Enantioselective Diamination with Novel Chiral Hypervalent Iodine Catalysts

Vicinal diamines constitute one the most important functional motif in organic chemistry because of its wide occurrence in a variety of biological and pharmaceutical molecules. We report an efficient metal‐free, highly stereoselective intramolecular diamination using a novel chiral hypervalent iodine reagent together with its application as an efficient catalyst for the synthesis of diamines.     

Flexible Stereoselective Functionalizations of Ketones through Umpolung with Hypervalent Iodine Reagents

The functionalization of carbonyl compounds in the α‐position has gathered much attention as a synthetic route because of the wide biological importance of such products. Through polarity reversal, or “umpolung”, we show here that typical nucleophiles, such as oxygen, nitrogen, and even carbon nucleophiles, can be used for addition reactions after tethering them to enol ethers. Our findings allow novel retrosynthetic planning and rapid assembly of structures previously accessible only by multistep sequences.     

Organocatalytic Oxidative Annulation of Benzamide Derivatives with Alkynes

Organocatalytic annulation by functionalization of benzamide derivatives with alkynes has been developed. We report a new approach of cycloaddition under mild reaction conditions using simple catalysts, such as iodobenzene and peracetic acid, as oxidant. Those novel, mild reaction conditions provided a straightforward synthesis of isoquinolones with fast reaction rate. Notable selectivity in annulation of unsymmetrically disubstituted alkynes was demonstrated.     

Inside back cover: highly stereoselective metal-free oxyaminations using chiral hypervalent iodine reagents (angew. Chem. Int. Ed. 14/2012)

About 30?% of the world's iodine production comes from the Chiba area in Japan, shown in the background of the picture (Map data (?) 2012 ZENRIN Imagery (?) 2012 TerraMetrics). Enantiomerically pure hypervalent iodine compounds are the key for metal-free, highly stereoselective oxyaminations of alkenes. In their Communication on page?3462?ff., T. Wirth and U. Farid report the use of the reaction for the facile synthesis of 2-arylprolinols.     

Highly stereoselective metal-free oxyaminations using chiral hypervalent iodine reagents

The ring and I: Hypervalent iodine compounds avoid the issues of toxicity or complicated ligands of many transition-metal-based systems. A highly enantioselective oxyamination of alkenes with N-sulfonyl ureas employing chiral, lactic acid-based hypervalent iodine reagents gives a facile synthesis of enantiomerically pure 2-arylproline derivatives for the first time.     

A Triazole‐Substituted Aryl Iodide with Omnipotent Reactivity in Enantioselective Oxidations

A widely applicable triazole‐substituted chiral aryl iodide is described as catalyst for enantioselective oxidation reactions. The introduction of a substituent in ortho‐position to the iodide is key for its high reactivity and selectivity. Besides a robust and modular synthesis, the main advantage of this catalyst is the excellent performance in a plethora of mechanistically diverse enantioselective transformations, such as spirocyclizations, phenol dearomatizations, α‐oxygenations, and oxidative rearrangements. DFT‐calculations of in situ generated [hydroxy(tosyloxy)iodo]arene isomers give an initial rational for the observed reactivity.     

The Stereoselective Synthesis of Indoloquinolizines

Carboline was reduced with lithium aluminum hydride to provide carboline-alcohol whichreacted with methyl vinyl ketone to form the corresponding hydroxymethyl-amino-ketone. Underphase transfer condition it can be converted into enantiomerically pure indoloquinolizines. The cycliza-tion mechanism was also illustrated here.     

Asymmetric Organocatalytic Rearrangement Reactions

Rearrangement reactions often lead to the regio‐ and stereoselective formation of carbon–carbon or carbon–heteroatom bonds, and allow the construction of otherwise hard‐to‐access molecular frameworks. Research disclosed in the present decade, especially in the last two years, has shown that organocatalytic modes of activation can be successfully applied to a variety of rearrangements. In this Minireview we discuss the advances achieved so far in asymmetric organocatalytic rearrangement reactions.     

Hypervalent Iodine‐Catalyzed Oxidative Functionalizations Including Stereoselective Reactions

Hypervalent iodine chemistry is now a well‐established area of organic chemistry. Novel hypervalent iodine reagents have been introduced in many different transformations owing to their mild reaction conditions and environmentally friendly nature. Recently, these reagents have received particular attention because of their applications in catalysis. Numerous hypervalent iodine‐catalyzed oxidative functionalizations such as oxidations of various alcohols and phenols, α‐functionalizations of carbonyl compounds, cyclizations, and rearrangements have been developed successfully. In these catalytic reactions stoichiometric oxidants such as mCPBA or oxone play a crucial role to generate the iodine(III) or iodine(V) species in situ. In this Focus Review, recent developments of hypervalent iodine‐catalyzed reactions are described including some asymmetric variants. Catalytic reactions using recyclable hypervalent iodine catalysts are also covered.     

烯基碲化合物的合成及其在烯烃立体选择合成反应中的应用

综述了近年来烯碲化合物的合成及其在立体选择合成中的应用。参考文献49篇。     

Organocatalytic enantioselective synthesis of highly functionalized polysubstituted pyrrolidines

The organocatalytic conjugate addition of different aldehydes to beta-nitroacrolein dimethyl acetal, generating the corresponding highly functionalized nitroaldehydes in high yields and with high stereoselectivities, has been studied in detail. These transformations have been achieved by using both readily available starting materials in a 1:1 ratio as well as commercially available catalysts at a 10 mol % catalyst loading. Furthermore, a very short and efficient protocol has been devised for the preparation of highly enantioenriched pyrrolidines containing two or three contiguous stereocenters starting from the obtained Michael adducts. 3,4-Disubstituted pyrrolidines have been obtained in a single step by Zn-mediated chemoselective reduction of the nitro group followed by intramolecular reductive amination, and trisubstituted homoproline derivatives have been prepared by means of an olefination reaction and a cascade process involving chemoselective reduction of the nitro group followed by a fully diastereoselective intramolecular aza- Michael reaction.     

Stereoselective Organocatalytic Synthesis of Oxindoles with Adjacent Tetrasubstituted Stereocenters

Oxindoles with adjacent tetrasubstituted stereocenters were obtained in high yields and stereoselectivities by organocatalyzed conjugate addition reactions of monothiomalonates (MTMs) to isatin‐derived N‐Cbz ketimines. The method requires only a low catalyst loading (2 mol %) and proceeds under mild reaction conditions. Both enantiomers are accessible in good yields and excellent stereoselectivities by using either Takemoto’s catalyst or a cinchona alkaloid derivative. The synthetic methodology allowed establishment of a straightforward route to derivatives of the gastrin/cholecystokinin‐B receptor antagonist AG‐041R.     

Alternative Strategies with Iodine: Fast Access to Previously Inaccessible Iodine(III) Compounds

Non‐iodinated arenes can be easily and selectively converted into (diacetoxyiodo)arenes in a single step under mild conditions by using iodine triacetates as reagents. The oxidative step is decoupled from the synthesis of hypervalent iodine(III) reagents, which can now be prepared conveniently in a one‐pot synthesis for subsequent reactions without prior purification. The chemistry of iodine triacetates was also expanded to heteroatom ligand exchanges to form novel inorganic hypervalent iodine compounds.     

(Z)-α-Selanyl Alkenyl Grignard Reagents as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

(Z)-α-Selanyl alkenyl Grignard reagents 2 were prepared conveniently by treatment of (-bromovinylselenides 1 with magnesium filings in THF. Intermediates 2 were reacted with alkyl iodides in the presence of CuI or Pd(PPh3)4 to afford (Z)-1,2-disubstituted vinylselenides 3, which were cross-coupled with Grignard reagents in the presence of (PPh3)2NiCl2 to give trisubstituted alkenes 4 stereoselectively in good yields.     

Stereoselective Electrophilic Cyclization

Electrophilic cyclizations of unactivated alkenes play highly important roles in the synthesis of useful building blocks. This account describes our contributions to the rational design of monofunctionalized chiral Lewis base catalysts for enantioselective iodo‐ and protocyclizations. For the stereoselective promotion of electrophilic bromocyclizations, nucleophilic phosphite–urea cooperative catalysts have been designed.     

Organocatalytic,Enantioselective Dichlorination of Unfunctionalized Alkenes

The use of a new class of unsymmetrical cinchona‐alkaloid‐based, phthalazine‐bridged organocatalysts enabled the highly enantioselective dichlorination of unfunctionalized alkenes. In combination with the electrophilic chlorinating agent 1,3‐dichloro‐5,5‐dimethylhydantoin (DCDMH) and triethylsilyl chloride (TES‐Cl) as the source of nucleophilic chloride, 1‐aryl‐2‐alkyl alkenes were dichlorinated with enantioselectivities of up to 94:6 er. Initial mechanistic investigations suggest that no free chlorine is formed, and by replacement of the chloride by fluoride, enantioselective chlorofluorinations of alkenes are possible.     

Chiral Hypervalent Iodine Reagents: Synthesis and Reactivity

Chiral hypervalent iodine chemistry has been steadily increasing in importance in recent years. This review catalogues enantioselective transformations triggered by chiral hypervalent iodine(III/V) reagents, in stoichiometric or catalytic quantities, highlighting the different reactivities in terms of yield and enantioselectivity. Moreover, the synthesis of the most remarkable and successful catalysts has been illustrated in detail.