On the diastereofacial selectivity of Lewis acid-catalyzed carbon-carbon bond forming reactions of conjugated cyclic enones bearing electron-withdrawing substituents at the .gamma.-position

Diels−Alder Approach to Isoprostanes. Total Synthesis of iPF2α-V

“…A hydride reduction not unlike the one we were considering has been described. 35 However, as can be seen later, the hydride reduction did not proceed as anticipated. In summary, our plan was to use the asymmetric center in 14, which would correspond to carbon 6 in the final isoprostane, to control the stereocenters at 5 and 9 by the Diels-Alder reaction and the asymmetric center at 8 by a stereocontrolled reduction.…”

“…The reason for the unusual face selectivity was explained in terms of orbital interaction between the diene and dienophile. 35,41 We were intrigued by the contrasting results we obtained as compared to those in Scheme 10B and decided to have a closer look at the differences between the two reactions. We carried out the Diels-Alder reaction with dienophile 16b and butadiene 17c, under AlCl 3 conditions (Scheme 11, entry 1).…”

Chemistry of 4‐Hydroxy‐2‐cyclopentenone Derivatives

“…Rokach [90] and Danishefsky [91] have demonstrated the potential of Diels-Alder reactions for the transformation of the 4-hydroxy-2-cyclopentenone framework (Scheme 47, Eq. 1).…”

Diels-Alder reactions in aqueous media

“…It is of interest to note that the use of water as a solvent favors the formation of the anti-diastereomer 4.10, with the highest ratio (ds= 10/1) occurring with the parent 4-hydroxycyclopent-2-en-l-one (4.9a). Apparently, solvation of the hydroxyl group (and to some extent the esters in 4.9b and 4.9c) increases the effective steric bulk of this group and overrides the competing Cieplak stereoelectronic effect [50] which favors the syn-diastereomer 4.11 [51]. Of course, the use of water as a solvent need not have a beneficial effect on the diastereoselectivity of a Diels-Alder reaction whatsoever.…”