New Ethynylpyridines
The alkyne functional group can be utilised in a wide range of reactions including hydrogenation, addition of halogens, hydrogen halides or H2O (followed by rearrangement to form the keto-tautomer), oxidation & hydroboration as well as the Favorski reaction which involves nucleophilic attack on a carbonyl carbon to generate propargyl alcohols.
Furthermore terminal alkynes can undergo several coupling reactions to give multifunctional alkynes, including Sonogoshira cross coupling with aryl halides using a palladium catalyst, Cu(I) and an amine base. Other coupling reactions include Cadiot-Chodkiewicz coupling of a terminal alkyne and alkynyl halide to give unsymmetrical bisacetylenes and Glaser coupling of terminal alkynes to give symmetrical bisacetylenes.
The main research interest in terminal alkynes in recent years has been in their use in the Huisgen cycloaddition of alkynes to azides to form 1,4 or 1,5-disubstituted-1,2,3-triazoles using either a Copper or ruthenium catalysed reaction respectively (Scheme 1 & 2). This reaction has generated much interest as it fulfils many of the requirements set out by Sharpless on the concept of ‘Click Chemistry’ and the reaction is regarded by Sharpless as ‘the cream of the crop’ of Click Chemistry1 and several 1,4-disubstituted-1,2,3-triazoles derivatives have shown potential as antiviral, antibacterial and antiproliferative agents.2
The availability of terminal heteroarylalkynes as starting materials was considered limited(4); however Apollo Scientific is now pleased to offer a range of pyridine substituted alkynes including those below:
(1) Kolb, H. C., Finn, M. G. and Sharpless, K. B. (2001), Click Chemistry: Diverse Chemical Function from a Few Good Reactions. Angew. Chem. Int. Ed., 40: 2004–2021
(2) Isabel Pérez-Castro, Olga Caamaño, Franco Fernández, Marcos D. García, Carmen López, and Erik de Clercq, ARKIVOC 2010 (iii) 152-168, http://www.arkat-usa.org/get-file/28898/ file last accessed 30/04/2012
(3) http://www.organic-chemistry.org/namedreactions/click-chemistry.shtm Click Chemistry Azide-Alkyne cycloaddition- accessed 30/04/12
(4) Alan R. Katritzky,* Boris V. Rogovoy, and Alexander Y. Mitrokhin, ARKIVOC 2002 (xiii) 17-27 http://www.arkat-usa.org/get-file/18782/ file last accessed 30/04/12
|
|
