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Gold(I)‐Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho ‐(Alkynyl)styrenes
Author(s) -
Sanjuán Ana M.,
Rashid Muhammad A.,
GarcíaGarcía Patricia,
MartínezCuezva Alberto,
FernándezRodríguez Manuel A.,
Rodríguez Félix,
Sanz Roberto
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405789
Subject(s) - cycloisomerization , chemistry , moiety , nucleophile , styrene , catalysis , olefin fiber , medicinal chemistry , alkyl , stereochemistry , combinatorial chemistry , organic chemistry , polymer , copolymer
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 1 H ‐indenes in good enantioselectivities.