Oxygenation with Other Reagents

Bis(trimethylsilyl)peroxide-triflic acid and sodium percarbonate-triflic acid are also efficient electrophilic oxygenating agents. Adamantane is transformed into 4-oxahomoadamantane in good yields obtained through C-C a-bond insertion [Eq. (6.57)]. 1 -Adamantanol, the C-H insertion product, is formed in a very small amount. Isomeric oxahomodiamantanes (C-C insertion) and bridgehead diamantanols (C-H insertion) are produced from diamantane.  

Tlie HOF-acetonitrile complex developed by Rozen et al. is an effective oxidizing agent capable of transforming tertiary C-H bonds under mild condi-tions. The reaction is interpreted to occur by the attack of the electrophilic 

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Oxygenation with Other Reagents Interestingly, when bicyclo[2.2.1] heptane (norbornane,75) reacts with nitronium tetrafl uoroboratc,bicyclo 2.2.1 ] heptan-2-one is formed in 70% yield, but no nitro derivative is isolated (Scheme 6.28). In addition, bicyclo[2.2.1]heptane-2-yl nitrite is observed as an intermediate. The initial steps of the transformation are either hydride abstraction to give 2-norbornyl cation 76 or insertion of N()2 into the secondary C-H bond (77). Both reaction pathways are possible. 

Black phosphorus may be either amorphous or crystalline. It exhibits quite low reactivity, both with oxygen and other reagents, compared to white or red phosphorus, and is stable in air. Because it has a puckered shape, the phosphorus remains tricoordinated in black phosphorus and crystallizes in sheets in a way similar to the behavior of graphite. Black phosphorus is generated from white phosphorus either by heating under pressure or in the presence of mercury. It is of relatively little value for the synthesis of organophosphorus compounds. 

Optimization of the ATP—hemoglobin reaction conditions produced a preparation having a markedly reduced oxygen affinity. Five fractions from a reaction mixture, when isolated, were found to have P q values ranging from 1.1 to 5.0 kPa (8 to 38 torr), most withUtfle cooperativity (118). These results are consistent with those found with other polyfunctional reagents that react on the surface of hemoglobin. 

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

A great advantage of catalyst 24b compared with other chiral Lewis acids is that it tolerates the presence of ester, amine, and thioether functionalities. Dienes substituted at the 1-position by alkyl, aryl, oxygen, nitrogen, or sulfur all participate effectively in the present asymmetric Diels-Alder reaction, giving adducts in over 90% ee. The reaction of l-acetoxy-3-methylbutadiene and acryloyloxazolidinone catalyzed by copper reagent 24b, affords the cycloadduct in 98% ee. The first total synthesis of ewt-J -tetrahydrocannabinol was achieved using the functionalized cycloadduct obtained [23, 33e] (Scheme 1.39). 

Ethylene reacts by addition to many inexpensive reagents such as water, chlorine, hydrogen chloride, and oxygen to produce valuable chemicals. It can be initiated by free radicals or by coordination catalysts to produce polyethylene, the largest-volume thermoplastic polymer. It can also be copolymerized with other olefins producing polymers with improved properties. Eor example, when ethylene is polymerized with propylene, a thermoplastic elastomer is obtained. Eigure 7-1 illustrates the most important chemicals based on ethylene. 

In the reaction cited above, the oxidizing agent is oxygen gas however, other reagents, for example, Mn02 and others, are normally used. The reaction of the oxidant Mn02 (this is not soluble in dilute acid) with ferrous iron is as follows ... 

For (hydroxyethyl)polystyrene to succeed as a versatile synthetic intermediate (57), techniques must be evolved to replace oxygen by other atoms which may be more suited to good function of final reagent. Such conversions must be completely quantitative, since unreacted, side-reacted or over-reacted functionalities cannot be removed from the solid product, and may ultimately interfere with its destined activity. 

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