1,16-dimethyl-dodecahedrane synthesis

Paquette [5] applied this chemistry very elegantly to the synthesis of 1,16-dimethyl-dodecahedrane (IS), as shown in Scheme 8.3. 

The diester 87 with the same tetracyclic skeleton as 83 had previously been prepared by Paquette et al. via a domino Diels-Alder reaction of 5,5 -bicyclo-pentadienyl 84 with dimethyl acetylenedicarboxylate (Scheme 20) [73]. The key precursor 84 was obtained by iodine-induced oxidative coupling of the copper cyclopentadienide derived from the sodium derivative. The diester 85 formed along with 86 was transformed into a bissilyl bisenol ether by reductive cleavage of the central bond in the succinate moiety with sodium in the presence of trimethylsilyl chloride. Subsequent hydrolysis of the bisenol ether - actually a bisketene acetal - gave the dienic tetraquinacenedicarboxylate 87. This compound served as the key intermediate in the first synthesis of dodecahedrane 88 [74]. 

The first step in a synthesis of dodecahedrane involves a Diels-Alder reaction between the cyclopentadiene derivative (1) and dimethyl acetylenedicarboxylate (2). Show how these two molecules react to form the dodecahedrane synthetic intermediate (3). 

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