An efficient Cp*CoIII‐catalyzed C8‐dienylation of quinoline‐N‐oxides was achieved by employing allenes bearing leaving groups at the α‐position as the dienylating agents. The reaction proceeds by CoIII‐catalyzed C?H activation of quinoline‐N‐oxides and regioselective migratory insertion of the allene followed by a β‐oxy elimination, leading to overall dienylation. Site‐selective C?H activation was achieved with excellent selectivity under mild reaction conditions, and 30 mol % of a NaF additive was found to be crucial for the efficient dienylation. The methodology features high stereoselectivity, mild reaction conditions, and good functional‐group tolerance. C8‐alkenylation of quinoline‐N‐oxides was achieved in the case of allenes devoid of leaving groups as coupling partners. Furthermore, gram‐scale preparation and preliminary mechanistic experiments were carried out to gain insights into the reaction mechanism. 相似文献
Indoles and their analogues have been one of the most ubiquitous heterocycles during the past century, and extensive studies have been conducted to establish practical synthetic methods for their derivatives. In particular, selective functionalization of the poorly reactive benzenoid core over the pyrrole ring has been a great challenge. Reported herein is an iridium‐catalyzed direct alkynylation of the indole C4‐ and C7‐positions with the assistance of sulfur directing groups. This transformation shows a wide range of functional‐group tolerance with exceptional site selectivity. The directing group can be either easily removed or transformed after catalysis. The synthetic utility of the alkyne fragment is demonstrated by the derivatization into the core structure of natural indole alkaloids. 相似文献
A solvent‐controlled C2/C5‐selective alkenylation of 3,4‐disubstituted pyrroles has been developed. The C3 substituent of pyrroles proved crucial to the regioselectivity. Substrates bearing directing groups at the C3 position exhibited excellent C2‐selectivities in chelation‐assisted C?H activation in toluene or 1,4‐dioxane. However, a DMSO/DMF solvent system could override the chelation effect of weak directing groups, such as carboxylate and carbonyl groups, favoring instead regioselectivity towards the more electron‐rich C5 position. A series of 3‐carboxylate and 3‐carbonyl pyrroles were tested and showed moderate to good yields with good regioselectivities for both C2‐ and C5‐alkenylation process. 相似文献
Decylammonium tetrachlorozincate (n‐C10H21NH3)2ZnCl4(C10ZnCl), dodecylammonium tetrachlorozincate (n‐C12H25NH3)2ZnCl4(C12ZnCl) and hexadecylammonium tetrachlorozincate (n‐C16H33NH3)2ZnCl4‐(C16ZnCl) were synthesized and a series of their mixtures C10ZnCl‐C16ZnCl and C12ZnCl‐C16ZnCl were prepared. The experimental binary phase diagrams of C10ZnCl‐C16ZnCl and C12ZnCl‐C16ZnCl were established by means of differential scanning calorimetry (DSC), IR and X‐ray diffraction. In the phase diagram a stable solid compound and two eutectoid invariants were observed. It is noticeable that the phase diagram contains solid solution ranges. 相似文献
A catalytic enantioselective route to C1‐ and C2‐symmetric 2,2′‐spirobiindanones has been realized through an intramolecular enolate C‐acylation. This reaction employs a chiral ammonium counterion to direct the acylation of an in situ generated ketone enolate with a pentafluorophenyl ester. This reaction constitutes the first example of a direct catalytic enantioselective C‐acylation of a ketone and provides an efficient and highly enantioselective route to axially chiral spirobiindanediones. These products can be diastereoselectively derivatized, offering access to a range of functionalized spirocyclic architectures. 相似文献
An efficient rhodium‐catalyzed method for direct C? H functionalization at the C7 position of a wide range of indoles has been developed. Good to excellent yields of alkenylation products were observed with acrylates, styrenes, and vinyl phenyl sulfones, whereas the saturated alkylation products were obtained in good yield with α,β‐unsaturated ketones. Both the N‐pivaloyl directing group and the rhodium catalyst proved to be crucial for high regioselectivity and conversion. 相似文献
Pale yellow single crystals of [O=C(NPPh3)C(I)=C(NPPh3)‐C(NPPh3)2]+I‐·1.5 thf ( 1 ·1.5 thf) have been obtained by the reaction of INPPh3 with thallium in thf suspension. They are characterized by IR spectroscopy and by a crystal structure determination. 1 ·1.5 thf crystallizes in the monoclinic space group P21/n, Z = 4, lattice dimensions at ‐83?C: a = 1101.7(1), b = 3449.0(2), c = 2000.4(1) pm, β = 104.88(1)?, R1 = 0.0382. 1 can be understood as a cationic variation of (Z)‐2‐butenale in which all H atoms are substituted by triphenylphosphoraneimine residues and by a iodine atom, respectively. 相似文献
This article describes recent developments in C3‐symmetric tris‐urea low‐molecular‐weight gelators and their applications. The C3‐symmetric tris‐ureas are excellent frameworks to form supramolecular polymers through noncovalent interactions. In organic solvents, hydrophobic tris‐ureas form supramolecular gels. Amphiphilic tris‐ureas form supramolecular gels in aqueous media. Functional supramolecular gels were prepared by introducing appropriate functional groups into the outer sphere of tris‐ureas. Supramolecular hydrogels obtained from amphiphilic tris‐ureas were used in the electrophoresis of proteins. These electrophoreses results showed several unique characteristics compared to typical electrophoreses results obtained using polyacrylamide matrices.
We have used dissipative particle dynamics (DPD) to simulate the self‐assembling behavior of A‐block‐(B‐graft‐C) coil‐comb molecules, in which each B segment is covalently bonded with one C segment. In addition to the composition, we found that by varying any of the interaction parameters between each pair of components I and J, where I, J = A, B, C, we can also induce a series of morphology transitions associated with two length scales. Moreover, we observed that if the length of the BC‐comb block is not long enough, the resulting morphology is mainly in the large‐length‐scale, ordering between the A‐rich and C‐rich domains with most of the B in the interfaces. By increasing the length of the BC‐comb block, one may expect that both B and C can pack orderly to form a lamellar structure. As a result, various experimentally observed structure‐within‐structures have been simulated via DPD.
We have discovered that the racemization of configurationally stable, axially chiral 2,2′‐dihydroxy‐1,1′‐biaryls proceeds with a catalytic amount of a cyclopentadienylruthenium(II) complex at 35–50 °C. Combining this racemization procedure with lipase‐catalyzed kinetic resolution led to the first lipase/metal‐integrated dynamic kinetic resolution of racemic axially chiral biaryl compounds. The method was applied to the synthesis of various enantio‐enriched C1‐ and C2‐symmetric biaryl diols in yields of up to 98 % and enantiomeric excesses of up to 98 %, which paves the way for new developments in the field of asymmetric synthesis. 相似文献