Acetylene diethers: Dineopentyloxyethyne

Dineopentyloxyethyne has been synthesized fromtrans-2,3-dichloro-1,4-dioxane according to a general procedure already described. In contrast with alkyl neopentyloxyacetylenes, RC=COCH₂Bu^t, which only polymerize when are strongly heated (150°), dineopentyloxyethyne is a kinetically unstable acetylene diether that polymerizes readily at room temperature. However, the compound has been trapped with Co₂(CO)₈ to give either the corresponding hexacarbonyl complex, m.p. 74–75°, or the cyclic trimer, m.p. 205–206°, depending upon the experimental conditions.     

Improved Synthesis of Tricyclo (5.2.1.04,10) Decane-2,5,8-Trione by a Pauson-Khand Intramolecular Bis-Annulation

The title compound 1 has been synthesized from diol 3a, either directly or after protection of the two hydroxy groups as benzyl ethers, by an intramolecular Pauson-Khand bis-annulation, followed by catalytic hydrogenation and oxidation in overall yields ranging from 15% (free diol) to 35% (dibenzyl ethers).     

Studies on the pauson-khand reaction. Exclusive formation of angularly fused triquinanes from bicyclo[3.3.0]oct-2-ene and propargyl derivatives

Reaction of bicyclo[3.3.0]oct-2-ene with different hexacarbonyl dicobalt complexes of propargyl derivatives leads, under a great variety of experimental conditions, to the exclusive formation of angularly fused triquinanes, the corresponding reduced products being formed if the reaction is run at high temperature. The intermediacy of a π-allyl complex is suggested in order to account for these results, as well as for the presence of minor amounts of Diels-Alder adducts in the reaction mixture.     

Direct entry to the all-cis tricyclo[5.2.1.O4,10]decane (perhydrotriquinacene) skeleton by a cobalt mediated intramolecular cyclization

The perhydrotriquinacene skeleton has been synthesized by a Pauson-Khand bis-annulation process.     

Synthetic applications of di-tert-butoxyethyne,II: New syntheses of squaric,semisquaric and croconic acids

New synthetic entries to: a) the semisquaric acid skeleton of the natural mycotoxin “moniliformin”; b) the squaric acid system, and c) the croconic acid system, via (η-tetra-tert-butoxycyclopentadienone)(η-cyclopentadienyl)cobalt, starting from di-tertbutoxyethyne are reported.     

Stereoselectivity in Intramolecular Cobalt-Mediated Bis-Annulations Leading to Triquinacene Derivatives

In order to account for the high stereoselectivity observed in the intramolecular cobalt-mediated bis-annulation of 2a,b a ^SN¹ epimerization of the C(5) assymmetric center must be postulated.     

Intramolecular cyclization of bis-α-diazoketones: A new synthesis of γ-tropolone

Catalytic decomposition of bis-α-diazoketones (3, n = 3), in inert solvents, under high dilution affords cycloalk-2-ene-1,4-diones (4, n = 3). The method has been applied to a new synthesis of γ-tropolone 5 in five steps from glutaconic acid 6.