The
past decade has witnessed the golden age of homogeneous gold-catalyzed
reactions, especially those that involve the transformation of highly
strained molecules into complex molecular architectures. Gold catalysts,
with unique electronic properties and catalytic abilities, have elevated
versatile reaction modes through π-interaction induced activation.
On the basis of increasing research interest in this topic, together
with the significant development of various ligands, including phosphine
ligands and azacyclic or noncyclic carbene ligands, the understanding
of the catalytic function of gold catalysts has become much deeper
and more comprehensive. Different reaction needs thus could be adapted
by a novel gold catalyst with a diversified ligand selection. Furthermore,
the whole evolution of the gold catalysis on synthetic methodologies
has realized and expanded its application into natural product synthesis
as well as the potentiality of drug discovery, which endows this ancient
metal with a magnificent renaissance. The reactivity of strained small
ring molecules with high tension has always been an important research
topic in organic chemistry. When the highly strained small ring is
linked with a π-electron rich moiety or contains a heteroatom,
the gold activation of the π-system or coordination with the
heteroatom can initiate a cascade reaction, usually followed by ring
opening or expansion. These processes can result in the rapid construction
of complex and distinct molecular structures, many of which feature
in biologically important molecules. In this review, we will mainly
summarize the advances on diverse reaction types and molecular constructions
accomplished by homogeneous gold catalysis using highly strained substrates,
including methylenecyclopropanes (MCPs), vinylidenecyclopropanes (VDCPs),
cyclopropenes as well as aziridine- and epoxide-containing molecules,
focusing on the last 10 years. For functionalized alkynyl cyclopropanes,
several early inspiring and elegant examples will be described in
this review for systematically understanding these transformations.
A gold-catalyzed cascade cyclization of O-tethered 1,7-enynes bearing a cyclopropane moiety has been reported in this communication, affording multi-substituted furans in moderate to good yields along with the further transformations.
A gold(I)-catalyzed ring expansion of alkynylcyclopropyl allyl ethers to produce tetrasubstituted methylenecyclobutanones in moderate to good yields has been disclosed in this paper. This reaction proceeded through an intramolecular [3,3]-sigmatropic rearrangement followed by [1,2]-allyl shift pathway in the presence of catalytic amount of water upon gold(I) catalysis. The intriguing reaction mechanism has been proposed on the basis of deuterium and 18 O-labeling experiments, Mass spectroscopic analysis, 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopic tracking and density functional theory (DFT) calculations. The further transformation of these methylenecyclobutanones into polycyclic skeleton has been realized by a practical three-step synthetic procedure. Several other transformations have been also indicated.Scheme 5. Further transformations of the synthesized tetrasubstituted methylenecyclobutanones.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.