Intramolecular Diels—Alder reactions IMDA types

Another important application of the iminium catalysis concept has been the development of enantioselective Type I [15, 30] and Type II [15] intramolecular Diels-Alder reactions (IMDA). (For experimental details see Chapter 14.18.3). For these transformations, both catalysts 1 and 3 proved to be highly efficient, as demonstrated by both the short and effective preparation of the marine methabo-lite solanapyrone D via Type I IMDA (Scheme 3.4, top) and the development of an early example of an enantioselective, catalytic Type II IMDA reaction (Scheme 3.4, bottom) [35]. Importantly, cycloadducts incorporating ether and quaternary carbon functionalities could be efficiently produced. 

Two major classes of intramolecular Diels-Alder (IMDA) reactions may be identified based on the point of connection of the diene to the dienophile (Figure 1). Type I reactions involve trienes with the connecting chain attached to the diene terminus, while type 11 substrates have the dienophile tethered via one of the internal diene positions. 

The work of Ohno s group resulting in the first total synthesis of these structural types, benefited greatly from the concurrent investigations of the intramolecular Diels-Alder (IMDA) reaction [17]. Thus, there were (at least) three key principles on which they could rely [17, 18] ... 

Intramolecular Diels Alder (IMDA) reactions are extensively applied in the synthesis of polycyclic compounds. Most of these reactions require high temperatures to occur and hence these are catalyzed by Lewis acids to occur at ordinary temperatures. These reactions are classified into two types according to the connectivity of alkyl chain to the diene part at C-1 and C-2. Type-1 is very common. 

Intramolecular Diels-Alder (IMDA) reaction is a common type of Diels-Alder reaction. This is one of the powerful methods in the synthesis of polycyclic compounds and has been widely applied in the synthesis of complex natural products. 

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