The Diene-Transmissive Hetero-Diels-Alder Reaction

The Diene-Transmissive Hetero-Diels-Alder Reaction 

Cross Conjugation Dendralene, Radialene and Fidvene Chemistry, First Edition. 

3) Of course, there are many unknown [3]heterodendralene structures and higher ones. 

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. 

The merit and potential of the DTHDA methodology for heterocyclic synthesis can be widely extended by structural variations of both diene and dienophile the kind of heteroatoms, their number, and their positions in either the cross-conjugated triene/polyene ([3/ ] heterodendralene) or the dienophile framework, as well as the inter- or intramolecular cycloaddition mode, and control of regio-and stereoselectivities. 

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Such syntheses take advantage of transannular intramolecular hetero Diels-Alder reactions [426], another impressive example is the diene transmissive hetero Diels-Alder reaction of the thioketone 5-14. The diene 5-15 formed by this cycloaddition underwent a second Diels-Alder reaction with N-phenyl-maleimide to yield the fused polycycle 5-16 as single diastereomer (Fig. 5-5) [427]. 

I 2 The Diene-Transmissive Hetero-Diels-Alder Reaction... 

Furthermore, azo dienophiles have been employed in diene-transmissive hetero Diels-Alder reactions of cross-conjugated trienes which allow the straightforward construction of polycyclic compounds [297]. Theoretical interest has been directed to the hetero Diels-Alder reaction of diethyl azo di-carboxylate with 1,3-cyclohexadiene whose concerted course was demonstrated by means of a high pressure study [298]. 

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