Multi-step transformations

Evidently Seyferth was the first to recognize the new opportunities of such variations in organosilicon chemistry.16 He generated dimethylsilylene in the presence of ketones and phosphines. According to authors hypothesis multi-step transformation takes place in the reaction (Scheme 2). 

The multi-functionality of metal oxides1,13 is one of the key aspects which allow realizing selectively on metal oxide catalysts complex multi-step transformations, such as w-butane or n-pentane selective oxidation.14,15 This multi-functionality of metal oxides is also the key aspect to implement a new sustainable industrial chemical production.16 The challenge to realize complex multi-step reactions over solid catalysts and ideally achieve 100% selectivity requires an understanding of the surface micro-kinetic and the relationship with the multi-functionality of the catalytic surface.17 However, the control of the catalyst multi-functionality requires the ability also to control their nano-architecture, e.g. the spatial arrangement of the active sites around the first centre of chemisorption of the incoming molecule.1... 

The next challenge will probably be to unlock the bottlenecks still existing in the use of whole cells as micro reactors for effective multi-step transformations and to develop technological tricks to allow the number of compounds usable by the technology to increase. 

The number of publications in the period of coverage of this chapter detailing the use of BusSnH, Me3SnH or Ph3SnH in synthesis, either in direct reduction chemistry, or in multi-step transformations, is truly remarkable. Indeed, it is not practical for all examples to be included in this account. It is our intention, therefore, to present a comprehensive description of the diversity of the chemistry in question through the use of numerous selected examples, while the entire list of references is included for completeness. 

Other routes to MMA start from ethylene, propylene or propyne and involve metal catalysis at some stage of multi-step transformations for example by the hydroformylation of ethylene to intermediate propionaldehyde, oxidation to propionic acid, followed by condensation with formaldehyde. The Pd-catalyzed carbonylation of propyne to MMA is a further method. However only the ethylene route has found some industrial application (see Chapter 4, Section 4.3.1). 

Develop catalysts capable of complex reactions by multi-step transformations at a single site ... 

Kirsch has reported the conversion of propargyl vinyl ethers to form pyrroles via a multi-step transformation involving the silver-catalyzed propargyl Claisen rearrangement to form the a-allenyl P-keto ester, condensation with a primary aryl amine. 

Dimethyl tartrate 6.260) is also an important chiral template. The first step was protection of the diol moiety to give acetonide 6.261. A multi-step transformation followed which gave 4-amino-2,3-dihydroxybutanoic acid, 6.262. This dihy-droxyamino acid was converted to anthopleurine (4-amino-2,3-dihydroxybutanoic acid, or 4-[N,N,N-trimethylammonium]-2,3-dihydroxybutanoic acid, 6.263), an alarm pheromone of the sea anemone Anthopleura elegantissima. ... 

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