Alkyl terminal oxidant

Out first example is 2-hydroxy-2-methyl-3-octanone. 3-Octanone can be purchased, but it would be difficult to differentiate the two activated methylene groups in alkylation and oxidation reactions. Usual syntheses of acyloins are based upon addition of terminal alkynes to ketones (disconnection 1 see p. 52). For syntheses of unsymmetrical 1,2-difunctional compounds it is often advisable to look also for reactive starting materials, which do already contain the right substitution pattern. In the present case it turns out that 3-hydroxy-3-methyl-2-butanone is an inexpensive commercial product. This molecule dictates disconnection 3. Another practical synthesis starts with acetone cyanohydrin and pentylmagnesium bromide (disconnection 2). Many 1,2-difunctional compounds are accessible via oxidation of C—C multiple bonds. In this case the target molecule may be obtained by simple permanganate oxidation of 2-methyl-2-octene, which may be synthesized by Wittig reaction (disconnection 1). 

There are several available terminal oxidants for the transition metal-catalyzed epoxidation of olefins (Table 6.1). Typical oxidants compatible with most metal-based epoxidation systems are various alkyl hydroperoxides, hypochlorite, or iodo-sylbenzene. A problem associated with these oxidants is their low active oxygen content (Table 6.1), while there are further drawbacks with these oxidants from the point of view of the nature of the waste produced. Thus, from an environmental and economical perspective, molecular oxygen should be the preferred oxidant, because of its high active oxygen content and since no waste (or only water) is formed as a byproduct. One of the major limitations of the use of molecular oxygen as terminal oxidant for the formation of epoxides, however, is the poor product selectivity obtained in these processes [6]. Aerobic oxidations are often difficult to control and can sometimes result in combustion or in substrate overoxidation. In... 

The AE reaction catalyzed by titanium tartrate 1 and with alkyl hydroperoxide as terminal oxidant has been applied to a large variety of primary allylic alcohols containing all eight basic substitution patterns. A few examples are presented in Table 6.2. 

Homogeneous Systems Using Molybdenum and Tungsten Catalysts and Alkyl Hydroperoxides or Hydrogen Peroxide as the Terminal Oxidant... 

On the basis of published data for enthalpies of formation, sublimation, and vaporization, the dissociation enthalpies of terminal N—O bonds, DH°(N—O), in various organic compounds including nitrile oxides, were calculated and critically evaluated (18). The derived DH°(N—O) values can be used to estimate enthalpies of formation of other molecules, in particular nitrile oxides. N—O Bond energy in alkyl nitrile oxides was evaluated using known and new data concerning kinetics of recyclization of dimethylfurazan and dimethylfuroxan (19). 

This procedure, which is based entirely on commercially available reagents, is very easy to reproduce. Table 6.12 shows different aryl- and alkyl-substituted enones that can be epoxidised with high asymmetric induction with the in situ formed (/ )-BINOL-zinc-catalyst in diethyl ether, with cumene hydroperoxide as the terminal oxidant. 

In work by Hanrath and Korgel, H-terminated Ge nanowires were exposed to hexene in a supercritical fluid reactor at 220 °C, and the resulting hexyl-terminated nanowires appear resistant to oxidation in either air or water. The image reveals an abrupt interface for the alkyl-terminated Ge nanowire (Figure 5.12(b)) compared to the nanowires removed from the reactor without termination (Figure 5.12(a)) [103]. 

Biodegradation of LAS involves co-oxidation of the alkyl terminal C-atom to an alcohol which is further oxidized via an aldehyde to a carboxylic acid, usually followed by (i-oxi-dation until no further acetyl-CoA can be cleaved off the former surfactant molecule. Since intermediates of the subsequent reactions hardly can be isolated, co-oxidation appears likely the rate-limiting step in LAS biodegradation. 

Acetals result from oxidative coupling of alcohols with electron-poor terminal olefins followed by a second, redox-neutral addition of alcohol [11-13]. Acrylonitrile (41) is converted to 3,3-dimethoxypropionitrile (42), an intermediate in the industrial synthesis of thiamin (vitamin Bl), by use of an alkyl nitrite oxidant [57]. A stereoselective acetalization was performed with methacrylates 43 to yield 44 with variable de [58]. Rare examples of intermolecular acetalization with nonactivated olefins are observed with chelating allyl and homoallyl amines and thioethers (45, give acetals 46) [46]. As opposed to intermolecular acetalizations, the intramolecular variety do not require activated olefins, but a suitable spatial relationship of hydroxy groups and the alkene[13]. Thus, Wacker oxidation of enediol 47 gave bicyclic acetal 48 as a precursor of a fluorinated analogue of the pheromone fron-talin[59]. 

The formation of structures on silicon with SAM especially on a nanometer scale has been demonstrated with different physical and/or chemical methods. An often used method is local anodic oxidation (LAO), where the monolayer is eliminated and the first layers of silicon beneath are oxidized leading to silicon oxide structures on the silicon surface. This method can be used to create structures on alkyl-terminated silicon within the range of nanometers [8]. The formed silicon oxide, which contains negative charges due to the oxidation... 

Generally, arene(alkoxy)carbene chromium complexes react with aryl-, alkyl-, terminal or internal alkynes in ethers or acetonitrile to yield 4-alkoxy-l-naphthols, with the more hindered substituent ortho to the hydroxyl group . Upon treatment with alkynes, aryl(dialkylamino)carbene chromium complexes do not yield aminonaphthols, but they form indene derivatives . Vinyl(dialkylamino)carbene complexes, however, react with alkynes to yield aminophenols as the main products The solvent is one of the many factors that affects this type of reaction, for which the most important is the polarity and/or coordinating ability of the solvent. The Dotz benzannulation reaction yields either arene chromium tricarbonyl complexes or the decomplexed phenols, depending on the work-up conditions. Oxidative work-up yields either decomplexed phenols or the corresponding quinones. 

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