Reaction mechanisms heterocyclic chemistry

Chemistry, reaction mechanisms, and properties have been extensively reviewed.4,5,10-20 Hie present chapter deals witii only one type of fully cyclized aromatic heterocyclic polymers die high-molecular-weight linear polymer witii a special emphasis on die synthesis and structure—property relationships for specific applications. 

Organic Compounds of Sulphur, Selenium, and Tellurium Radiochemistry Reaction Kinetics Saturated Heterocyclic Chemistry Statistical Mechanics Surface and Defect Properties of Solids Terpenoids and Steroids Theoretical Chemistry... 

Inorganic Chemistry of the Main-group Elements Inorganic Chemistry of the Transition Elements Molecular Spectroscopy Molecular Structure by Diffraction Methods Radiochemistry Reaction Kinetics Saturated Heterocyclic Chemistry Statistical Mechanics... 

As with any potential energy surface calculation, it is important that a sufficient level of theory is used in order to get reliable information about reaction mechanisms in heterocyclic chemistry. Molecular mechanics has been used extensively to calculate the endpoints of these reactions and to afford information about thermodynamic control and relief of strain, but the technique is not suited to the general study of transition structures. Semiempirical approaches have found wide application but a cautious user would compare the results with higher-level calculations or experimental observations. Although often successful, at least one study has found limitations in the semiempirical methods for heterocycles containing N-N bonds. ... 

Since then, the fundamental physicochemical aspects of the synthesis and properties of ev anines have been exhaustively reviewed by Heseltine and Stunner in the fourth edition of Mee s treatise (3) and by Sturmer in Weissberger s edition of the Chemistry of Heterocyclic Compounds (4). So the purpose of this section dealing especially with thiazolomethine dyes is to give, apart from a complete and recent list of dyes and references, a description of the particularities of their chemistry and chiefly of the reaction mechanisms involved in their synthesis that have remained unknown or have not been discussed until now. 

As is common in heterocyclic chemistry, many studies concern tautomeric equilibria. While quantum chemical calculations are straightforward for the question of the most stable isomer, experiments are sometimes very demanding. Therefore, quantum chemistry can easily provide answers that may require substantial experimental effort. Comparatively few studies concern the investigation of entire reaction paths. This is much more demanding than computing a limited number of tautomers, of course, but usually provides a very detailed picture of the reaction mechanism. In certain cases, it was only possible to judge the nature of a chemical reaction on the basis of quantum chemical calculations. 

MATHEY Phosphorus-Carbon Heterocyclic Chemistry The Rise of a New Domain McKILLOP Advanced Problems in Organic Reaction Mechanisms OBRECHT Solid Supported Combinatorial and Parallel Synthesis of Small-Molecular-Weight Compound Libraries... 

The Heck reaction, first disclosed by the Mori and Heck groups in the early 1970s [65, 66], is the Pd-catalyzed coupling reaction of organohalides (or triflates) with olefins. Nowadays, it has become an indispensable tool for organic chemists. Inevitably, many applications to heterocyclic chemistry have been pursued and successfully executed. In one case, Ohta et al. reacted 2-chloro-3,6-dimethylpyrazine (49) with styrene to furnish ( )-2,5-dimethyl-3-styrylpyrazine (50) [67]. Here, only the E isomer was observed. The outcome will become apparent during the ensuing discussions on the mechanism. 

Nucleophilic substitutions are in many cases facile processes in heterocyclic chemistry. Also, in the area of the present chapter, many such routine transformations have been carried out. Such transformations are summarized in Table 6, where the structures of the starting compounds, products, the reagents, yields, and references are listed. These include reactions of halogen, methoxy, and methylsulfanyl derivatives with amines or alkoxides. One exceptional case (Table 6, entry 9) should be pointed out this exchange reaction, unlike the others in this table, proceeds via an elimination-addition mechanism. A few related transformations that follow more complicated pathways and therefore could not be classified unambiguously into this table, can be found in Table 7 in Section 11.17.5.6.5. 

Yvette Jackson, a Jamaican, graduated with a BSc (special) degree in chemistry (1976), and a PhD in chemistry (1983), from the University of the West Indies, Mona campus (UWI, Mona). Her PhD work, under the supervision of Dr. Vernon G. S. Box, involved synthesis of rotenoids -oxygen heterocycles popularly known for their insecticidal activity. She joined the staff at UWI, Mona, in 1983 as an assistant lecturer. Since then she has done postdoctoral work (1986) and many collaborative summer research stints with Prof. Michael P. Cava and Dr. M. V. Lakshmikantham at the University of Alabama, Tuscaloosa, USA, and has risen up the ranks to professor at the University of the West Indies. Her research interests are in the areas of synthetic organic chemistry and organic reaction mechanisms. 

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