Renato Dalpozzo

The reaction of vinyl grignard reagents with 2-substituted nitroarenes: A new approach to the synthesis of 7-substituted indoles

Abstract The reaction of three moles of vinylmagnesium bromide with one mole of nitroarene leads to the formation of indoles after aqueous work up of the mixture. Good yields are obtained with ortho -substituted nitroarenes.

Highly efficient and versatile acetylation of alcohols catalyzed by cerium(III) triflate

Cerium(III) triflate is a powerful catalyst for the acetylation of alcohols. The reaction works well for a large variety of simple and functionalized alcohols, without isomerisation of chiral centres. Changes of hydroxyl protective groups are possible in a one-pot procedure. The catalyst can be easily recycled.

Perchloric Acid and Its Salts: Very Powerful Catalysts in Organic Chemistry

5.3. Miscellaneous Electrophilic Reactions 3519 6. Protection and Deprotection Reactions 3519 6.1. Alcohols 3520 6.1.1. Esters 3520 6.1.2. Ethers 3522 6.2. Carbonyls 3523 6.2.1. Acetals 3523 6.2.2. Acylals 3524 6.2.3. 1,3-Dicarbonyls (Enol Ethers and Enaminones) 3525 6.2.4. Imines, Hydrazones, and Oximes 3525 6.3. Amines 3526 7. Three-Membered Ring Reactions 3526 7.1. Epoxides 3526 7.2. Aziridines 3528 7.3. Seleniranium Ion 3528 8. Ring Synthesis 3528 8.1. Four-Membered Rings 3528 8.2. Five-Membered Rings 3529 8.3. Six-Membered Rings 3533 8.4. Seven-Membered Rings 3539 8.5. Nazarov Reaction 3539 9. Miscellaneous 3540 9.1. Multicomponent Reactions (MCRs) 3540 9.2. Polymerizations 3542 9.3. Oxidations 3542 9.4. Carbonyl Activation 3543 9.5. Substitution Reactions 3545 9.6. Synthesis of Salts 3545 9.7. Ring-Opening Reactions 3546 10. Conclusion 3546 11. Abbreviations 3546 12. References 3546

Magnetic nanoparticle supports for asymmetric catalysts

The introduction of magnetic nanoparticles (MNPs) has favoured the recovery of catalysts with techniques of magnetic separation. Moreover, the small size of these functionalized particles becomes a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. Magnetite can be used as a support for catalytically active metals, decorated with ligands for metal complexes or with organocatalysts, which can be employed in green chemistry and pharmaceutically significant reactions. In particular, asymmetric metal complexes and enantiopure organocatalysts can lead to enantioenriched products and these reactions are summarized in this review.

Deprotection of t-butyldimethylsilyl ethers promoted by cerium(IV) triflate

t-Butyldimetylsilyl ethers are mildly cleft by catalytic amounts of cerium(IV) triflate. Dependence from water amount was observed.

A versatile route to β-enamino esters by acylation of lithium enamines with diethyl carbonate or benzyl chloroformate

Abstract A versatile route to β-enamino esters 1, using accessible starting materials, was developed. Lithiated enamines are allowed to react with diethyl carbonate or benzyl chloroformate with the formation of the β-enamino esters 1a or 1b. The reaction is rather general from a wide array of ketimines and aldimines. Products included cyclic β-enamino esters 1aa-ac, very useful for the synthesis of natural products.

Per-O-acetylation of sugars catalyzed by Ce(OTf)3

Ce(OTf)3 is proposed as a valuable Lewis acid promoter in the per-O-acetylation reactions of sugars. The Ce(OTf)3 is an environmentally friendly catalyst, used in very low percentage, and can be recovered after reaction and used without significant loss of activity.

9-Vinylguanine: an easy access to aza-analogs of 2′,3′-dideoxyguanosine

Abstract 9-Vinylguanine, obtained for the first time and fully characterised by X-ray analysis, allows access to aza-analogues of 2′,3′-dideoxynucleosides through cycloaddition processes.

Unexpected reactivity of allyl magnesium chloride with nitroarenes. A general method of synthesis of N-allyl-N-arylhydroxylamines and N-allylanilines

Abstract In contrast to alkyl Grignard reagents, the allyl reagent reacts with nitroarenes via 1,2 addition to the nitro group. The “in situ” treatment of the unstable intermediate adduct with LiAlH 4 in the presence of catalytic Pd/C provides a general synthesis of N-allyl-N-arylhydroxylamines or N-allylanilines.

Asymmetric Organocatalytic Reactions of α,β-Unsaturated Cyclic Ketones

The 1,4-conjugate addition of nucleophiles to α,β-unsaturated carbonyl compounds represents one fundamental bond-forming reaction in organic synthesis. The development of effective organocatalysts for the enantioselective conjugate addition of malonate, nitroalkane and other carbon and heteroatom nucleophiles to cycloenones constitutes an important research field and has been explored in recent years. At the same time, asymmetric Diels-Alder reactions have been developed and often a mechanism has been demonstrated to be a double addition rather than synchronous. This review aims to cover literature up to the end of 2010, describing all the different organocatalytic asymmetric 1,4-conjugate additions even if they are listed as transfer hydrogenation, cycloadditions or desymmetrization of aromatic compounds.