Some Applications in Organic Synthesis

Weight% of water = Water/(Water + Silica -h TPPTS + Rh precursor) 

The accelerating influence was explained by the establishment of hydrogen bonds between water and the ester group in the corresponding Rh- acyl complex. [38] This prevents the formation of a stable chelate, which could be responsible for the progress of the catalytic reaction. The content of water, the surface area. 

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Addition of Active Methylenes In the previous decade Cinellu et al. studied certain 1,3-dicarbonyl gold complexes and some applications in organic synthesis were subsequently proposed [78]. Intermolecular addition of activated methylene compounds to alkenes was developed by using AuCl3/AgOTf [79]. 

Calcium has received some application in organic synthesis similar to that of magnesium alkyl and aryl compounds, CaRa, have been prepared, and it seems likely that many of the magnesium syntheses, already mentioned, could be accomplished by the use of calcium. 

This chapter will emphasize the synthesis, stabilization, spectroscopic and structural aspects, reactivity and synthetic use of these compounds. For completeness, a summary of the subject previously reviewed3-10 will be included together with recent examples from the literature. The material will be divided into three sections preparations, spectroscopic and structural studies (with some characteristic spectroscopic and structural data) and reactivity (with some applications in organic synthesis). Each part will be organized into sections dealing with a particular element in the order germanium, tin and then lead. 

Despite their thermal instability, the distannyl peroxides have found some application in organic synthesis as a source of nucleophilic peroxide. Secondary alkyl peroxides are difficult to prepare by nucleophilic substitution by alkaline hydrogen peroxide because the products are decomposed under the alkaline conditions, but they can be obtained in fair yield by treating alkyl triflates with bis(tributyltin) peroxide.128-135... 

This chapter deals with the organotin compounds of the Main Group metals that have usually been studied more thoroughly, and of those transition metals that have attracted more attention because the compounds find some application in organic synthesis. A more comprehensive account is given in Glockling s review.5... 

V. Conte, F. Di Furia, Catalytic oxidations with hydrogen peroxide as oxidant. Peroxometal complexes derived from hydrogen peroxide. Some applications in organic synthesis. Catalysis by Metal Complexes 9 (1992) 223-252. 

This contribution encompasses the main concepts supporting the origin of the reactivity in water, along with some applications in organic synthesis with the exception of transition-metal-catalyzed reactions, which are fully described in Section 2.2. 

Stereoselective Reduction of 3-Ketosulfoxides Some Applications in Organic Synthesis... 

As we saw in Chapter 14, lanthanides have some applications in organic synthesis. 

Dihydro-1-vinylnaphthalene (67) as well as 3,4-dihydro-2-vinylnaphtha-lene (68) are more reactive than the corresponding aromatic dienes. Therefore they may also undergo cycloaddition reactions with low reactive dienophiles, thus showing a wider range of applications in organic synthesis. The cycloadditions of dienes 67 and 68 and of the 6-methoxy-2,4-dihydro-1-vinylnaphthalene 69 have been used extensively in the synthesis of steroids, heterocyclic compounds and polycyclic aromatic compounds. Some of the reactions of dienes 67-69 are summarized in Schemes 2.24, 2.25 and 2.26. In order to synthesize indeno[c]phenanthrenones, the cycloaddition of diene 67 with 3-bromoindan-l-one, which is a precursor of inden-l-one, was studied. Bromoindanone was prepared by treating commercially available indanone with NBS [64]. 

Nickel-catalyzed hydroalumination has found some specific applications in organic synthesis (see below). 

Inter- and intramolecular (cyclometallation) reactions of this type have been ob-.served, for instance, with titanium [408,505,683-685], hafnium [411], tantalum [426,686,687], tungsten [418,542], and ruthenium complexes [688], Not only carbene complexes but also imido complexes L M=NR of, e.g., zirconium [689,690], vanadium [691], tantalum [692], or tungsten [693] undergo C-H insertion with unactivated alkanes and arenes. Some illustrative examples are sketched in Figure 3.37. No applications in organic synthesis have yet been found for these mechanistically interesting processes. 

This class of ion-radicals is characterized by the localization of an unpaired electron at the atom bearing a free (valence) electron pair. Although their applicability in organic synthesis remains an open question, the preparative methods and electron structure of carbene ion-radicals attract some attention of the researchers. Probably, it is an initial step to a new chapter in organic ion-radical chemistry. 

The metal-catalyzed decomposition of diazo compounds has broad applications in organic synthesis [1-8]. Transient metal carbenoids provide important reactive intermediates that are capable of a wide variety of useful transformations, in which the catalyst dramatically influences the product distribution [5]. Indeed, the whole field of diazo compound decomposition was revolutionized in the early 1970s with the discovery that dirhodium tetracarboxylates 1 are effective catalysts for this process [9]. Many of the reactions that were previously low-yielding using conventional copper catalysts were found to proceed with unparalleled efficiency using this particular rhodium catalysis. The field has progressed extensively and there are some excellent reviews describing the breadth of this chemistry [5, 7, 10-17]. 

The C-H activation of allylic and benzylic C-H bonds has considerable application in organic synthesis. Studies by Muller [131] and Davies [130] on reactions with cyclohexene revealed that Rh2(S-DOSP)4 in a hydrocarbon solvent is the optimum system for high asymmetric induction (Tab. 14.13). Although this particular example gives a mixture of the C-H activation product 179 and cyclopropane 180, similar reactions with ethyl diazoacetate gave virtually no C-H activation product. Some of the other classic chiral dirhodium catalysts 181 and 182 were also effective in this chemistry, but the en-antioselectivity with these catalysts (45% ee and 55% ee) [131] was considerably lower than with Rh2(S-DOSP)4 (93% ee) [130]. 

Abstract Bismuth(III) salts are currently considered efficient and ecofriendly reagents and catalysts for the development of new applications in organic synthesis. The preparation of bismuth(III) triflate and its analogues is reviewed as well as some of their applications to the synthesis of bulk chemicals via electrophilic addition and cyclization reactions. The use of bismuth(III) salts in the development of new chemical processes involving steroids and terpenes as substrates is also discussed. 

The benzyl radicals generated by efficient deprotonation or electrofugal group loss from the benzylic position of arene radical cations (Eq.4) have found interesting applications in organic synthesis [25]. Some of the examples pertaining to this class are exemplified in Sect. 2.5. A recent publication of Santamaria et al. [26] illustrates the use of PET generated benzylic radicals (via deprotonation step from arene radical cations) for selective and mild photo-oxidation of... 

Halo-, carbo-, and nitro-mercurations of alkenes (and alkynes) have been previously described. However, these reactions are not as general and have not found as many applications in organic synthesis as the ones described in the previous two sections. Consequently, they will not be discussed any further in this review and the interested readers are directed to previous reviews and some recent references. ... 

Ionic liquids have numerous applications in organic synthesis. Some of the important reactions have proved that ionic liquids are truly versatile catalysts. Reaction media include, esterification reaction [67, 68], aldol condensation [69, 70], hydrogenation [71], Friedel-Crafts reactions [72,73], oxidation [74-76], Henry reaction, cross-coupling reactions [77,78], and some enzyme reactions [79, 80]. 

Acetic anhydride [108-24-7], (CH3C0)20, is a mobile, colorless liquid that has an acrid odor and is a more piercing lacrimator than acetic acid [64-19-7]. It is the largest commercially produced carboxylic acid anhydride U.S. production capacity is over 900,000 t yeady. Its chief industrial application is for acetylation reactions it is also used in many other applications in organic synthesis, and it has some utility as a solvent in chemical analysis. 

Solid-Liquid PTC. Despite the many applications in organic synthesis of SLPTC, only a few studies have reported the mechanism and kinetics of the SLPTC cycle. In carrying out a substitution reaction in a solid-hquid system, the quat (Q X ) approaches the solid surface and undergoes ion exchange with the solid nucleophilic salt at or near the solid interface (or in some cases within the solid) to form Y, followed by reaction oiQ Y with the organic substrate RX. 

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