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Allylic oxidations of olefins to enones are C–H functionalizations and are valuable organic transformations that permit the synthesis of value-added products from simple precursors. A variety of stoichiometric and catalytic metal-based methods are available for these conversions. In addition, metal-free and biocatalytic protocols are gaining in importance. This review summarizes the available oxidation methods and compares their regio- and chemoselectivities. 1 Introduction 2 Chromium-Based Oxidation 2.1 Stoichiometric Methods 2.2 Catalytic Methods 2.3 Chromium on Solid Support 3 Regio- and Chemoselectivity of Allylic Oxidations 4 Other Metal-Based Oxidations 4.1 Copper Reagents 4.2 Rhodium Reagents 4.3 Selenium Reagents 4.4 Cobalt Reagents 4.5 Ruthenium Reagents 4.6 Palladium Reagents 4.7 Iron Reagents 4.8 Other Metal Reagents 5 Metal-Free and Biocatalytic Methods 5.1 Metal-Free Methods 5.2 Biocatalytic Methods 6 Conclusion

Due to its rigid cage structure, adamantane has received considerable interest as a scaffold with a defined tetrahedral geometry. In this paper we describe orthogonally functionalized tetrasub­stituted adamantane derivatives. These compounds may be conjugated to other functional molecules by standard techniques such as amide formation or click chemistry and are thus useful (3 + 1) scaffolds for medicinal and material chemistry.

We present a review of different methods for the preparationof five- and six-membered cyclic hydrazino α-carboxylic acids- andtheir derivatives. These heterocycles are common building blocksin pharmaceuticals and many natural products. In addition, hydrazinocarboxylic acids have been used as auxiliaries and intermediatesin organic syntheses and selected applications are highlighted inthis summary. For six-membered heterocycles (piperazic acids), theliterature since 1998 is covered as a follow-up to the review byCiufolini and Xi. 1 Introduction 2 Synthesis of Five-Membered-Ring Systems 2.1 [3+2] Cycloadditions 2.2 Cyclization of N-Acyl HydrazoniumIons 2.3 [4+2] Cycloadditions 2.4 Tandem and Multicomponent Syntheses 3 Synthesis of Six-Membered-Ring Systems 3.1 Hetero-Diels-Alder Reactions 3.2 Cyclization via Nucleophilic Displacement 3.3 Intramolecular N-Arylation 3.4 Intramolecular Hydrazone Formation 3.5 Intramolecular Lactam Formation 3.6 Ring-Closing Metathesis 4 Summary

This review focuses on recent synthetic developments for the stereoselective preparation of aza- and diazabicyclo[X.Y.O]alkane dipeptide mimetics of the general structures 1-3. Different synthetic strategies are compared with respect to stereoselectivity as well as flexibility regarding ring sizes, stereochemistry and introduction of side-chains.