivity and product stereochemistry compiled for steroid hydrogenations has been listed in a previous review. ... 

Because of thetr electron deficient nature, fluoroolefms are often nucleophihcally attacked by alcohols and alkoxides Ethers are commonly produced by these addition and addition-elimination reactions The wide availability of alcohols and fliioroolefins has established the generality of the nucleophilic addition reactions The mechanism of the addition reaction is generally believed to proceed by attack at a vinylic carbon to produce an intermediate fluorocarbanion as the rate-determining slow step The intermediate carbanion may react with a proton source to yield the saturated addition product Alternatively, the intermediate carbanion may, by elimination of P-halogen, lead to an unsaturated ether, often an enol or vinylic ether These addition and addition-elimination reactions have been previously reviewed [1, 2] The intermediate carbanions resulting from nucleophilic attack on fluoroolefins have also been trapped in situ with carbon dioxide, carbonates, and esters of fluorinated acids [3, 4, 5] (equations 1 and 2)... 

The AE reaction has been applied to a large number of diverse allylic alcohols. Illustration of the synthetic utility of substrates with a primary alcohol is presented by substitution pattern on the olefin and will follow the format used in previous reviews by Sharpless but with more current examples. Epoxidation of substrates bearing a chiral secondary alcohol is presented in the context of a kinetic resolution or a match versus mismatch with the chiral ligand. Epoxidation of substrates bearing a tertiary alcohol is not presented, as this class of substrate reacts extremely slowly. 

The reader is referred to previous reviews for historical aspects and early work. For condensed quinazoline systems, The Chemistry of Heterocyclic Compoundsr—Six Membered Heterocyclic Nitrogen Compounds with Four Condensed Rings should be consulted. 

The pyridopyrimidines discussed in this review are derived by the ortho fusion of the pyridine and pyrimidine rings through ring carbon atoms. There are four such compounds for which the nomenclature and numbering of Chemical Abstracts (1-4) will be used. Alternative names used in the literature are 1,3,8-triazanaphthalene (1), 1,3,5-tri-azanaphthalene (2), 1,3,7-triazanaphthalene or copazoline (3), and 1,3,6-triazanaphthalene (4). There has been no previous review of the... 

The use of dipole moments (dielectric constant method) shows a considerable decline from the time of our previous review (76AHCSl).The technique is time consuming and the progress in instrumentation has not been great. Moreover, the method is unsuitable when more than two tautomers are present. Although dipole moments are easily computed (see Section III,D), most theoreticians think that only gas-phase values (from MW spectroscopy, see Section VII,A) are useful to check the calculated values. 

On the whole, the four main changes from the previous review (76AFICS1) have been (1) the standard application of high-level theoretical methods, (2) the massive use of X-ray crystallography, (3) the introduc-... 

At the time of the previous review (76AHCS1), 3//-indole was unknown. Reeently it was found that this eompound is formed when an etheral solution of 2,3-dihydro-A-indolylaeetophenone is irradiated at 308 or 313 nm... 

As already mentioned in the previous review (76AHCS1, p. 246), potential 2,3-dihydroxypyrroles exist in the monoenol form 132. Recent work has confirmed these observations (76LA476 94MI5). 

Tautomerism of [6.6]biheterocycles was not covered in the previous review (76AHCS1). Since then, several surveys appeared on pyrazino[2,3-djpyrimidines or pteridines (135) with some coverage of tautomerism, with the most recent by Pfieiderer [96CHEC(7)679, and references therein],Tire results on pteridines not included in the previous surveys, are discussed in this section. Limited data on other heterocycles are also covered. 

Once an electron-withdrawing group is introduced onto the indole nucleus, no matter which position it is, 1-hydroxyindoles become stable (91YGK205, 99H1157). For the preparation of such stable 1-hydroxyindoles, various reagents and conditions can be employed and many approaches have been reported, as summarized in previous reviews (79MI1, 90AHC105). 

Methylation of 1-hydroxyindoles can be achieved readily by the reaction with diazomethane, Mel, orMc2S04 in the presence of an appropriate base, as described in previous reviews (79MI1, 90AHC105, 91YGK205, 99H1157). Alkylation and acylation also work well with alkyl halides, acyl halides, acid anhydrides, and acids in the presence of acid activators such as DCC and so on. 

In the previous review (91YGK205, 99H1157), we reported that l-hydroxy-4-nitroindole forms active ester derivatives by reaction with carboxylic acids, which can be applied to acylation of various nucleophiles. To expand the scope of the reaction and obtain novel fungicidal compounds, an attempt has been made to prepare derivatives of wasabi phytoalexin 109 (98P1959). 

As noted in the previous review (99H1157), we proposed a working hypothesis that 1-hydroxyindoles are classified into two groups from the point of reactivity characteristics toward 85% HCOOH (Scheme 34). Thus, type 1 compounds 227... 

The aim of the present review is to report in broad outline the progress in quinoxaline chemistry since about 1956 previous reviews of the quinoxaline literature are to be found in three major reference... 

Previous reviews on the chemistry of isoxazole dealt primarily with the synthetic routes and the nucleophilic cleavage of isoxazole derivatives. The first part of the present review is concerned with new investigations in the synthetic field, but the main attention is devoted to a study of the properties of isoxazoles. The review covers studies undertaken during this decade though some earlier works are mentioned when necessary. No complete coverage of the chemistry of partly or fully reduced isoxazoles and their oxo derivatives is attempted, but those aspects of the chemistry of isoxazolines and isoxazolidines that are closely related to the problems under discussion are also mentioned. 

No data on the tautomerism of dihydro-1,2,4-triazines were available at the time of the previous reviews [76AHCS1 85AHC(38)1, p. 83] since then, however, much work has been done. For N-unsubstituted dihydro-1,2,4-triazines, nine possible isomers (92-100) could exist however, only some of them (92-95, 98, and 99) have been synthesized individually. 

Sometimes two discharge voltage plateaus are seen on nickel oxide electrodes. Early observations are documented in previous reviews [2, 9]. Normally, nickel oxide electrodes have a voltage plateau on discharge in the potential range of 0.25-0.35V vs. Hg/HgO. The second plateau, which in some cases can account for up to 50% of the capacity, occurs at -0.1 to - 0.6 V. At present there is a general consensus that this second plateau is not due to the presence of a new, less-active, compound [91-94]. Five interfaces have been identified for a discharging NiOOH electrode [93]. These are... 

In the tradition of previous reviews [1-22], this section addresses various aspects of nonaqueous electrolytes, including intrinsic properties, such as local structures caused by ion-ion and ion-solvent interactions and bulk properties, such as ionic conductivity, viscosity, and electrochemical stability (voltage window), and their relationships to intrinsic properties. 

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