Diels-Alder reaction dodecahedrane

One step in the synthesis of dodecahedrane (Section 4.11) invoived reaction of the tetraene A with dimethyiacetyiene dicarboxylate (B) to afford two compounds having moiecuiar formuia C16H16O4. This reaction has been caiied a domino Diels-Alder reaction. Identify the two products formed. 

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). 

Stereoselectivity. See Asymmetric induction Axial/equatorial-, Cis/trans-, Enantio-, Endo/exo- or Erythro/threo-Selectivity Inversion Retention definition (e.e.), 107 footnote Steric hindrance, overcoming of in acylations, 145 in aldol type reactions, 55-56 in corrin synthesis, 261-262 in Diels-Alder cyclizations, 86 in Michael type additions, 90 in oiefinations Barton olefination, 34-35 McMurry olefination, 41 Peterson olefination, 33 in syntheses of ce-hydrdoxy ketones, 52 Steric strain, due to bridges (Bredt s rule) effect on enolization, 276, 277, 296, 299 effect on f3-lactam stability, 311-315 —, due to crowding, release of in chlorophyll synthesis, 258-259 in metc-cyclophane rearrangement, 38, 338 in dodecahedrane synthesis, 336-337 in prismane synthesis, 330 in tetrahedrane synthesis, 330 —, due to small angles, release of, 79-80, 330-333, 337... 

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