A new and efficient metal-free cascade cyclization of 1,6-enynes with aldehydes is developed for the synthesis of tricyclic fluorene derivatives. The reaction involves a radical process and one C(sp2)–C(sp2) and two C(sp2)–C(sp3) bonds are formed simultaneously in one pot by using PivOH and TBHP.
An iodine-promoted one-pot radical cyclization reaction of 1,6-enynes with sulfonyl hydrazides to provide five-membered and hexatomic ring sulfonylated products under the same conditions is established. This reaction proceeded smoothly in water and gave the corresponding products by using I-2/TBHP instead of expensive and toxic catalysts with C-S and C-I bond formed in one step. This method also allowed easy access to significant functional sulfones for potential applications in medicinal and organic chemistry.
Gold(I)-Catalyzed Intramolecular [4+2] Cycloadditions of Arylalkynes or 1,3-Enynes with Alkenes: Scope and Mechanism
作者:Cristina Nieto-Oberhuber、Patricia Pérez-Galán、Elena Herrero-Gómez、Thorsten Lauterbach、Cristina Rodríguez、Salomé López、Christophe Bour、Antonio Rosellón、Diego J. Cárdenas、Antonio M. Echavarren
DOI:10.1021/ja075794x
日期:2008.1.1
The cyclizations of enynes substituted at the alkyne gives products of formal [4+2] cyclization with Au(I) catalysts. 1,8-Dien-3-ynes cyclize by a 5-exo-dig pathway to form hydrindanes. 1,6-Enynes with an aryl ring at the alkyne give 2,3,9,9a-tetrahydro-1H-cyclopenta[b]naphthalenes by a 5-exo-dig cyclization followed by a Friedel-Crafts-type ring expansion. A 6-endo-dig cyclization is also observed