Continuous organocatalysis : Fast aldol and Mannich reactions require less catalyst when conducted in a microreactor. A proline tetrazole derivative (5–10 mol %) catalyzes asymmetric aldol reactions between various aromatic aldehydes and ketones in microreactor at 60 °C with reaction times ranging from 10 to 30 min.
The moderate nucleophilicity of the axially chiral amino sulfonamide (S)‐ 1 suppresses the problematic side reactions, including aldol reactions, in the asymmetric Mannich reaction of N‐Boc‐protected imines with aldehydes. The corresponding adducts are obtained in good yield and excellent stereoselectivity (see scheme; Boc=tert‐butoxycarbonyl, Tf=trifluoromethanesulfonyl).
Positive discrimination : Chemo‐ and regioselective palladium‐catalyzed cycloetherification of allendiols, namely β,γ‐ and γ,δ‐allendiols, may occur by judicious choice of palladium‐catalyzed conditions owing to their potential ability to discriminate between both nucleophilic sites (see scheme).
In control : A new catalytic vinylogous Mukaiyama aldol reaction provides products with high diastereo‐ and enantioselectivities (up to 99 % de and ee; see scheme). The relative and absolute stereochemistry of a representative product was rigorously assigned by NMR and CD spectroscopies (measured and calculated), X‐ray diffraction, and quantum‐chemical calculations.
Double‐cross : Proline catalyzes the double Mannich reaction of acetaldehyde with N‐Boc imines in excellent yields (up to 99 %; Boc=tert‐butoxycarbonyl) and close to perfect diastereo‐ and enantioselectivities. Depending on the choice of catalysts, both the chiral, pseudo‐C2‐symmetric diastereomer and the corresponding meso compound can be prepared. Cross double Mannich reactions of acetaldehyde with two different imines are also demonstrated.
W415 is a chiral smectic compound with a remarkably weak temperature dependence of its giant electroclinic effect in the liquid crystalline smectic A* phase. Furthermore it possesses a high spontaneous polarization in the smectic C* phase. The origin of this striking electroclinic effect is the co‐occurrence of a de Vries‐type ordering with a weak first‐order tilting transition (see the synchroton X‐ray scattering profiles).
Awakening of the Cp one : The bifunctional complex 1 facilitates the interaction with substrates bearing less electrophilic carbon atoms than ketones, epoxides, and imides. The title reaction was applicable to the reduction of Evans' asymmetric alkylation products to the chiral alcohols along with good recovery of the chiral oxazolidinone auxiliary. EWG=electron‐withdrawing group.
Different in water! We have developed Nazarov‐type reactions in water. Different reaction courses compared with those in organic solvents are observed in water. In the presence of a scandium based, surfactant‐type catalyst, water‐trapping products are obtained exclusively. The results presented are unprecedented and provide a valuable extension to information available regarding organic reactions in water.
Mild reaction conditions are the advantage of the title reaction, which allows straightforward entry to a variety of ynamides starting from readily available 1,1‐dibromo‐1‐alkenes, which act as attractive alkynylating agents (see scheme; EWG=electron‐withdrawing group, DMF=N,N‐dimethylformamide).
Switching characteristics: The 633 nm wavelength of an He–Ne laser is used to fabricate holographic transmission gratings in polymer‐dispersed liquid‐crystal cells. The microstructure and diffraction efficiency (η) both improve with increasing functionality (see figure). For functionalities of 2.5 or more, η approaches 34 % and can be switched off with electric fields of about 20 MV m?1.
Single‐site catalysts : Syndiospecific styrene polymerization promoted by single‐site ansa‐lanthanidocene catalysts proceeds selectively in a secondary (2,1) fashion, both at the initiation and propagation steps. The steric hindrance between the phenyl ring of the incoming styrene monomer and the ancillary ligands (Cp′, Flu′), induced by the change of either the bridge or the “active” R ligand in the catalyst precursor, is proposed to control the reactivity of the complexes (see scheme).
A practical and sustainable chemical process for the synthesis of highly substituted aldol?lactol products was achieved for the first time through the asymmetric Barbas–List aldol (BLA) reaction of 2‐hydroxybenzaldehydes with acetone in the presence of a catalytic amount of trans‐4‐OH‐L ‐proline (see scheme).
It′s a PTC : A highly efficient reaction of 3‐aryloxindoles in an asymmetric Michael addition was achieved by using a quaternary tetraalkylphosphonium salt as a chiral phase‐transfer catalyst (PTC). The products were obtained in quantitative yields high ee values. The reaction of 3‐aryloxindoles in an asymmetric Mannich reaction using the same catalyst also proved to be feasible.
Sailing the seven ‘C's : 2,2,3‐Trimethylbutane (triptane) selectively forms from dimethyl ether at low temperatures on acid zeolites. Selective methylation at less‐substituted carbons, relative rates of methylation to hydrogen transfer as a function of chain size, slow skeletal isomerization, and β‐scission cracking of triptyl chains and their precursors are intrinsic properties of carbenium ions and account for the remarkable triptane selectivities within C7 .
Efficient route : A novel RhI‐catalyzed regio‐ and stereospecific carbonylation reaction of (1‐alkynyl)cyclopropyl ketones by selective activation of a carbon? carbon σ bond of the cyclopropane ring was demonstrated (see scheme). This method provides a general, efficient, stereoselective route to synthesise 1,3,5‐trisubstituted and 1,3,5,6‐tetrasubstituted 5,6‐dihydrocyclopenta[c]furan‐4‐one with convertible functional groups.
Arene control : Anticancer complexes [Ru(arene)Cl(en)]+ (arene=p‐cymene or biphenyl; en=ethylenediamine) bind to surface histidine (His128, His247, His510) and methionine (Met298) residues in human albumin, but only the p‐cymene complex can gain entry to the crevice containing the free cysteine thiolate (Cys34) and induce oxidation to sulfinate.
Broken‐symmetry DFT calculations on transition‐metal clusters with more than two centers allow the hyperfine coupling constants to be extracted. Application of the proposed theoretical scheme to a tetranuclear manganese complex that models the S2 state of the oxygen‐evolving complex of photosystem II yields hyperfine parameters that can be directly compared with experimental data. The picture shows the metal–oxo core of the model and the following parameters; exchange coupling constant Jij, the expectation value of the site‐spin operator , and the isotropic hyperfine coupling parameters.
An old dream comes true : A direct and environmentally benign synthetic strategy was developed for the aerosol‐based mass production of large‐pore mesostructured aluminosilicate powders (see TEM image). Although amorphous, some powders exhibit higher activity towards m‐xylene isomerization and lower coke formation than a Y‐zeolite based industrial reference catalyst.
Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
