A family of isoreticular chiral metal-organic frameworks (CMOFs) of the primitive cubic network topology was constructed from [Zn(4)(μ(4)-O)(O(2)CR)(6)] secondary building units and systematically elongated dicarboxylate struts that are derived from chiral Mn-Salen catalytic subunits. CMOFs 1-5 were synthesized by directly incorporating three different chiral Mn-Salen struts into the frameworks under solvothermal conditions, and they were characterized by a variety of methods, including single-crystal X-ray diffraction, PXRD, TGA, and (1)H NMR. Although the CMOFs 1 vs 2 and CMOFs 3 vs 4 pairs were constructed from the same building blocks, they exhibit two-fold interpenetrated or non-interpenetrated structures, respectively, depending on the steric sizes of the solvents that were used to grow the MOF crystals. For CMOF-5, only a three-fold interpenetrated structure was obtained due to the extreme length of the Mn-Salen-derived dicarboxylate strut. The open channel and pore sizes of the CMOF series vary systematically, owing to the tunable dicarboxylate struts and controllable interpenetration patterns. CMOFs 1-5 were shown to be highly effective catalysts for asymmetric epoxidation of a variety of unfunctionalized olefins with up to 92% ee. The rates of epoxidation reactions strongly depend on the CMOF open channel sizes, and the catalytic activities of CMOFs 2 and 4 approach that of a homogeneous control catalyst. These results suggest that, although the diffusion of bulky alkene and oxidant reagents can be a rate-limiting factor in MOF-catalyzed asymmetric reactions, the catalytic activity of the CMOFs with large open channels (such as CMOFs 2 and 4 in the present study) is limited by the intrinsic reactivity of the catalytic molecular building blocks. The CMOF catalysts are recyclable and reusable and retain their framework structures after epoxidation reactions. This work highlights the potential of generating highly effective heterogeneous asymmetric catalysts via direct incorporation of well-defined homogeneous catalysts into framework structures of MOFs.

The cleavage of C-C bonds has been a great challenge owing to their thermodynamic and kinetic stability. To date, the progress made in this area has mainly relied on the reaction of small rings, which is driven by releasing ring strain. Encouragingly, more and more examples of the cleavage of non-strained C-C bonds have been reported. This review provides a comprehensive overview of the transition-metal-catalyzed C-C bond activation of relatively stable and unstrained molecules that involves the formation of organometallic intermediates. In the first section we focus on the C-C bond activation achieved through β-carbon elimination, and in the second section the oxidative addition of the C-C bond to low-valent metal is summarized in detail.

A chiral metal-organic framework (MOF) of the lcy topology was constructed from the Mn-Salen derived dicarboxylic acid and the [Zn(4)(μ(4)-O)(O(2)CR)(6)] secondary building unit, and used in highly regio- and stereo-selective sequential alkene epoxidation/epoxide ring-opening reactions.

[reaction: see text] The gold-catalyzed cyclization of (Z)-enynols offers an efficient and straightforward route to stereodefined (Z)-5-ylidene-2,5-dihydrofurans and fully substituted furans under extremely mild reaction conditions. Importantly, the results indicated that both the oxyauration and the proto-demetalation steps are highly stereoselective.

A highly efficient carbon-carbon triple bond cleavage reaction of (Z)-enynols was developed, which offered a new route to highly substituted butenolides. The methodology is realized by a tandem reaction using a single gold(I) catalyst, which could catalyze different reactions of cyclization/oxidative cleavage in the same vessel.

Doubling up: a chemo- and regioselective oxidative cross-coupling between various N-heteroarene-containing arenes and heteroarenes has been carried out by rhodium- or ruthenium-catalyzed twofold C-H activation, to deliver an array of highly functionalized π-conjugated systems.

Double role: A traceless directing group also acts as an internal oxidant in a novel Rh(III) -catalyzed protocol developed for the synthesis of ortho-alkenylated tertiary anilines. A five-membered cyclometalated Rh(III) complex is proposed as a plausible intermediate and confirmed by X-ray crystallographic analysis.

We have developed for the first time a general, concise and highly selective method for the C2heteroarylation of pyridines and related azines with a broad range of heteroarenes via a two-fold C-H activation, which streamlines the previous approaches that require the activated azine N-oxide as the coupling partner.Scheme 1 Selected medicinal and natural molecules containing 2-heteroarylated pyridines.