A novel strategy for the asymmetric construction of functionalized 4-aryl-3,4-dihydrocoumarins and 4-aryl-3,4-dihydroquinolin-2-ones via an intramolecular vinylogous Rauhut-Currier reaction of para-quinone methides (p-QMs) under the bifunctional catalysis of chiral amine-phosphine is described. This intramolecular mode for the catalytic enantioselective 1,6-conjugate addition of p-QMs has been explored for the first time, delivering two types of synthetically important heterocycles in high yields and enantioselectivites.
A novel base-mediated tandem spirocyclopropanation/rearrangement reaction of vinyl p-quinone methides (p-VQMs) with sulfonium salts is described. The unprecedented reactivity of p-VQMs was explored for the first time in the spiroannulation cascade, providing a stereoselective approach to the construction of synthetically interesting, densely functionalized spirocyclopentenyl p-dienones.
With the aid of a
class of newly discovered Trost-type bisphosphine
ligands bearing a chiral cycloalkane framework, the Pd-catalyzed decarboxylative
dearomative asymmetric allylic alkylation (AAA) of benzofurans was
achieved with high efficiency [0.2–1.0 mol% Pd2(dba)3/L], good generality, and high enantioselectivity
(>30 examples, 82–99% yield and 90–96% ee). Moreover,
a diversity-oriented synthesis (DOS) of previously unreachable flavaglines
is disclosed. It features a reliable and scalable sequence of the
freshly developed Tsuji–Trost–Stoltz AAA, a Wacker–Grubbs–Stoltz
oxidation, an intra-benzoin condensation, and a conjugate
addition, which allows the efficient construction of the challenging
and compact cyclopenta[b]benzofuran scaffold with
contiguous stereocenters. This strategy offers a new avenue for developing
flavagline-based drugs.
We
achieved a concise total synthesis of salimabromide by using
a novel intramolecular radical cyclization to simultaneously construct
the unique benzo-fused [4.3.1] carbon skeleton and the vicinal quaternary
stereocenters. Other notable transformations include a tandem Michael/Mukaiyama
aldol reaction to introduce most of the molecule’s structural
elements, along with hidden information for late-stage transformations,
an intriguing tandem oxidative cyclization of a diene to form the
bridged butyrolactone and enone moieties spontaneously, and a highly
enantioselective hydrogenation of a cycloheptenone derivative (97%
ee) that paved the way for the asymmetric synthesis of salimabromide.
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.