Agustín Cobas

Highly Selective Insertion of Arynes into a C(sp)−O(sp3) σ Bond

Arynes react with ethoxyacetylene to afford 2-ethoxyethynylaryl derivatives through a highly chemo- and regioselective formal insertion of the aryne into the C(sp)-O(sp(3)) bond of the alkyne. Computational studies suggest that the reaction does not proceed through a mechanism initiated by the nucleophilic addition of the oxygen atom to the aryne as previously proposed but by the addition of the triple bond of the alkyne to the aryne.

Aryne Insertion into I–I σ-Bonds

A new protocol for the efficient synthesis of o-diiodoarenes has been developed. This method allows the synthesis of substituted and polycyclic o-diiodoarenes, which are difficult to obtain by classical methods. This diiodination process involves the formal insertion of arynes into the I-I σ-bond.

Stereoselective Tandem Cascade Furan Cycloadditions

Oligofurans linked by a rigid tether undergo tandem cycloaddition reactions with high stereoselectivity. The reaction of bisfurans with dimethyl acetylenedicarboxylate (DMAD) involves tandem [4 + 2]/[4 + 2] cycloadditions in a pincer mode. The reaction of oligofurans with arynes involves stereoselective tandem [4 + 2]/[4 + 2] cycloaddition reactions in a domino mode. The corresponding aryne adducts have been transformed into extended perylene derivatives by deoxygenation and aromatization with HCl/EtOH.

Synthesis of Heterocyclic Antitumour Compounds Using Alkyne and Aryne Cycloadditions

The Diels-Alder reaction of α-pyrones with alkenes and alkynes is well known:1 some 40 years ago, Wittig and co-workers reported that the reaction of α-pyrone (1a) with benzyne (2) led to formation of naphthalene (4a).2 In fact, the initial adduct is the bicyclic intermediate 3a, which undergoes a retro-Diels-Alder reaction, losing CO2 to give the aromatic compound 4a. The intermediate 3a was not detected because its conversion to 4a is favoured on both enthalpic and entropic grounds. In the intervening years the synthetic potential of this transformation for construction of aromatic molecules from α-pyrones has hardly been exploited.3 Here we describe its application in the synthesis of some interesting compounds.