Tandem-domino reactions

Tandem (Domino) reactions, in which two or more bond-forming processes result from a single step, are useful for rapid synthesis of complex molecules.138 Functionalized allylsilanes and the related silicon compounds have frequently been used for tandem reactions, because of their ease of synthesis and moderate, controllable reactivity. Recently, much attention has been paid to the use of multifunctional allylsilanes bearing another reactive group on silicon. 

Complementary Aspects of Natural Product Syntheses by Tandem-Domino Reactions and MCR Chemistry... 

Tandem domino reactions [10] are processes in which every reaction step brings about the structural change required for the following reaction step. The reaction proceeds without modification of the conditions or addition of supplementary... 

In contrast with tandem domino reactions. Tandem consecutive reactions [11] require modification of the reaction conditions or addition of supplementary reagents after completion of the first reaction step to facilitate propagation of... 

Tandem domino and tandem consecutive reactions do not necessarily involve more than one reactant and can be unimolecular, as is exemplified by such processes as polyolefin cyclization [13]. Tandem sequential reactions cannot be unimolecular processes and involve two reactants at least. Both, tandem sequential and higher-order tandem domino reactions are of foremost interest in this text, because they enable the concept of multicomponent reactions (MCRs) to be introduced [4, 7-9]. Depending on the reaction conditions, MCRs can be regarded as a subclass of either tandem sequential (Scheme 17.1a) or higher order tandem domino reactions (Scheme 17.1b). In the former, formation of intermediate AB is followed by addition of a third component C to the reaction mixture to enable formation of reaction product ABC. In the latter, components A, B, and C are simply... 

A more recent application of the Knoevenagel reaction is its use in domino reactions. The term domino reaction is used for two or more subsequent transformations, where the next reaction step is based on the functionality generated in the preceding step. Such reactions are also called tandem reactions or cascade reactions. 

Tietze L. F. Domino-Reactions the Tandem-Knoevenagel-Hetero-Diels-Alder Reaction and Its Application in Natural Product Synthesis J. Heterocycl. Chem. 1990 27 47-69... 

For clarification, individual transformations of independent functionalities in one molecule - also forming several bonds under the same reaction conditions -are not classified as domino reactions. The enantioselective total synthesis of (-)-chlorothricolide 0-4, as performed by Roush and coworkers [8], is a good example of tandem and domino processes (Scheme 0.1). I n the reaction of the acyclic substrate 0-1 in the presence of the chiral dienophile 0-2, intra- and intermolecular Diels-Alder reactions take place to give 0-3 as the main product. Unfortunately, the two reaction sites are independent from each other and the transformation cannot therefore be classified as a domino process. Nonetheless, it is a beautiful tandem reaction that allows the establishment of seven asymmetric centers in a single operation. 

Keyword Carbocycles a Cascade Reactions a Cycloadditions a Combinatorial Chemistry a Domino Reactions a Enantioselective Transformations a Ene Reactions a Eieterocydes a Natural products a Preservation of Resources and Environment a Sigmatropic Rearrangements a Tandem Reactions a Transition Metal-Catalyzed Transformations... 

In conclusion, the applicability of the transition metal catalyzed hydroformylation of easily accessible functionalized or non-functionalized unsaturated compounds is expanded by its implementation in reaction sequences, tandem reactions or domino reactions. The hydroformylation can be combined with simple functional group transformations, such as reduction or isomerization, or with C,0-, C,N- and, most importantly, C,C-bond forming reactions. It can be expected that more interesting examples and applications will be presented in the future. 

Hydroformylation reactions have been shown to be amenable to use in tandem or domino reaction sequences. In one elegant example, alkene 36 was subjected to rho-dium(I)-catalyzed hydroformylation, and the resulting aldehyde underwent smooth intramolecular allylboration (Scheme 5.14) [19]. This produced a new terminal alkene which underwent a second hydroformylation to provide, after workup,lactols 37 in 80% yield and with excellent diastereoselectivity. 

Wittig yhdes have been shown to be compatible with hydroformylation conditions, and may thus be used in a domino reaction sequence such as from 16a to 38 (Scheme 5.15) [20]. When an a-unsubstituted ylide is employed, the resulting alkene undergoes in-situ rhodium-catalyzed hydrogenation in a triple tandem reaction to convert 10 a to 39. Several other examples were reported establishing the generality of this domino reaction sequence. 

Tietze LF (1990) Domino-reactions - the tandem-Knoevenagel-hetero-Diels-Alder reaction and its application in natural product synthesis. J Heterocycl Chem 27 47-69... 

Irreversible self-assembly involves the formation of a product through a series of irreversible (usually covalent) bond-forming steps under kinetic control. There is no margin for self-correction and any mistakes are fatal to the formation of the final assembly. This class of reaction is not of significant interest in supramolecular chemistry but is topical in organic synthesis as tandem or domino reactions.2... 

Domino reaction Tandem ozonolysis-aldol sequence 225... 

Patterns of cyclic carbopalladation. As discussed above, the fundamentally stoichiometric and living nature of carbopalladation imposes various difficulties to be overcome. Carbopalladation can, in principle, be either a single-stage process or double- or multiple-stage processes. Double-and multiple-stage carbopalladation reactions have often been called either domino or cascade carbopalladation reactions. In some cases, two-stage carbopalladation reactions have also been called tandem carbopalladation reactions. None of these three words is a chemical term, and choice between them is a matter of taste. In this chapter, the term cascade will be used for both double- and multiple-stage carbopalladation processes. 

Jang et al. reported a highly diastereoselective tandem radical reaction to prepare -polysubstituted homoallylic alcohols (Scheme 64) [175]. This new process relies on the initial addition of benzoyl radicals onto an olefin. The intermediate radicals such as 201 underwent a stereoselective vinylation (two elementary steps) to form the desired Bz-protected homoallylic alcohols in good yields. The stereochemical outcome of the reaction is strongly dependent on polar factors such as solvent polarity of Lewis acid additives. More sophisticated domino processes including cyclizations can be devised, as is the case for the formation of 203. 

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