The mechanistic puzzle of transition-metal-catalyzed skeletal rearrangements of enynes.
Three pathways actually compete in metal-catalyzed cyclizations of enynes in which the metal selectively activates the alkyne: an endocyclic process and two exo-cyclizations, one proceeding by anti attack of the alkene and a second one resulting in a syn addition. Although cyclobutenes may be formed in transition-metal-catalyzed cyclization of some enynes, particularly, 1,7-enynes, these compounds are not necessarily the intermediates in the skeletal rearrangement. Cyclobutenes are formed by ring expansion of syn-cyclopropyl metal-carbenes formed in the syn pathway.
Nieto-Oberhuber
Cristina
C
Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona, Spain.
López
Salomé
S
Jiménez-Núñez
Eloísa
E
Echavarren
Antonio M
AM
D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D008968:Molecular Conformation; D013237:Stereoisomerism; D028561:Transition Elements / Q000737:chemistry*
D000475:Alkenes; D000480:Alkynes; D028561:Transition Elements