A Stereospecific Route to 6-Substituted-7-Azabicyclo[3.2.1]Oct-2-Ones

N-carbethoxy-3-exo- or 3-endo-substituted-2-azabicyclo-[2.2.2]oct-5-enes 1 provide the title compounds 2 by a stercospecific route involving bromohydrin formation, reductive dehalogenation and oxidation.     

A Facile Approach to Optically Active Hydroquinoline‐2‐carboxylates by a One‐Pot Asymmetric Michael/Transamination/Cyclization Process

An efficient one‐pot synthesis of optically active hydroquinoline‐2‐carboxylates from 1,3‐cyclohexanediones, β,γ‐unsaturated α‐keto ester, and benzylamine in the presence of a chiral base catalyst and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) with good diastereoselectivity and high enantioselectivity is described. The reaction proceeds by a sequential asymmetric Michael/transamination/cyclization process.     

The DMSO Solvated octahedro-[W6Cl]Cl Cluster Molecule

Octahedro-hexatungsten octadecachloride, W₆Cl₁₈, is soluble in dimethyl sulfoxide (DMSO). Brownish black crystals of W₆Cl₁₈(DMSO)₄ are formed from the brown solution by evaporation of DMSO under dynamic vacuum. The compound crystallizes monoclinically in the space group P2₁/n (no. 14) with a = 10.420 Å, b = 9.271 Å, c = 20.828 Å, β = 91.10° and Z = 2. The crystal structure is formed by isolated cluster molecules [W₆Cl]Cl of the hexameric tungsten trichloride and DMSO molecules. It is the first hierarchical variant of the tetragonal BaAl₄ type of structure where all atoms of the intermetallic phase are substituted by neutral molecules. The mean bond lengths are d(W–W) = 2.878 Å, d(W–Clⁱ) = 2.391 Å and d(W–Cl^a) = 2.447 Å. They will be discussed in relation to analogous clusters. The two crystallographically independent DMSO molecules (d(S–O) = 1.53–1.55 Å, d(S–C) = 1.65–1.78 Å) form a 3 D net of condensed < 4⁸6⁴ > dodecahedra which envelopes the clusters.     

5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的新法合成

以2,6-二氯吡啶为起始原料,经肼基化、还原、硝化、Nietzki-Dietschy环合4步反应得到5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物.结合反应机理讨论了还原、硝化、Nietzki-Dietschy环合反应的影响因素,获得了合成-.氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的最佳工艺条件,目标产物的总收率为59.2%.用1H NMR、MS和IR谱对5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的结构进行了表征.     

trans‐Symmetric Dynamic Covalent Systems: Connected Transamination and Transimination Reactions

The development of chemical transaminations as a new type of dynamic covalent reaction is described. The key 1,3‐proton shift is under complete catalytic control and can be conducted orthogonally to, or simultaneous with, transimination in the presence of an amine to rapidly yield two‐dimensional dynamic systems with a high degree of complexity evolution. The transamination–transimination systems are proven to be fully reversible, stable over several days, compatible with a range of functional groups, and highly tunable. Kinetic studies show transamination to be the rate‐limiting reaction in the network. Furthermore, it was discovered that readily available quinuclidine is a highly potent catalyst for aldimine transaminations. This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity‐generating element.     

A New Pyridoxal Derivative for Transamination of N‐Terminus of Proteins

A new pyridoxal‐5‐phosphate (PLP) derivative FHMDP was developed for the transamination of different peptides with three most hindered amino acid residues (Leu, Ile, Val) as their N‐terminus. Compared to the previously reported reactions of PLP derivatives, the N‐terminus transamination could be accomplished efficiently with the new compound.     

A Novel Octahedral Hexasilver(I) Cluster: Ag_6[SSCN(n-C_4H_9)_2]_6

ＣｏｍｐｏｕｎｄｓｆｏｒｍｅｄｆｒｏｍＣｕ ,ＡｇａｎｄＡｕｗｉｔｈｄｉｔｈｉｏ ｌａｔｅｌｉｇａｎｄｓ ,ｓｕｃｈａｓｔｈｅｄｉａｌｋｙｌｄｉｔｈｉｏｃａｒｂａｍａｔｅ (ＤＴＣ) ,ｍｅｒｃａｐｔｏｔｈｉａｚｏｌｉｎｅ (ＨＭＴ)ａｎｄｄｉａｌｋｙｌｄｉｔｈｉｏｐｈｏｓｐｈａｔｅｓ(ＤＤＰ) ,ｈａｖｅｐｌａｙｅｄａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｔｅｃｈｎｏｌｏｇｙ .1Ｃｕ(Ｉ) Ｓｃｌｕｓｔｅｒｓａｌｓｏｈａｖｅｂｅｅｎｉｍｐｌｉｃａｔｅｄｉｎｂｉｏｌｏｇｙａｓａｎ ｔｉ ｏｘｉｄａｎｔｓ .2Ｔｈｅｃｕｂａｎ…     

A Novel Octahedral Hexasilver（I） Cluster： Ag[SSCN（n—C4H9）2]6

The first crystal structural report of a AgDTC complex (DTC-dialkyldithiocarbamate,R=n-butyl)presented in this paper shows that it is a hexanuclear species.The structural arrangement for the DDP(dialkyldithiophosphate)ligands is different from that of Cu6(DDP)6,but is the same as that of Ag6-[SSP(O-i-Pr)2]6.     

A Mild and Regioselective Route to Functionalized Quinazolines

A Rh‐catalyzed ortho‐amidation cyclocondensation sequence gave a range of 4‐aminoquinazolines in high yield. The method features a remarkably mild C(sp²)?H activation step and can be exploited to rapidly access compounds with established biological activity.     

The Remarkably Robust,Photoactive Tungsten Iodide Cluster [W6I12(NCC6H5)2]

The new heteroleptic tungsten iodide cluster compound [W₆I₁₂(NCC₆H₅)₂] is presented. The synthesis is carried-out from Cs₂W₆I₁₄ and ZnI₂ under solvothermal conditions in benzonitrile solution, yielding red cube-shaped crystals. [W₆I₁₂(NCC₆H₅)₂] represents a heteroleptic [W₆I₈]-type cluster bearing four apical iodides and two benzonitrile ligands. Molecular [W₆I₁₂(NCC₆H₅)₂] clusters form a robust hydrogen bridged crystal structure with high thermal stability and high resistibility against hydrolysis. The electronic structure is analyzed by quantum chemical methods of the calculated electron localization function (ELF) and the band structure. Photoluminescence measurements are performed to verify and describe the photophysical properties of [W₆I₁₂(NCC₆H₅)₂]. Finally, the photocatalytic properties of [W₆I₁₂(NCC₆H₅)₂] are evaluated as a proof-of-concept.     

Crystal and molecular structure of two calix[6]arenes:p-Isopropylcalix[6]arene andp-tert-butylcalix[6]arene—benzene(1∶3) complex

The isopropyl derivative crystallizes from a mixture of carbon disulfide and benzene in the orthorhombic system: Space groupP2₁ nb, a=17.420(3),b=17.708(3),c=18.972(3) Å,V=5852(3) Å,Z=4. Thet-butyl derivative crystallizes from benzene, but the crystal is a complex (13), space groupP,a=15,065(5),b=19.103(3),c=13.878(3) Å, =106.95(2), =102.72(2), =80.61(2),V=3703(2) ų,Z=2. Refinement led toR=0.185 for 1512 reflections for the isopropyl derivative, a sufficiently high number to establish the conformation of the molecule; for thet-butyl complexR=0.12 for 7340 reflections. Intramolecular hydrogen bonds are given as well as comparison of the conformation of both compounds. Thet-butyl groups and the benzene molecules are disordered but the isopropyl groups are not. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82071 (57 pages).     

5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的合成新方法

以2,6-二氯吡啶为起始原料, 经肼基化、还原、硝化、Nietzki-Dietschy环合4步反应得到5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物。 结合反应机理讨论了还原、硝化、Nietzki-Dietschy环合反应的影响因素,获得了合成5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的最佳工艺条件,目标产物的总收率为59.2%。 用1H NMR、MS和IR谱对5-氨基-6-硝基-[1,2,5]噁二唑并[3,4-b]吡啶-1-氧化物的结构进行了表征。     

A Photochemical Macrocyclization Route to Asymmetric Strained [3.2] Paracyclophanes

The intricate frameworks of paracyclophanes are an important target for synthesis since they are found in various chiral auxiliaries, solar cells, high-performance plastics, pharmaceuticals, and molecular machines. Whereas numerous methods exist for the preparation of symmetric paracyclophanes, protocols for the efficient synthesis of strained asymmetric scaffolds are limited. Here we report a remarkably simple photochemical route to strained [3.2]paracyclophanes starting from readily available educts. By way of NMR and X-ray analyses, we discovered that UV-irradiation of an aromatic carboxylic ester tethered to a toluene moiety leads to the intramolecular formation of a new C−C bond, with loss of an alcohol. A systematic evaluation of the reaction conditions and substituents, as well as radical starter and triplet quenching experiments, point to a reaction mechanism involving an excited triplet state and hydrogen atom transfer. The new method proved to be robust and versatile enabling the synthesis of a range of cyclophanes with different substitutions, including an unusual diastereoisomer with two planar chiral centers, and thus proved to be a valuable addition to the synthetic toolbox.     

A Photochemical Route to 2-Substituted Benzo[b]furans

2-Substituted benzo[b]furans were synthesized by a one-step metal-free photochemical reaction between 2-chlorophenol derivatives and terminal alkynes by tandem formation of an aryl-C and a C-O bond via an aryl cation intermediate. The mild conditions and the application to chlorophenols rather of the more expensive bromo or iodo analogues makes this procedure environmentally convenient.     

The Cluster Compounds Ag[W6Br14] and Ag2[W6Br14]

The reaction of W₆Br₁₂ with AgBr in evacuated silica tubes (temperature gradient 925 K/915 K) yielded brownish black octahedra of Ag[W₆Br₁₄] ( I ) and yellowish green platelets of Ag₂[W₆Br₁₄] ( II ) both in the low temperature zone. ( I ) crystallizes cubically (Pn3 (no. 201); a = 13.355 Å, Z = 4) and ( II ) monoclinically (P2₁/c (no. 14); a = 9.384 Å, b = 15.383 Å, c = 9.522 Å, β = 117.34°, Z = 2). Both crystal structures contain isolated cluster anions, namely [(W₆Brⁱ₈)Br^a₆]^1– and [(W₆Brⁱ₈)Br^a₆])]^2–, respectively, with the mean distances and angles: ( I ) d(W–W) = 2.648 Å, d(W–Brⁱ) = 2.617 Å, d(W–Br^a) = 2.575 Å, d(Brⁱ…Brⁱ) = 3.700 Å, d(Brⁱ…Br^a) = 3.692 Å, ∠W–Brⁱ–W = 60.78°. ( II ) d(W–W) = 2.633 Å, d(W–Brⁱ) = 2.624 Å, d(W–Br^a) = 2.613 Å, d(Brⁱ…Brⁱ) = 3.710 Å, d(Brⁱ…Br^a) = 3.707 Å, ∠W–Brⁱ–W = 60.23°. The Ag⁺ cations are trigonal antiprismatically coordinated in ( I ) with d(Ag–Br) = 2.855 Å, but distorted trigonally planar in ( II ) with d(Ag–Br) = 2.588–2.672 Å. The structural details of hitherto known compounds with [W₆Br₁₄] anions will be discussed.