Reactions Initiated by Oxidation or Reduction

During the past few years, increasing numbers of reports have been published on the subject of domino reactions initiated by oxidation or reduction processes. This was in stark contrast to the period before our first comprehensive review of this topic was published in 1993 [1], when the use of this type of transformation was indeed rare. The benefits of employing oxidation or reduction processes in domino sequences are clear, as they offer easy access to reactive functionalities such as nucleophiles (e. g., alcohols and amines) or electrophiles (e. g., aldehydes or ketones), with their ability to participate in further reactions. For that reason, apart from combinations with photochemically induced, transition metal-catalyzed and enzymatically induced processes, all other possible constellations have been embedded in the concept of domino synthesis. 

Domino Reactions in Organic Synthesis. Lutz F. Tietze, Gordon Brasche, and Kersten M. Gericke Copyright 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-29060-5 

Anion-triggered reactions, as discussed earlier in Chapter 2, embody transformations in most cases, in which a nucleophile acts as the attacking species towards an electrophile. Since oxidation and reduction procedures are well established for providing nucleophilic or electrophilic functionalities, they can be combined with anionic process. 

In the construction of C=N bond-containing compounds, such as nitrogen heterocycles, the aza-Wittig methodology has received increased attention as the method of choice [7]. Thus, an easy access to optically active (-)-vasicinone (7-15), a pyr-rolo[2,l-fc]quinazoline alkaloid which is used in indigenous medicine [8], was 

The Staudinger/aza-Withg procedure has recently also been used by Mellet and Fernandez for the synthesis of calystegine B2, B3, and B4 analogues, emphasizing the growing importance of this methodology [12]. 

---

Oxidation and reduction reactions play a vital role in the field of synthetic organic chemistry. Mild, selective, and economical catalytic oxidations as well as reduction reactions are recent developments in modern synthetic organic chemistry [1]. These transformations in combination with other reactions in a domino fashion give synthetically challenging organic products or intermediates in a very short and economical way [2]. After the first book by Tietze et al. [2a] in 2006 about domino reactions, where domino reactions initiated by oxidation or reduction reactions are reviewed as a separate chapter, enormous developments have taken place in the synthesis of a multitude of important organic compounds using oxidative or reductive domino reactions. 

Domino Reactions Initiated by Oxidation or Reduction Reaction... 

In this chapter, we presented the importance of oxidation and reduction reactions as part of a domino process in organic synthesis. Particularly, in the synthesis of complex organic molecules, this allows for short, simple, economical, as well as highly selective approaches in which several bonds are formed in one process. Domino reactions initiated by oxidation or reduction reactions have seen enormous growth in the last years. However, the protocols dealing with domino reactions having an oxidation or a reduction in the middle of a reaction sequence or as the terminating step are yet to be explored to their full potential. 

---