Remote Asymmetric Induction about a Crowded Aromatic Core

Abstract

Described are among the first highly diastereoselective, one-pot organometallic addition and hydride reduction reactions (>95% de) involving three symmetry-equivalent carbonyl centers, each that bears a 1,5-relationship to its nearest neighbor. Three-fold methyllithium addition to 2,4,6-trimethoxybenzene-1,3,5-tricarbaldehyde gives the anti,syn triol exclusively (by 1H NMR); addition of HMPA to the reaction or replacement of the substrate's methoxy groups with ethyl groups affords a statistical 3:1 (anti,syn:syn,syn) diastereomeric product ratio. Analogous asymmetric induction is found upon hydride reduction (using LiAlH4 or NaBH4) of the complementary triketone, 2,4,6-trimethoxybenzene-1,3,5-triethanone. Chelation and steric (gearing) effects about the crowded aromatic core contribute to the observed stereoselectivity.

Assessable Consequences of Through‐Bond Donor–Acceptor Interactions in β‐Aminoketones

“…Using methodology outlined previously for the exploration of diastereoselective additions to crowded phloroglucinol derivatives,16 tripentyl AAT 9 is prepared starting from versatile trialdehyde 19 17. Three‐fold addition of n ‐butyllithium produces triol 20 as a mixture of anti , syn and syn , syn isomers (Scheme ); the mixture is then subjected to trimethylsilyl hydride reduction as described for similar compounds by Biali and co‐workers to give 21 18.…”

Totalsynthese von Myrtucommulon A

“…Das als Erstes eluierende 11 a erwies sich als Racemat, das als Zweites eluierende 11 b als meso ‐Form. Demnach fällt 1 bei unserer Synthese als Mischung dreier Stereoisomere an, eines Enantiomerenpaars und einer meso ‐Verbindung 18. Schließlich konnten wir für synthetisches 1 aus Aceton Kristalle erhalten, die für eine Röntgenstrukturanalyse19 geeignet waren (Abbildung 2).…”

Reactions of Aldehydes and Ketones and their Derivatives

“…236 Two diastereoselective reactions have been performed: (i) the trial can be trimethylated to give triol (81) with methyllithium in THF, and (ii) the triketone can be reduced (to the same product), in both cases with >95% de (anti, syn). Chelation and steric (gearing) effects about the crowded aromatic core are discussed to explain the observed diastereoselectivity.…”