DTHDA reactions

Compounds with certain [3]heterodendralene structures including more complex substructures and substituents such as carbonyls, imines, and ylides are very popular, and hence many reports on their synthesis/generation, application and/or characterization, and so on, were found. However, only a few examples of their diene-transmissive hetero-Diels-Alder (DTHDA) reactions have been reported so far. For instance, although divinyl ketones ([3]-3-oxadendralenes, Scheme 2.1) are well recognized, for example, for their Nazarov cychzation [1] (see Chapter 3), only two reports are known on DTHDA reactions of p,p -diphenyl- and di-2-thienyl-substituted divinyl ketones vide infra) [8]. 

Some examples of other kinds of [3]- and [4]heterodendralene structures are actually known but are not so common (Scheme 2.1) [2-7]. The one or two of the heterocumulenic double bond can also be incorporated in [3]-2-azadendralene [6] or [4]diazadendralene [7]. Thus, many types of heterodendralene structures are identified, but their DTHDA reactions have not been reported so far. 

Scheme 2.2 illustrates the known types of [3]heterodendralenes that have been successfully used in DTHDA reactions to date. This chapter introduces the DTHDA reactions of both [3]heterodendralenes (heterotrienes) and of carbon-dendralenes with hetero dienophiles. 

The DTHDA reaction is a special case of the DTDA (diene-transmissive Diels-Alder) reaction in which one or more heteroatoms are contained within a cross-conjugated triene/polyene (heterodendralene) it-system, a dienophile it-system, or both. The DTHDA protocol is an efficient and attractive method for the stereoselective synthesis of a variety of heterocyclic systems. 

This example is a carbotriene DTHDA reaction with thioketone and carbon dienophiles and may be included in Section 2.3. 

In 1997, the first example of a DTHDA reaction of a cross-conjugated azatriene was reported by Saito s group (Scheme 2.8) [17]. Di(P-styryl)methanimines ([3]-3-azadendralenes) 41, which were prepared from corresponding ketones. 

DTHDA Reaction of Dioxatrienes as Masked Oxathiatrienes and Oxazatrienes... 

Scheme 2.21 DTHDA reaction with nitroso dienophiles and synthesis of diaminotetrol.

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