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No base is necessary: Excellent yields are produced on addition of organoboronic acids to alkynes under mild reaction conditions when palladium compounds are used as catalysts (see scheme). Unlike the Suzuki-type cross-coupling reaction, the current reaction occurs in an acidic medium.

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTHighly Efficient Arylation of Malonates with Diaryliodonium SaltsChang Ho Oh, Joo Sung Kim, and Hyung Hoon JungView Author Information Department of Chemistry, Hanyang University, Haengdang-17 Sungdong-Gu, Seoul 133-791, Korea Cite this: J. Org. Chem. 1999, 64, 4, 1338–1340Publication Date (Web):February 4, 1999Publication History Received3 June 1998Published online4 February 1999Published inissue 1 February 1999https://pubs.acs.org/doi/10.1021/jo981065bh

o-(1,6-Enynyl)benzaldehydes underwent a novel mode of cycloaddition using Rh(I)-precatalyst, via[3+2] cycloaddition of presumed dipolar carbonyl ylide intermediate generated by Rh-catalyst and the utility of this mechanistically intriguing enyne cyclization can be found in a number of polycyclic natural product skeletons.

Access granted: The platinum-catalyzed cyclization of enynals 1, which contain an additional alkene bond in their side chain, through a [3+2] cycloaddition to give tetracyclic platinum–carbene complexes A was followed by CH insertion at the δ position to afford highly complex products 2. These polycyclic compounds and related products of the title transformation are extremely difficult to access by other means.

We have developed an efficient method for the synthesis of 2,3-disubstituted indoles from alkyne iminoethers 1 that employs a domino process involving Ag-catalyzed condensation followed by a tandem Ag-induced cycloisomerization and 1,3-alkenyl shift to Ag-activated carbon. This methodology can be useful in regioselectively constructing 3-alkylated indoles, which are part of the structures of biologically active compounds and important alkaloids.

A palladium [2 + 2] cycloaddition of 1,6- and 1,7-allenyne carboxylates and microwave-mediated [2 + 2] cycloaddition of various 1,n-allenynes were developed and, particularly, the microwave irradiated [2 + 2] cycloaddition of allenynes can provide a simple, general and eco-friendly synthetic method to fused bicyclo[m,2,0]alkadienes.

Good fusion: We describe the reactivity of Pt–carbene B, derived from enynals 1 via A, with Pt catalysts to afford fused cyclopropanes 2, which are obtained by insertion into the CH bond of the β position. Acid-catalyzed rearrangement of the cyclopropanes 2 smoothly occurred to form spiranes 3 (see scheme).

The Pd-catalyzed reaction of unsymmetrical alkynes with organoboronic acids gave a mixture of products and, whose ratios were controlled by the electronic as well as steric effects of the substrates.

Various 2-[6-en-1-ynyl]benzaldehydes and their analogues were successfully cyclized via Huisgen-type [3+2] cycloaddition to the tetracyclic platinum-carbene complex, which would subsequently undergo hydration to afford the tricyclic products in good yields with excellent stereoselectivities. This hydrative cyclization was also applied to the faveline synthesis.

2-Alkynyl-1-cycloalkenecarbaldehydes, in the presence of gold catalysts, undergo aurative cyclization via the 5-exo-dig mode to form Au-carbene intermediates which react with a double bond to form the corresponding cyclopropanes.