Katalytische Hydroaminierung von Alkenen und Alkinen

Nitrogen containing molecules are among the most important classes of chemical subbtances. They play an outstanding role as biologically active compounds as well as industrial chemicals. In the past these facts lead to the development of a large number of methods for the synthesis of amines, imines and enamines. While most of these well established methods employ ketones/altlehydes or nitro compounds as starting materials, the direct conversion of alkenes or alkynes into nitrogen containing compounds is not very common. This is surprising because the direct addition of amines or ammonia to alkynes and alkenes (hydroamination) represents the shortest and economically most interesting way for the synthesis of amines, imines and enamines. A general method for this transfomation would produce the desired nitrogen containing compounds in a single step without the production of waste. To solve this synthetic problem, several more or less successful attempts have been made in the past. In this review we describe established as well as new and promising methods for the catalytic hydroamination of alkenes and alkynes. The catalysts mentioned are alkali metals, alkali metal hydrides and amides, lanthanoid complexes, carly and late transition metal complexes as well as zeolithes. For each type of catalyst the reaction mechanism is described. Further, the scope and limitations of each procedure is discussed.     

Investigation into the allylation reactions of aldehydes promoted by the CeCl3.7H2O-NaI system as a Lewis acid

The Lewis acid promoted allylation of aldehydes has become an important carbon-carbon bond forming reaction in organic chemistry. In this context, we have developed an alternative over existing catalytic processes, wherein aldehydes are subject in acetonitrile to reaction of allylation with allyltributylstannane in the presence of 1.0 equiv of cerium(III) chloride heptahydrate (CeCl(3).7H(2)O), an inexpensive and mild Lewis acid. The allylation has been accelerated by using an inorganic iodide as a cocatalyst, and various iodide salts were examined. The procedure must use allylstannane reagent instead of allylsilane reagent, desirable for environmental reasons, but high chemoselectivity was observed, and this is opposite the results obtained with other classical Lewis acids such as TiCl(4) and Et(2)O.BF(3).     

Stereoselective entry to beta-linked C-disaccharides using a carbon-Ferrier reaction

[structure: see text] The synthesis of unsaturated beta-linked C-disaccharides by the Lewis acid-mediated reaction of 3-O-acetylated glycals with monosaccharide-derived alkenes is described. Deprotection and selective hydrogenation of an exocyclic carbon-carbon double, in the presence of an endocyclic double bond, for representative targets is also illustrated.     

Catalytic addition methods for the synthesis of functionalized diazoacetoacetates and application to the construction of highly substituted cyclobutanones

[reaction: see text] Methyl 3-(trialkylsilanyloxy)-2-diazo-3-butenoate undergoes Lewis acid-catalyzed Mukaiyama aldol addition with aromatic and aliphatic aldehydes in the presence of low catalytic amounts of Lewis acids in nearly quantitative yields. Scandium(III) triflate is the preferred catalyst and, notably, addition proceeds without decomposition of the diazo moiety. Diazoacetoacetate products from reactions with aromatic aldehydes undergo rhodium(II)-catalyzed ring closure to cyclobutanones with high diastereocontrol. Examples of complimentary Mannich-type addition reactions with imines are reported.     

Forming Stereogenic Centers in Acyclic Systems from Alkynes

The combined carbometalation/zinc homologation followed by reactions with α‐heterosubstituted aldehydes and imines proceed through a chair‐like transition structure with the substituent of the incoming aldehyde residue preferentially occupying a pseudo‐axial position to avoid the two gauche interactions. The heteroatom in the axial position produces a chelated intermediate (and not a Cornforth–Evans transition structure for α‐chloro aldehydes and imines) leading to a face differentiation in the allylation reaction. This method provides access to functionalized products in which three new carbon–carbon bonds and two to three stereogenic centers, including a quaternary one, were created in acyclic systems in a single‐pot operation from simple alkynes.     

Three characteristic reactions of alkynes with metal compounds in organic synthesis

Alkynes have two sets of mutually orthogonal π‐bonds that are different from the π‐bonds of alkenes. These π‐bonds are able to bond with transition metal compounds. Alkynes easily bond with the various kinds of compounds having a π‐bond such as carbon monoxide, alkenes, other alkynes and nitriles in the presence of the transition metal compounds. The most representative reaction of alkynes is called the Pauson–Khand reaction. The Pauson–Khand reactions include the cyclization of alkynes with alkenes and carbon monoxide in the presence of cobalt carbonyls. Similar Pauson–Khand reactions also proceed in the presence of other transition metal compounds. These reactions are the first type of characteristic reaction of alkynes. Other various kinds of cyclizations with alkynes also proceed in the presence of the transition metal compounds. These reactions are the second type of characteristic reaction of alkynes. These include cyclooligomerizations and cycloadditions. The cyclooligomerizations include mainly cyclotrimerizations and cyclotetramerizations, and the cycloadditions are [2 + 2], [2 + 2 + 1], [2 + 2 + 2], [3 + 2], [4 + 2], etc., type cycloadditions. Alkynes are fairly reactive because of the high s character of their σ‐bonds. Therefore, simple coupling reactions with alkynes also proceed besides the cyclizations. The coupling reactions are the third type of characteristic reactions of alkynes in the presence of, mainly, the transition metal compounds. These reactions include carbonylations, dioxycarbonylations, Sonogashira reactions, coupling reactions with aldehydes, ketones, alkynes, alkenes and allyl compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

X=Y-ZH Systems as potential 1,3-dipoles : Part 13. Prototropic generation of azomethine imines from hydrazones

Hydrazones of aldehydes and ketones undergo intermolecular cycloaddition to electronegative olefins via azomethine imines, formed by a formal 1,2-prototropic shift, in low to moderate yield on heating in xylene or ethanol. In some instances the reaction is diverted to give products derived (at least formally) from an ene reaction. Similar intramolecular cycloadditions occur with unactivated terminal alkenes and alkynes.     

Allylstannylation of carbon-carbon and carbon-oxygen unsaturated bonds via a radical chain process

In the presence of a radical initiator, allyltributylstannanes bearing an electron-withdrawing group at the beta-position smoothly reacted with electron-deficient terminal alkenes to give allylstannylated products in good yields. The stannyl group was introduced into the terminal carbon with high regioselectivity. The allylstannylation of homochiral 8-phenylmenthyl acrylate proceeded with moderate to good diastereoselectivity. Terminal and electron-deficient internal alkynes as well efficiently underwent the radical-initiated allylstannylation in an anti addition mode. The reaction of terminal alkynes showed the same regioselectivity as that of terminal alkenes. The present radical reaction was applicable to allylation of aromatic aldehydes and ketones.     

Stereoselective alkylation of alpha,beta-unsaturated imines via C-H bond activation

The stereoselective alkylation of alpha,beta-unsaturated imines via C-H activation followed by imine hydrolysis produces tri- and tetrasubstituted alpha,beta-unsaturated aldehydes. In the presence of a rhodium catalyst, alpha,beta-unsaturated N-benzyl imines derived from methacrolein, crotonaldehyde, and tiglic aldehyde undergo directed C-H activation at the beta-position and react with terminal alkenes and alkynes to form the tri- and tetrasubstituted alpha,beta-unsaturated imines with very high stereoselectivity. Hydrolysis to provide alpha,beta-unsaturated aldehydes can be performed under carefully controlled conditions that maintain the stereochemistry of the beta-alkylated imine products. Alternatively, for beta-alkylation products of the N-benzyl imine of methacrolein, hydrolysis can be performed under conditions that provide complete isomerization to the E isomer.     

Transition metal-catalyzed cyclocarbonylation in organic synthesis

Cyclocarbonylation reactions proceed mainly by the coupling reactions of carbonylation components with cyclization components having an unsaturated π-electron bond, in the presence of transition metal compounds. The representative reactions are cyclocarbonylation of alkynes by carbon monoxide such as Pauson–Khand reactions, hetero Pauson–Khand reactions, cyclocarbonylation of alkynyl alcohols, cyclocarbonylation of alkynyl amines, cyclocarbonylative alkyne–alkyne coupling reactions, and reductive cyclocarbonylation of alkynes. The other reactions are cyclocarbonylation of alkenes by carbon monoxide such as alkene–alkene coupling reactions, cyclocarbonylation with aldehydes, ketones, amines or imines, cyclocarbonylation of alkenyl alcohols. Carbonylation via cyclometalation, carbonylative ring expansion reactions, cyclocarbonylation by aldehydes, carboxylic acids or carboxylic acid esters are also cyclocarbonylation reactions. These reactions are conveniently used for organic syntheses, especially, for the syntheses of pharmaceutical intermediates.     

Multifunctional asymmetric catalysis

Two types of general and practical enantioselective catalysts, namely, bimetallic complexes and Lewis acid-Lewis base bifunctional catalysts were developed based on the concept of multifunctional catalysis. In the first part of this review, the first example of a catalytic enatioselective nitro-Mannich reaction as well as a direct catalytic enantioselective aldol reaction of 2-hydroxyacetophenone using bimetallic complexes is discussed. The new complex, composed of ytterbium, potassium, and BINOL in a ratio of 1:1:3, promoted the nitro-Mannich reaction of nitromethane with up to 91% ee. On the other hand, second generation ALB catalyzed an enantioselective and diastereoselective nitro-Mannich reaction of nitroalkanes in up to 83% ee with a diastereomeric ratio up to 7:1. Moreover, the reaction of aldehydes with 2-hydroxyacetophenone in the presence of LLB, KHMDS, and H2O selectively gave the corresponding anti-alpha,beta-dihydroxy ketones in up to 95% ee and, in the presence of the catalyst prepared from linked-BINOL and 2 eq of Et2Zn, selectively afforded the syn-alpha,beta-dihydroxy ketones in up to 86% ee. In the second part, the development of new catalysts displaying a Lewis acidity and a Lewis basicity is described. The Lewis acid of the catalyst activates aldehydes, imines, acyl quinoliniums, and ketones. At the same time, the Lewis base activates the nucleophile (TMSCN). Catalysts of this type produced a highly enantioselective cyanation of these electrophiles. Application of the catalytic enantioselective cyanosilylation of aldehydes to a total synthesis of epothilones is also described.     

Indium(III) chloride-catalyzed oxidative cleavage of carbon-carbon multiple bonds by tert-butyl hydroperoxide in water—a safer alternative to ozonolysis

An efficient and general method for the oxidative cleavage of alkenes and alkynes using tert-butyl hydroperoxide and indium(III) chloride as catalyst in water to give the corresponding carboxylic acids or ketones has been achieved. The reaction conditions are compatible with sensitive moieties such as peptide bonds, tert-butyl carboxylic esters and N-Boc-protected tryptophan. The catalyst could be recycled.     

STUDIES ON SULFINATODEHALOGENATION:THE REACTION OF POLYFLUOROALKYL IODIDES WITH 4-PENTENOIC ACID COMPOUNDS

The radical addition of polyfluoroalkyl iodides to carbon-carbon multiple bonds is one of the most important and general methods for synthesis of a variety of fluorine-containing organic compounds.^[1] Studies in our laboratory on stulfinatodehalogenation reaction showed that sodium dithionite was a excellent initiation reagent for the addition of polyfluoroalkyl iodides, bromides and halocarbons to alkenes, alkynes and conjugated dienes effectively under mild conditions.^[2]     

Application of organic selenides and tellurides in organic synthesis

This paper describes the progress on the synthesis of organic selenides and tellurides and their application in organic synthesis.Low valent selenium and telluronium compounds having high reducing selectivity can be used to form carbon-hydrogen bonds as special reducing reagents.Telluronium ylides can react with aldehydes and ketones by Wittig-type condensation to produce (E)-configuration alkenes stereoselectively.α-Phenylselanyl arsonium ylides were prepared by transyl-idation reaction of arsonium ylides with phenylselanyl halides which can undergo Wittig-type reactions with carbonyl compounds to give (Z)-α-selanyl-α,β-unsaturated compounds with high stereoselectiv-ity.Zirconium,tin,boron,halogen,metal or hetero-atom were introduced in organoselenium and telluronium compounds as new difunctional group reagents.Under transition metal catalysis,the corresponding cross coupling reactions provide new methods of formation of carbon-carbon double bonds,which were used in the stereoselective synthesis of     

Allylation of aldehydes and imines: promoted by reuseable polymer-supported sulfonamide of N-glycine

[reaction: see text] A allylation of aldehydes and imines (generated in situ from aldehydes and amines) with allyltributyltin promoted by recoverable and reusable the polymer-supported sulfonamide of N-glycine has been developed. Good to high yields were obtained in various cases. Most of the SnBu(3) residue can be recovered as Bu(3)SnCl. Highly stereoselective synthesis of N-Boc-(2S,3S)-3-hydroxy-2-phenylpiperidine 7 was achieved by using the P4a-mediated allylation of Boc-l-phenylglycinal as a key step.     

The catalytic hydroamination of alkynes

The direct addition of ammonia or primary and secondary amines to non-activated alkenes and alkynes is potentially the most efficient approach towards the synthesis of higher substituted nitrogen-containing products. It represents the most atom economic process for the formation of amines, enamines and imines, which are important bulk and fine chemicals or building blocks in organic synthesis. While the hydroamination of alkenes is still limited to more or less activated alkenes, great progress has been achieved in the case of alkynes over the last three years. To illustrate this progress, the review will mostly focus on recent developments in the field of intermolecular hydroamination of alkynes. However, if it is necessary for the discussion, older results and intramolecular reactions, which can be achieved more easily, will be mentioned as well.     

过渡金属催化的炔烃复分解反应

综述了过渡金属均相催化的炔烃复分解反应进展,主要分为两部分：一是炔烃复分解反应在炔烃合成中的应用,即从六、七十年代Mortreux催化剂的发现能均相催化炔烃的歧化反应,经过一系列的条件改造,合成了炔醚和二芳基乙炔等化合物,并提出了可能的两种机理：金属卡宾和金属卡拜机理;金属钼和钨的卡拜络合物相继合成,发现此类络合物能够催化官能化的二炔的复分解反应,合成一系列的大环化合物。二是炔烃复分解反应在合成高聚物中的应用,即钙和钨的卡拜络合物被用来催化ROMP和ADIMET反应合成高聚物,改良了的Mortreux催化剂也能催化高聚物的生成,这些高聚物在发光器件、有机"塑料"激光、液晶显示器上都有应用。     

3 d Transition Metal‐Catalyzed Hydrogenation of Nitriles and Alkynes

Selective hydrogenation of nitriles and alkynes is crucial considering the vast applications of reduced products in industries and in the synthesis of bioactive compounds. Particularly, the late 3d transition metal catalysts (manganese, iron, cobalt, nickel and copper) have shown promising activity for the hydrogenation of nitriles to primary amines, secondary amines and imines. Similarly, semihydrogenation of alkynes to E‐ and Z‐alkenes by 3d metals is adequately successful both via the transfer hydrogenation and by using molecular hydrogen. The emergence of 3d transition metals in the selective synthesis of industrially relevant amines, imines and alkenes makes this protocol more attractive. Herein, we provide a concise overview on the late 3d transition metal‐catalyzed hydrogenation of nitriles to amines and imines as well as semihydrogenation of alkynes to alkenes.     

Fluoride-catalyzed three-component coupling reaction of a silylphosphine, activated alkenes and aldehydes

A novel CsF-catalyzed three-component coupling reaction of a silylphosphine, activated alkenes and aldehydes is described. Multi-functional phosphines were obtained by forming both carbon-phosphorus and carbon-carbon bonds in good yields under mild conditions.     

A novel reduction reaction for the conversion of aldehydes, ketones and primary, secondary and tertiary alcohols into their corresponding alkanes

A novel one-pot reaction has been developed for the reduction of aldehydes, ketones and primary, secondary and tertiary alcohols into their corresponding alkyl function. This is also the first reported method which can efficiently reduce primary, secondary, or tertiary alcohols, without affecting carbon-carbon double bonds, into their corresponding alkyl function in high yields. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane.