Triquinanes: a "one-pot" IMDA-tandem metathesis cascade strategy: ring-closing metathesis (RCM) dominates norbornene ROM!

A general route to linear triquinanes including a formal synthesis of (+/-)-Delta(9(12))-capnellene is described. This cascade strategy combines an intramolecular Diels-Alder reaction tandem metathesis protocol to generate the linear cis-anti-cis-tricyclo[6.3.

Vinigrol: a compact, diene-transmissive Diels-Alder strategy to the tricyclic core.

A short (six steps from 17), versatile route to the tricyclic core of Vinigrol is described. A Lewis acid catalyzed and self-assembled Diels-Alder (LACASA-DA) reaction from the homoallylic cross-conjugated trienol 15 with N-methylmaleimide afforded the monoadduct 17 with diastereo-, regio-, and chemoselective control. Oxidation and installation of an acetylene (Ohira's reagent) followed by further manipulations afforded trienone 24.

Double diels-alder strategies to soluble 2,9- and 2,9,6,13-tetraethynylpentacenes, photolytic [4 + 4] cycloadditions, and pentacene crystal packing.

Four new classes of organic solvent soluble ethynylpentacene derivatives (2,9-, 2,10-, 2,6,9,13-, 2,6,10,13-) have been prepared by complementary, versatile, double Diels-Alder strategies. Functional groups on the A, C, and E rings can be manipulated to increase the solubility, modulate the electronics, and alter the solid-state packing. Cycloaddition reactions with diene 2 and 1,4,5,8-anthradiquinone (3) or ortho-quinodimethane 19 with 1-butyl-3-methylimidazolim iodide (18) as the iodide source (a significant improvement over NaI) and benzoquinone (20) followed by in situ aromatization afforded the quinones 4, 5, 21, and 22, respectively.

Diene-transmissive cycloadditions: control of monocycloaddition by self-assembly on a Lewis acid template.

The sequential control of diene-transmissive Diels-Alder reactions to expand their versatility for natural product synthesis and the preparation of diversity oriented libraries is described. Self-assembly of the components (trienol 5 and methyl acrylate) via a Lewis acid template proceeds with regio-, diastereo-, and enantioselective [(S)-BINOL added] control to the monoadduct. In contrast, no cycloaddition reaction occurred at 22 degrees C in the absence of catalyst.

A general carbometalation, three component coupling strategy for the synthesis of alpha,beta-unsaturated gamma-sultines including thio-rofecoxib, a selective COX-2 inhibitor.

Magnesium mediated carbometalation (Grignard addition) to appropriate propargyl alcohols to synthesize a cross-section of variably substituted alpha,beta-unsaturated gamma-sultines is described. Thio-rofecoxib, a selective COX-2 inhibitor (12), is synthesized by this method and its IC(50), microM COX-1 and COX-2 inhibition, and whole blood stability values reported.

Aryl annulation of cyclic ketones via a magnesium carbometalation-6-pi- electrocyclization protocol.

A new strategy for the aryl annulation of cyclic ketones is described. Palladium(0) coupling of a propargyl alcohol with the enol triflate of a ketone and addition of vinylmagnesium chloride generates a triene as a magnesium chelate that may be quenched with an electrophile. In some cases, the triene cyclizes under the reaction conditions.

(Z)-tamoxifen and tetrasubstituted alkenes and dienes via a regio- and stereospecific three-component magnesium carbometalation palladium(0) cross-coupling strategy.

[reaction: see text] The synthesis of various tetrasubstituted alkenes and dienes in a regio- and stereocontrolled manner is described. This three-component coupling strategy involves the addition of Grignard reagents to propargyl alcohols followed by palladium(0)-mediated cross-coupling with aryl or vinyl halides. This protocol has been applied to the synthesis of (Z)-Tamoxifen and related mimics.

Molecular folding of C60 acetylenic cyclophanes: pi-stacking of superimposed aromatic rings.

[structure: see text] The syntheses of two distinct families of phenylyne helical cyclophanes with potential for organic materials are described. The meta-bonded atropisomers afford interesting bowtie-like and butterfly-like conformers from a palladium(0), copper-mediated coupling sequence. Molecular modeling revealed the contrasting stereochemistry in these systems from differential molecular folding pathways during cyclization.

A novel strained undecadiyne cyclophane with interesting dienophilic character.

[reaction: see text] Copper-mediated oxidative coupling of 3 afforded the strained product 4 from intramolecular cyclization rather than the triply bridged cyclophane 5 from dimerization. X-ray analysis of the bromo derivative 15 confirmed the distorted nature of the butadiyne bridge (bond angles 164.1 degrees and 153.