Reactivity-selectivity Synthesis

Throughout each chapter, clear structures, schemes, and figures accompany the text. Mechanism, reactivity, selectivity, and stereochemistry are especially addressed. Special emphasis is also placed on introducing both the logic of total synthesis and the rationale for the invention and use of important synthetic methods. In particular, we amplify the most important developments in asymmetric synthesis, catalysis, cyclization reactions, and organometallic chemistry. 

A wide range of ring sizes have been synthesized, from the very small [1.1.0] fused ring systems to the macro-bicyclic systems. The reactivity and synthesis of the fused ring systems is reviewed first followed by the nonfused compounds. As the synthetic methods used to produce the various examples in this class of compounds were well reviewed in CHEC-II(1996), the synthetic methods section, Section 12.12.8, will outline selected types of compound within this group that have received more attention over the review period. 

Allylzirconocene derivatives are reactive toward aldehydes, presumably because of the availability of six-centered transition states permitting an anti-selective synthesis of homo-allyl alcohols (Scheme 1.27) [115]. 

The reactions described show that sulfur monochloride is an important reagent for the synthesis of heterocycles with various numbers of sulfur atoms and even without sulfur. An important feature of this reagent is that it can add not only two sulfur atoms to the molecule, as might be expected, but also one, three, four, five or even more atoms, and the structure of the final compound often depends on its stability. Recent developments in the use of sulfur monochloride include the discovery of its ability to form complexes with organic bases and of the significant difference in reactivity of these complexes from S2CI2. A selective synthesis of particular heterocycles requires accurate conditions (temperature, solvent, catalyst and base). 

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