Palladium Catalyzed Annulation Of Dienes And Acetylenes

Author : Xiaoxia Zhang
Publisher :
ISBN 13 :
Total Pages : 404 pages
Book Rating : 4.:/5 (759 download)

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Download or read book Palladium and Iodine Approaches to 1,3-dienes, Heterocycles and Carbocycles written by Xiaoxia Zhang and published by . This book was released on 2005 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: A variety of highly-substituted 1,3-dienes and 1,3,5-trienes have been regio- and stereoselectively prepared by the palladium-catalyzed coupling of vinylic iodides, internal alkynes and organoboranes in moderate to good yields. The analogous three-component coupling of aryl halides, 1,3-dienes, and boronic acids provides a useful route to 3,6-disubstituted cyclohexenes. This method is a very concise and efficient way to synthesize these molecules, whose synthesis has previously required multi-step synthesis. A wide variety of substituted quinolines have been readily synthesized under mild reaction conditions by the 6-endo-dig electrophilic cyclization of N-(2-alkynyl)anilines by IC1, I2, Br2 and PhSeBr. The reaction affords 3-halogen-, selenium- and sulfur-containing, and 4-aryl-, alkyl- and vinylic quinolines in moderate to good yields. Quinolines bearing a hydrogen in the 3-position have been synthesized by the Hg(OTf)2-catalyzed ring closure of these same alkynylanilines. Substituted naphthalenes are readily prepared regioselectively under mild reaction conditions by the 6-endo-dig electrophilic cyclization of appropriate arene-containing propargylic alcohols with IC1, I2, Br2, NBS and PhSeBr. 3-Iodo-2-naphthols have also been prepared in excellent yields by the cyclization of analogous l-aryl-3-alkyn-2-ones. This methodology has been successfully extended to the synthesis of substituted carbazoles and dibenzothiophenes and readily accommodates various functional groups. The electrophile-induced intramolecular ipso-cyclization of 4-methoxyaryl alkynes provides an efficient approach to various 3-halogen-substituted spirotrienones under very mild reaction conditions. Substituted spiro[4.5]trienones, l-azaspiro[4.5]trienones, spiro[4.5]diones, l-oxaspiro[4.5]diones, and l-azaspiro[4.5]diones are all readily synthesized. IC1, I2 and Br2 are all effective electrophiles for this process. Arynes generated in situ from 2-(trimethylsilyl)aryl triflates and CsF undergo annulation by o-haloarenecarboxaldehydes in the presence of a Pd catalyst, providing a useful new method for the synthesis of fluoren-9-ones in good yields.