A AgF‐mediated fluorination with a concomitant cross‐coupling between a gem‐difluoroolefin and a non‐fluorinated olefin is reported. This highly efficient method provides facile access to both α‐CF3 alkenes and β‐CF3 ketones, which otherwise remain challenging to be directly prepared. The application of this method is further demonstrated by the synthesis of bioactive isoxazoline derivatives. This approach represents a conceptually novel route to trifluoromethylated compounds that combines the in situ generation of the CF3 moiety and a C? H functionalization in a single reaction system. 相似文献
The investigated crystal of α‐LiRb2(CF3SO3)3 [lithium dirubidium tris(trifluoromethanesulfonate)] was a twin, with the twin matrix given by (00/010/001). The structure consists of channel‐like patterns built up of lipophilic CF3 groups pointing towards each other. The polar interstices are occupied by cations. One Rb atom is coordinated by O atoms in the form of a distorted square antiprism, while the coordination around the second Rb atom is best described as a distorted pentagonal plane, with one O atom and one F atom situated above and an additional F atom below this plane. The O atoms around the Li atom form a strongly distorted tetrahedron. 相似文献
Despite the burgeoning demand for fluorine‐containing chemical entities, the construction of CF3‐containing stereogenic centers has remained elusive. Herein, we report the strategic merger of CuI/base‐catalyzed enolization of an α‐CF3 amide and Pd0‐catalyzed allylic alkylation in an enantioselective manner to deliver chiral building blocks bearing a stereogenic carbon center connected to a CF3, an amide carbonyl, and a manipulable allylic group. The phosphine complexes of CuI and Pd0 engage in distinct catalytic roles without ligand scrambling to render the dual catalysis operative to achieve asymmetric α‐allylation of the amide. The stereoselective cyclization of the obtained α‐CF3‐γ,δ‐unsaturated amides to give tetrahydropyran and γ‐lactone‐fused cyclopropane skeletons highlights the synthetic utility of the present catalytic method as a new entry to non‐racemic CF3‐containing compounds. 相似文献
A concise protocol for the synthesis of α‐methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams has been described via alkylation of amino acid derived iminoesters with α‐bromomethylmethacrylate, followed by allylic hydroxylation. All the synthesized compounds have been evaluated for their cytotoxicity on multiple myeloma cancer cell lines. 相似文献
A concise synthesis of α‐benzylidene‐γ‐methyl‐γ‐butyrolactones 5a – g from substituted benzaldehydes is described. Compounds 1a – g on reaction with phosphorane 2 , provide the pentenoates 3a – g , which can be hydrolyzed to the acids 4a – g . The latter are cyclized to the corresponding butyrolactones 5a – g in excellent yields. The pentenoates 3a – g , on acid catalyzed cyclization, also provide 5a – g in very high yields. 相似文献
A preparatively useful one‐step transformation of γ,γ‐disubstituted α‐formyl‐γ‐lactones into trisubstituted γ,δ‐unsaturated aldehydes is described, by means of catalytic amounts of either AcOH or AcOEt in the vapor phase over a glass support. A mechanistic rationale is proposed. 相似文献
A direct and convenient method has been developed for the synthesis of optically active pyrrolidines bearing a quaternary stereogenic center containing a CF3 group at the C‐3 position of the pyrrolidine ring. The synthesis system, CuI/Si‐FOXAP‐catalyzed exo‐selective 1,3‐dipolar cycloaddition of azomethine ylides with β‐CF3‐β,β‐disubstituted nitroalkenes, provides pyrrolidines with high diastereoselectivities (up to >98:2 d.r.) and excellent enantioselectivities (up to >99.9 ee) and performs well for a broad scope of substrates under mild conditions. 相似文献
In the title compounds, C21H30O4, (I), and C23H34O4, (II), respectively, which are valuable intermediates in the synthesis of important steroid derivatives, rings A and B are cis‐(5β,10β)‐fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5β,6β‐epoxide group induces a significant twist of the steroid nucleus and a strong flattening of the B ring. The different C17 substituents result in different conformations for ring D. Cohesion of the molecular packing is achieved in both compounds only by weak intermolecular interactions. The geometries of the molecules in the crystalline environment are compared with those of the free molecules as given by ab initio Roothan Hartree–Fock calculations. We show in this work that quantum mechanical ab initio methods reproduce well the details of the conformation of these molecules, including a large twist of the steroid nucleus. The calculated twist values are comparable, but are larger than the observed values, indicating a possible small effect of the crystal packing on the twist angles. 相似文献
The title compounds, both C23H34O5, are the 5α and 5β configurations of two diacetate epimers. The 5β‐diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 Å3, responsible for clathrate behaviour. The 5β‐epimer also features some shorter than average bond lengths in the 3α,4β‐acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through abinitio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C—H⋯O interactions. 相似文献
13‐cis‐β,β‐Carotene, C40H56, crystallizes with a complete molecule in the asymmetric unit, whereas 15‐cis‐β,β‐carotene, also C40H56, has twofold symmetry about an axis through the central bond of the polyene chain. The polyene methyl groups are arranged on one side of the polyene chains for each molecule and the 6‐s‐cisβ end groups, with the cyclohexene rings in half‐chair conformations, are twisted out of the planes of the polyene chains by angles ranging from 41.37 (17) to 52.2 (4)°. The molecules in each structure pack so that the arms of one occupy the cleft of the next, and there is significant π–π stacking of the almost‐parallel polyene chains of the 15‐cis isomer, which approach at distances of 3.319 (1)–3.591 (1) Å. 相似文献
A convenient route with high stereo control to γ‐acetoxy dienoates is provided by the reaction of methyl propiolate with aldehydes in the presence of ZnEt2 and N‐methylimidazole at room temperature, followed by the catalytic conversion of the resulting γ‐hydroxy‐α,β‐acetylenic esters with p‐N,N‐dimethylaminopyridine (DMAP) in acetic anhydride (see scheme).