Intramolecular routes to hydrindanes: the Diels-Alder and Michael aldol approach to 6-isopropyl-9-methylbicyclo[4.3.0]nonan-3-one

Abstract

Ausgehend vom Aldehyd (I) wird die im Titel genannte Verbindung (V) auf zwei Wegen hergestellt.

A Divergent Approach to the Marine Diterpenoids (+)‐Dictyoxetane and (+)‐Dolabellane V

“…[12] While this route proved highly efficient and enabled us to readily prepare multigram quantities (> 6g)o ft he key buildingblock 28,wealso wanted to determine whether an intramolecular Diels-Alder reaction (IMDA) of triene 27 could be av iable alternative to establish the trans-ring junction of 28. [32] However, exploration of the IMDA of 27 (see the Supporting Information for preparation of this compound) provedu nfruitful, and the [4+ +2] cycloaddition could not be induced under either thermalorh igh-pressure (14 kbar) conditions. [34] Ketone 28 was converted into the corresponding vinyl triflate, which was subjected to Pd-catalyzed reduction using al ow-boiling silane to afford olefin 29 in 75 %y ield.…”

Intramolecular rearrangements: Epimerization of bicyclic vinyl tertiary alcohols via a [2,3] sulfoxide sigmatropic rearrangement

“…A particularly powerful transformation for the intramolecular construction of cyclohexanones in these systems is the anionic oxy-Cope rearrangement. This [3,3] sigmatropic rearrangement proceeds under mild conditions (1) and occupies a central role in the approach to ophiobolin A being developed by Paquette et al (2), the route to taxusin under examination by Martin et al (3), and our own studies'directed toward the total syntheses of gascardic acid (4) and retigeranic acid (5). The general transformations 1 to 2 and 3 to 4 are representative of the type of multicyclic spiro-fused skeletons whose preparation may be envisaged using this chemistry.…”

Application of Pauson–Khand reaction in the total synthesis of terpenes

“…372 It was actually an attempt towards the total synthesis of the natural product, nitiol 558. 105,360,373 In 1995, Cordell and co-workers found out that the plant so-called Gentianella (G.) is a regular remedial plant that cultivates in the Andes area. Its extract contains several compounds with diverse structures showing various biological activities, extensively employed as folk medicine for the treatment of hepatitis, and obesity.…”

“…372 The important steps in this strategy are an asymmetric Pauson-Khand cycloaddition and a norrish type 1 fragmentation reaction. 105,360,373 The total synthesis started from diethyl methylmalonate 545 which upon alkylation with the appropriate tosylate in the presence of sodium hydride and catalytic amount of sodium iodide in DMF gave 2,2-disubstituted malonates 548 and 549. 377,378 The required enyne 551 and 550 were prepared via standard procedures involving, LAH reduction, TBSCl protection, oxidation, Corey-Fuchs or Nozaki reactions.…”