Markovnikov's rule

About: Markovnikov's rule is a research topic. Over the lifetime, 1284 publications have been published within this topic receiving 32703 citations. The topic is also known as: Markownikoff's rule.

Gold(I)-Catalyzed Activation of Alkynes for the Construction of Molecular Complexity

Abstract: 1.1. General Reactivity of Alkyne-Gold(I) Complexes For centuries, gold had been considered a precious, purely decorative inert metal. It was not until 1986 that Ito and Hayashi described the first application of gold(I) in homogeneous catalysis.1 More than one decade later, the first examples of gold(I) activation of alkynes were reported by Teles2 and Tanaka,3 revealing the potential of gold(I) in organic synthesis. Now, gold(I) complexes are the most effective catalysts for the electrophilic activation of alkynes under homogeneous conditions, and a broad range of versatile synthetic tools have been developed for the construction of carbon–carbon or carbon–heteroatom bonds. Gold(I) complexes selectively activate π-bonds of alkynes in complex molecular settings,4−10 which has been attributed to relativistic effects.11−13 In general, no other electrophilic late transition metal shows the breadth of synthetic applications of homogeneous gold(I) catalysts, although in occasions less Lewis acidic Pt(II) or Ag(I) complexes can be used as an alternative,9,10,14,15 particularly in the context of the activation of alkenes.16,17 Highly electrophilic Ga(III)18−22 and In(III)23,24 salts can also be used as catalysts, although often higher catalyst loadings are required. In general, the nucleophilic Markovnikov attack to η2-[AuL]+-activated alkynes 1 forms trans-alkenyl-gold complexes 2 as intermediates (Scheme 1).4,5a,9,10,12,25−29 This activation mode also occurs in gold-catalyzed cycloisomerizations of 1,n-enynes and in hydroarylation reactions, in which the alkene or the arene act as the nucleophile. Scheme 1 Anti-Nucleophilic Attack to η2-[AuL]+-Activated Alkynes

Metal-Initiated Amination of Alkenes and Alkynes.

Abstract: The catalytic production of organic molecules is one of the most important applications of organometallic chemistry. For this purpose the distinct reaction chemistry of organic ligands covalently bound to transition metals is exploited. Most organometallic chemistry has focused on the formation of carboncarbon or carbon-hydrogen bonds. The platinum group metals, in particular Pd and Rh, have been the most commonly used elements insfrequently commercializedscatalytic processes that include hydrogenation, hydroformylation and others. On the other hand, carbon-oxygen and carbon-nitrogen bonds are found in the majority of organic molecules and are of particular importance in physiologically active substances. However, catalytic organometallic reactions that lead to the formation of carbonheteroatom bonds are less common.1,2 The catalytic construction of carbon-nitrogen bonds in amines is particularly rare.3-10 Clearly, efficient catalytic routes to nitrogen based molecules are of great interest.11 Especially useful are catalytic hydroaminations of olefins and alkynes which avoid production of byproducts, like salts, generally observed in metal-catalyzed aminations of C-X derivatives (X ) e.g., halogen). However, known aminations of olefins often require stoichiometric use of transition metals and general methods for carrying out aminations catalytically are not yet available.12,13 Most of the present enantioselective syntheses of molecules bearing an amine functionality use classical stoichiometric reactions with chiral auxiliaries or utilize enantiomerically pure starting material.14-16 Hydroamination of alkenes and alkynes, which constitutes the formal addition of a N-H bond across a carbon-carbon multiple bond (Scheme 1), is a transformation of seemingly fundamental simplicity and would appear to offer the most attractive route to numerous classes of organo-nitrogen molecules such as alkylated amines, enamines or imines. Organic chemists have developed various synthetic approaches for the amination of olefins.17-19 Direct addition of nucleophiles H-NR2 to activated alkenes is of general importance for the synthesis of compounds with nitrogen atoms â to groups such as keto, ester, nitrile, sulfoxide, or nitro.13,20-23 These additions usually lead to the anti-Markovnikov products. On the other hand aliphatic olefins as well as most aromatic olefins are often aminated to give the Markovnikov product. One possibility to reverse the reactivity of aliphatic olefins is the use of electrophilic nitrogen radicals which have been used to obtain anti-Markovnikov products.24 In the past much work has been done on the activation of alkenes with stoichiometric amounts of metal.24 Reactions are mostly promoted by complexes of titanium,25 iron,26 zirconium,27 palladium28-31 and mercury.32,33 However, catalytic additions of amines H-NR2 to nonactivated double or triple bonds are still rare. Two basic approaches have been employed to catalytically effect aminations and involve either alkene/alkyne or amine activation routes (Scheme 2).34,140 Alkene activation is generally accomplished with late-transition-metal catalysts, which render coordinated olefins more susceptible to attack by † Dedicated to Dipl. Chem. Martin Eichberger (deceased 11/20/ 1997). 675 Chem. Rev. 1998, 98, 675−703

Catalytic Markovnikov and anti-Markovnikov functionalization of alkenes and alkynes: recent developments and trends.

Abstract: The regioselective functionalization of terminal alkenes and alkynes is of utmost importance for the synthesis of a wide variety of organic products. Based on the original observation by Vladimir Markovnikov-the pioneer of this field of research-in the 19th century, the possible regioisomeric products are classified as Markovnikov or anti-Markovnikov products. Contrary to traditional belief, it is nowadays possible to control the regiochemistry of various additions of nucleophiles to alkenes and alkynes by applying different transition-metal catalysts. Recent developments in this area of selective functionalization of alkenes and alkynes are reviewed.

Iron Catalysts for Selective Anti-Markovnikov Alkene Hydrosilylation Using Tertiary Silanes

Abstract: Alkene hydrosilylation, the addition of a silicon hydride (Si-H) across a carbon-carbon double bond, is one of the largest-scale industrial applications of homogeneous catalysis and is used in the commercial production of numerous consumer goods. For decades, precious metals, principally compounds of platinum and rhodium, have been used as catalysts for this reaction class. Despite their widespread application, limitations such as high and volatile catalyst costs and competing side reactions have persisted. Here, we report that well-characterized molecular iron coordination compounds promote the selective anti-Markovnikov addition of sterically hindered, tertiary silanes to alkenes under mild conditions. These Earth-abundant base-metal catalysts, coordinated by optimized bis(imino)pyridine ligands, show promise for industrial application.

Metal vinylidenes and allenylidenes in catalysis: applications in anti-Markovnikov additions to terminal alkynes and alkene metathesis.

Abstract: The involvement of a catalytic metal vinylidene species was proposed for the first time in 1986 to explain the regioselective formation of vinyl carbamates directly from terminal alkynes, carbon dioxide, and amines. Since this initial report, various metal vinylidenes and allenylidenes, which are key activation intermediates, have proved extremely useful for many alkyne transformations. They have contributed to the rational design of new catalytic reactions. This 20th anniversary is a suitable occasion to present the advancement of organometallic vinylidenes and allenylidenes in catalysis.