Two new polymorphs of zeolite beta, denoted as SU-78A and SU-78B, were synthesized by employing dicyclohexylammonium hydroxides as organic structuredirecting agents. The structure was solved by combining transmission electron microscopy and single-crystal X-ray diffraction. SU-78 is an intergrowth of SU-78A and SU-78B and contains interconnected 12-ring channels in three directions. The two polymorphs are built from the same building layer, similar to that for the zeolite beta family. The layer stacking in SU-78, however, is different from those in zeolite beta polymorph A, B, and C, showing new zeolite framework topologies. SU-78 is thermally stable up to 600 °C.
The first examples of one-pot highly chemo- and enantioselective dynamic kinetic asymmetric transformations (DYKATs) involving alpha,beta-unsaturated aldehydes and propargylated carbon acids are presented. These DYKATs, which proceed by a combination of catalytic iminium activation, enamine activation, and Pd(0)-catalyzed enyne cycloisomerization, give access to functionalized cyclopentenes with up to 99 % ee and can be used for the generation of all-carbon quaternary stereocenters.
Into the pot: A one‐pot highly chemo‐ and enantioselective catalytic domino oxa‐Michael/carbocyclization between α,β‐unsaturated aldehydes and propargylic alcohols is presented. This dynamic kinetic transformation requires a combination of transition‐metal and amine catalysis to afford functionalized dihydrofurans in good to high yields and up to 99.5:0.5 e.r.
The
reaction mechanism for the palladium and amine cocatalyzed
carbocyclization of aldehydes with alkynes has been investigated by
means of density functional theory calculations and experiments. The
Pd/amine cocatalyzed transformation is a carbocyclization of in situ
generated enaminynes where the C–C bond-forming step is most
likely promoted by a Pd(II) species. Notably, the latent Pd(0)/Pd(II)
catalytic redox cycle of this metal/organo cooperative catalytic reaction
can be merged with catalytic direct aerobic alcohol oxidation (Pd
oxidase catalysis).
The asymmetric synthesis of Maraviroc (UK-427,857), a chemochine receptor 5 (CCR-5) receptor antagonist, based on an expeditious organocatalytic enantioselective assembly of the chiral bamino aldehyde key fragment is presented. The reactions were performed on a gram-scale and allow for the rapid construction of new Maraviroc analogues.
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.