Sanjuán Ana M, Rashid Muhammad A, García-García Patricia, Martínez-Cuezva Alberto, Fernández-Rodríguez Manuel A, Rodríguez Félix, Sanz Roberto
Área de Química Orgánica, Departamento de Química, Facultad de Ciencias, Universidad de Burgos, Pza. Misael Bañuelos s/n, 09001 Burgos (Spain) http://www2.ubu.es/ginves/cien_biotec/sintorg/uk/index.htm.
Chemistry. 2015 Feb 9;21(7):3042-52. doi: 10.1002/chem.201405789. Epub 2014 Dec 29.
Indenes and related polycyclic structures have been efficiently synthesized by gold(I)-catalyzed cycloisomerizations of appropriate ortho-(alkynyl)styrenes. Disubstitution at the terminal position of the olefin was demonstrated to be essential to obtain products originating from a formal 5-endo-dig cyclization. Interestingly, a complete switch in the selectivity of the cyclization of o-(alkynyl)-α-methylstyrenes from 6-endo to 5-endo was observed by adding an alcohol to the reaction media. This allowed the synthesis of interesting indenes bearing an all-carbon quaternary center at C1. Moreover, dihydrobenzo[a]fluorenes can be obtained from substrates bearing a secondary alkyl group at the β-position of the styrene moiety by a tandem cycloisomerization/1,2-hydride migration process. In addition, diverse polycyclic compounds were obtained by an intramolecular gold-catalyzed alkoxycyclization of o-(alkynyl)styrenes bearing a nucleophile in their structure. Finally, the use of a chiral gold complex allowed access to elusive chiral 1H-indenes in good enantioselectivities.
茚及其相关的多环结构已通过金（I）催化的适当邻（炔基）苯乙烯的环异构化反应高效合成。已证明烯烃末端位置的双取代对于获得源自形式上的5-内型-双环化的产物至关重要。有趣的是，通过向反应介质中添加醇，观察到邻（炔基）-α-甲基苯乙烯环化选择性从6-内型完全转变为5-内型。这使得能够合成在C1处带有全碳季中心的有趣茚。此外，通过串联环异构化/1,2-氢化物迁移过程，可以从在苯乙烯部分的β-位带有仲烷基的底物获得二氢苯并[a]芴。此外，通过对结构中带有亲核试剂的邻（炔基）苯乙烯进行分子内金催化的烷氧基环化反应，得到了多种多环化合物。最后，使用手性金配合物能够以良好的对映选择性获得难以捉摸的手性1H-茚。
