A belt-shaped [8]cycloparaphenylene
(CPP) and an enantioenriched
Möbius-shaped [10]CPP have been synthesized by high-yielding
rhodium-catalyzed intramolecular cyclotrimerizations of a cyclic dodecayne
and a pentadecayne, respectively. This Möbius-shaped [10]CPP
possesses stable chirality and isolated with high enantiomeric purity.
It is evident from the reaction Gibbs energy calculation that the
above irreversible cyclotrimerizations are highly exothermic; therefore
establishing that the intramolecular alkyne cyclotrimerization is
a powerful route to strained cyclic molecular strips.
Three become one: The cationic rhodium(I) complex [Rh(cod)2]BF4 catalyzes the [2+2+1] cross‐cyclotrimerization of silylacetylenes and two alkynyl esters, leading to substituted silylfulvenes (see scheme; cod=1,5‐cyclooctadiene). The reductive complexation of the silylfulvene product with RhCl3 in EtOH furnished the corresponding dinuclear electron‐deficient cyclopentadienyl rhodium(III) complex.
We have established that a cationic rhodium(I)/(R,R)-QuinoxP* complex catalyzes the highly enantioselective direct intermolecular hydroacylation of alpha-substituted acrylamides with unfunctionalized aliphatic aldehydes to yield the corresponding gamma-ketoamides in high yields with excellent ee values.
A dinuclear (electron‐deficient η5‐cyclopentadienyl)rhodium(III) complex was synthesized on a preparative scale via the rhodium‐catalyzed cross [2+2+1] cyclotrimerization of silylacetylenes and two alkynyl esters, leading to substituted silylfulvenes, followed by reductive complexation with rhodium(III) chloride in ethanol. The thus obtained dinuclear (electron‐deficient η5‐cyclopentadienyl)rhodium(III) complex is a highly active precatalyst for the oxidative annulation of anilides with internal alkynes under ambient conditions (at room temperature under air). A preference for annulation across electron‐rich substrates over electron‐deficient substrates was observed using this electron‐deficient rhodium(III) complex.
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