Redox-economy

For an overview of redox economy in organic synthesis, see Baran PS, Hoffmann RW, Bums NZ (2009) Angew Chem Int Ed 48 2854... 

At this stage in the project, we decided to use a model system to try and learn more about the potential of future steps in the synthetic route. As such, the orthoester of acid 35 was formed (36 Scheme 5). Ozonolysis and addition of a vinyl Grignard reagent were not successful however, the failure of this process was possibly due to cleavage and decomposition of the orthoester. To further simplify the process, the acid was protected by reduction to the alcohol (38) and formation of the sUyl ether 39. While this was not ideal for an eventual synthetic route for reasons of step/atom/redox economy, a silyl ether would be more stable to future conditions and help determine... 

Burns, N. Z., Baran, P. S. Hoffmann, R. W. (2009). Redox economy in organic synthesis. Angewandte Chemie International Edition, 48, 2854-2867. 

Since then, many synthetic chemists have been confronted with strychnine, which is a classic among the classics of total synthesis. Overall, 18 total syntheses of strychnine have been reported so far [58a-r], the shortest one in only 7 linear steps from tryptamine by Vanderwal [58r], to be compared with the earliest total synthesis of Woodward in 29 linear steps from phenylhydrazine [53a], The efficiency of these works can be evaluated by looking at the overall yields, from 0.00014% [58a] to nearly 10% yield [58e]. For sure, these improvements not only took benefits from Corey s retrosyn-thetic Logic of Chemical Synthesis but also from those famous chemists s creativity and from new achievanents in synthetic and catalytic methodologies. Indeed, new methodological concepts have arisen by the last 20 years, such as those of ideal synthesis [59], atom economy, step economy, redox economy, and sustainable approaches [60]. 

Nickel and copper are two metals that are important to the Ontario economy, particnlarly in the Sndhnry area. Nickel and copper ores usually contain the metals as snlfides, snch as NiS and Cn2S. Do the extractions of these pure elemental metals from their ores involve redox reactions Explain your reasoning. 

O Nickel and copper are both very important to the Ontario economy. Before they can be refined by electrolysis, they must be extracted from their ores. Both metals can be extracted from a sulfide ore, NiS or CU2S. The sulfide is roasted to form an oxide, and then the oxide is reduced to the metal. Research the extraction processes for both nickel and copper, and write balanced equations for the redox reactions involved. One product of each extraction process is sulfur dioxide. Research the environmental effects of this compound. Describe any steps taken to decrease these effects. 

Aqueous systems have been studied by a very large number of investigators. Economy, safety, convenience and quality of product have combined to make this the method of choice for commercial production of copolymers. The industrial importance of such end products as elastomers and acrylic fibers has been a special incentive to related fundamental studies. Furthermore, the relatively high solubility of acrylonitrile monomer in water coupled with insolubility of the polymer make it a convenient test monomer for studies of initiation by redox systems (6, 25, 102). Large numbers of homogeneous chemical initiators and some heterogeneous initiators have been studied as well as initiation by photochemical means, by ultrasonics and by ionizing radiation. It will not be possible here to review the enormous world literature. Several publications (/, 92, 117) refer in some detail to the older papers, and we shall restrict our comments to recent interpretations that have received support from several quarters. 

An important consideration for auto manufacturers today is fuel economy and pollution reduction. Fuel cells represent one option to achieve these goals. Like a battery, a fuel cell produces electricity from a redox reaction. Unlike a battery, a fuel cell can generate electric current indefinitely because it oxidizes a continuous stream of fuel from an outside source. 

Application of this catalyst system to propargyl alcohols provides a, 3-unsaturated aldehydes (Equation 1.17) and ketones (Equation 1.18) [18]. The ease of accessibility of the substrates by simple addition of terminal alkynes to aldehydes followed by this redox isomerization constitutes a highly chemoselective and atom economic strategy to these unsaturated carbonyl compounds. The chemoselectivity problems of the direct aldol condensation and the poor atom economy of olefination methods make this new strategy the most efficient and reliable approach to these units. 

This is a reaction with high atom economy and without the use of organometallic reagents, additives, or redox systems. Such an acetoxypalladation-initiated carbon-heteroatom multiple bond insertion-protonolysis system may extend the scope of transition metal-catalysed reactions pertaining to the insertion of carbon-heteroatom multiple bonds into metal-carbon bonds, and provide a new methodology in organic synthesis. The generality of the present catalytic system is shown in Table 10.2.[3]... 

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