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Synthesis of substituted pyridines through a novel aza-annulation of 2-en-4-ynyl azides, derived from MBH-acetates of acetylenic aldehydes, is described. A variety of enynyl azides having aryl, heteroaryl, and alkyl groups on the alkyne functionality successfully participated in the Ag-mediated annulation reaction to provide the corresponding 3,6-disubstituted pyridines. I2-mediated cyclization was found to be controlled by the substituent on the alkyne functionality, which offered the 5-iodo-3,6-disubstituted pyridines from enynyl azides having an electron-rich substituent on the alkyne functionality.

A new entry for the synthesis of functionalized arylidene cyclopentenes under metal-free reaction conditions is disclosed via the base-promoted [4 + 1]-annulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with active methylene derivatives involving tandem allylic substitution followed by 5-exo-dig-carbocyclization.

One-pot synthesis of substituted pyrroles by a cascade reaction of azides with Morita-Baylis-Hillman acetates of acetylenic aldehydes is described and the reaction is efficiently mediated by triphenyl phosphine at room temperature. Sodium azide is successfully used to provide N-unsubstituted pyrroles, while alkyl azides afforded the corresponding N-alkylated pyrroles through a sequence of allylic substitution/azide reduction/cycloisomerization reactions. The obtained products have provided a new entry to indolizino indoles, pyrrolo isoquinolines and 8-oxo-5,6,7,8-tetrahydroindolizine.

A general strategy for the stereoselective total syntheses of cladospolides A, B, and C and iso-cladospolide B has been accomplished. The key steps provide easy access to the target molecules and include an alkyne-zipper reaction, a Sharpless asymmetric epoxidation/dihydroxylation, and a Yamaguchi macrolactonization. The feasibility of the alkyne-mediated approach to construct the required carbon framework as well as to create the diol functionality and the olefin geometry is successfully demonstrated. [ABSTRACT FROM AUTHOR]

A stereoselective formal synthesis of a 16-membered antibiotic macrolide (-)-A26771B is described starting from (R)-propylene oxide and (+)-diethyl tartrate. Key steps involved in this alkyne-assisted convergent approach are alkyne zipper reaction, Cadiot-Chodkiewicz coupling, and Yamaguchi macrolactonization. [ABSTRACT FROM AUTHOR]

Abstract: The Cu(I)-catalyzed cycloaddition of azido-alkynes (click reaction) of furanose sugar substrates provides a facile approach for the construction of macrocyclic molecules via an inter and/or intramolecular cycloaddition based on the functionality between alkyne and azide. [Copyright &y& Elsevier]

Abstract: Synthesis of a series of [1,2,3] triazolo [5,1-c] [1,4]benzoxazepine derivatives have been accomplished by the intramolecular Cu(I)-catalyzed cycloaddition of azido-alkynes derived from salicylaldehyde. The biological profile of these heterocyclic structural scaffolds toward anti-bacterial as well as anti-fungal activity has also been illustrated. [ABSTRACT FROM AUTHOR]