Pagodane

The strained undecacyclic pagodane framework was obtained in a series of 14 one-pot operations with an overall yield up to 24% from commercial isodrin. The key steps are (i) a benzene-benzene [6 -I- 6]photocycloaddition, and (ii) a domino Diels-Alder reaction. 

A domino reaction,in this case consisting of an inter- and an intramolecular Diels-Alder reaction, is a key step in the synthesis of the hydrocarbon pago-dane 30, reported by Prinzbach et al When the bis-diQnQ 27 is treated with maleic anhydride 4, an initial intermolecular reaction leads to the intermediate product 28, which cannot be isolated, but rather reacts intramolecularly to give the pagodane precursor 29 ... 

The combination of two successive [4+2] cycloadditions has already been described by Diels and Alder [la] for the reaction of dimethyl acetylenedicarboxylate with an excess of furan. A beautiful, more modern, example is the synthesis of pagodane (4-5) by Prinzbach [2], in which an intermolecular Diels-Alder reaction of 4-1 and 4-2 to give 4-3 is followed by an intramolecular cycloaddition. The obtained 4-4 is then transformed into 4-5 (Scheme 4.1). 

SCHEME 8. Competition between pincer and domino Diels-Alder reactions in the synthesis of pagodane precursurs92... 

The isodrine framework was used for synthesis of pagodane in which one of the key steps is Mackenzie s transannular dyotropic hydrogen transfer101. Also, a very intriguing ... 

Strategies based on known, highly elaborated, but nevertheless readily accesible, starting materials with a "complexity index" as near as possible to the "complexity index" of the target molecule. This strategy has also been applied to non-natural compounds as, for instance, in the synthesis of triquinacene by Woodward [37] and in the syntheses of dodecahedrane by Paquette (Domino Diels-Alder adduct) [38] and Prinzbach ("pagodane") and their associates [39]. 

Pagodane dications 247 Dehydroadamantanediyl dication 249 2,10-para[3,5]octahedranedimethyl dication 250 Bis(Tropylium) dications 251... 

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