: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The development of new methods for the direct functionalization of unactivated C–H bonds is ushering in a paradigm shift in the field of retrosynthetic analysis. In particular, the catalytic enantioselective functionalization of C–H bonds represents a highly atom- and step-economic approach toward the generation of structural complexity. However, as a result of their ubiquity and low reactivity, controlling both the chemo- and stereoselectivity of such processes constitutes a significant challenge. Herein we comprehensively review all asymmetric transition-metal-catalyzed methodologies that are believed to proceed via an inner-sphere-type mechanism, with an emphasis on the nature of stereochemistry generation. Our analysis serves to document the considerable and rapid progress within in the field, while also highlighting limitations of current methods.

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Catalytic Enantioselective Transformations Involving C-H Bond Cleavage by Transition-Metal Complexes.

ConspectusTransition-metal catalyzed C–H functionalizations became a complementary and efficient bond-forming strategy over the past decade. In this respect, Cp*Rh(III) complexes have emerged as powerful catalysts for a broad spectrum of reactions giving access to synthetically versatile building blocks. Despite their high potential, the corresponding catalytic enantioselective transformations largely lag behind. The targeted transformations require all the remaining three coordination sites of the central rhodium atom of the catalyst. In consequence, the chiral information on a competent catalyst can only by stored in the cyclopentadienyl unit. The lack of suitable enabling chiral cyclopentadienyl (Cpx) ligands is the key hurdle preventing the development of such asymmetric versions. In this respect, an efficient set of chiral Cpx ligands useable with a broad variety of different transition-metals can unlock substantial application potential. This Account provides a description of our developments of two...

Chiral Cyclopentadienyls: Enabling Ligands for Asymmetric Rh(III)-Catalyzed C–H Functionalizations

During the past decades, synthetic organic chemistry discovered that directing group assisted C–H activation is a key tool for the expedient and siteselective construction of C–C bonds. Among the v...

Bidentate Directing Groups: An Efficient Tool in C-H Bond Functionalization Chemistry for the Expedient Construction of C-C Bonds.

Axial chirality is a key feature of many important organic molecules, such as biologically active compounds, stereogenic ligands and optically pure materials. Significant efforts in the field of the atropisomeric synthesis of biaryls have hence been undertaken over the past decade. Several major improvements of the already known methods to build up such chiral backbones (e.g. oxidative couplings and stereoselective Suzuki–Miyaura arylations) have been achieved and, in parallel, novel concepts have emerged enabling unprecedented synthetic routes toward molecules of this kind. These outstanding steps further unlocked the door to the preparation of previously difficult-to-access precursors of privileged ligands like BINOL, BINAM, QUINAP and many other molecules of interest.

Recent advances and new concepts for the synthesis of axially stereoenriched biaryls

The vastly increasing application of chiral Cp ligands in asymmetric catalysis results in growing demand for novel chiral Cp ligands. Herein, we report a new class of chiral Cp ligands based on 1,1'-spirobiindane, a privileged scaffold for chiral ligands and catalysts. The corresponding Rh complexes are shown to be excellent catalysts in asymmetric oxidative coupling reactions, providing axially chiral biaryls in 19-97% yields with up to 98:2 er.

Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes

A Rh-catalyzed enantioselective dearomatization of 1-aryl-2-naphthols with internal alkynes via C–H functionalization reaction was achieved. In the presence of a chiral Cp/Rh catalyst and combined oxidants of Cu(OAc)2 and air (oxygen), various highly enantioenriched spirocyclic enones bearing an all-carbon quaternary stereogenic center could be synthesized in 33–98% yields with up to 97:3 er.

Asymmetric Dearomatization of Naphthols via a Rh-Catalyzed C(sp²)-H Functionalization/Annulation Reaction.

Enantioselective construction of axially chiral biaryls by direct CH bond functionalization reactions has been realized. Novel axially chiral biaryls were synthesized by the direct CH bond olefination of biaryl compounds, using a chiral [Cp*RhIII] catalyst, in good to excellent yields and enantioselectivities. The obtained axially chiral biaryls were found as suitable ligands for rhodium-catalyzed asymmetric conjugate additions.

Construction of Axial Chirality by Rhodium‐Catalyzed Asymmetric Dehydrogenative Heck Coupling of Biaryl Compounds with Alkenes

Rhodium-catalyzed C(sp2)−H functionalization reactions of 4-aryl-5-pyrazolones followed by [3+2] annulation reactions with alkynes provide rapid access to highly enantioenriched five-membered-ring 4-spiro-5-pyrazolones. The use of a chiral SCpRh catalyst enabled the synthesis of a large range of spiropyrazolones with all-carbon quaternary stereogenic centers in up to 99 % yield and 98 % ee from readily available substrates.

Asymmetric Synthesis of Spiropyrazolones by Rhodium-Catalyzed C(sp2 )-H Functionalization/Annulation Reactions.

An organocatalytic asymmetric chlorinative dearomatization of naphthols was realized for the first time, providing chiral naphthalenones with a Cl-containing all-substituted stereocenter in excellent yields and enantioselectivity (up to 97% yield and 96% ee). The reaction features mild reaction conditions, good tolerance of diverse functional groups and simple reaction operation.

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Jun Zheng

Papers

Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes

Asymmetric Dearomatization of Naphthols via a Rh-Catalyzed C(sp²)-H Functionalization/Annulation Reaction.

Construction of Axial Chirality by Rhodium‐Catalyzed Asymmetric Dehydrogenative Heck Coupling of Biaryl Compounds with Alkenes

Asymmetric Synthesis of Spiropyrazolones by Rhodium-Catalyzed C(sp2 )-H Functionalization/Annulation Reactions.

Organocatalytic asymmetric chlorinative dearomatization of naphthols