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61.
Manool is converted into ring-B-nor analogues of commercially important perfumery compounds via a novel ring-B-nor intermediate methylene ketone 9. Compound 9 is synthesised via the formation of an exocyclic bromonium ion and the concomitant ring contraction of the B-ring of a diterpene skeleton derived from manool. Oxidation and base treatment of the ring-contracted product result in dehydrohalogenation and decarboxylation to afford methylene ketone compound 9, which is then converted to ring-B-nor analogues of Ambrox® and amberketal. 相似文献
62.
Jeremy C. Mullins Dr. K. Yuvaraj Yixiao Jiang Dr. Gerard P. Van Trieste III Dr. Asim Maity Prof. David C. Powers Prof. Cameron Jones 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(65):e202202103
UV irradiation of solutions of a guanidinate coordinated dimagnesium(I) compound, [{(Priso)Mg}2] 3 (Priso=[(DipN)2CNPri2]−, Dip=2,6-diisopropylphenyl), in either benzene, toluene, the three isomers of xylene, or mesitylene, leads to facile activation of an aromatic C−H bond of the solvent in all cases, and formation of aryl/hydride bridged magnesium(II) products, [{(Priso)Mg}2(μ-H)(μ-Ar)] 4 – 9 . In contrast to similar reactions reported for β-diketiminate coordinated counterparts of 3 , these C−H activations proceed with little regioselectivity, though they are considerably faster. Reaction of 3 with an excess of the pyridine, p-NC5H4But (pyBut), gave [(Priso)Mg(pyButH)(pyBut)2] 10 , presumably via reduction of the pyridine to yield a radical intermediate, [(Priso)Mg(pyBut⋅)(pyBut)2] 11 , which then abstracts a proton from the reaction solvent or a reactant. DFT calculations suggest two possible pathways to the observed arene C−H activations. One of these involves photochemical cleavage of the Mg−Mg bond of 3 , generating magnesium(I) doublet radicals, (Priso)Mg⋅. These then doubly reduce the arene substrate to give “Birch-like” products, which subsequently rearrange via C−H activation of the arene. Circumstantial evidence for the photochemical generation of transient magnesium radical species includes the fact that irradiation of a cyclohexane solution of 3 leads to an intramolecular aliphatic C−H activation process and formation of an alkyl-bridged magnesium(II) species, [{Mg(μ-Priso−H)}2] 12 . Furthermore, irradiation of a 1 : 1 mixture of 3 and the β-diketiminato dimagnesium(I) compound, [{(DipNacnac)Mg}2] (DipNacnac=[HC(MeCNDip)2]−), effects a “scrambling” reaction, and the near quantitative formation of an unsymmetrical dimagnesium(I) compound, [(Priso)Mg−Mg(DipNacnac)] 13 . Finally, the EPR spectrum (77 K) of a glassed solution of UV irradiated 3 is dominated by a broad featureless signal, indicating the presence of a doublet radical species. 相似文献
63.
Guoxiong Hua Cameron L. Carpenter-Warren David B. Cordes Alexandra M. Z. Slawin J. Derek Woollins 《Molecules (Basel, Switzerland)》2021,26(8)
A series of N-aryl-N-(2-oxo-2-arylethyl) benzamides and cinnamides has been prepared. The reaction of the benzamides with Woollins’ reagent, a highly efficient chemoselective selenation/reduction reagent, gave the corresponding N-aryl-N-(arylenethyl) benzoselenoamides in good yields. Five representative single crystal X-ray structures are discussed. 相似文献
64.
Platinum Complexes Containing Pyramidalized Germanium and Tin Dihalide Ligands Bound through σ,σ ME Multiple Bonds 下载免费PDF全文
Florian Hupp Dr. Mengtao Ma Franziska Kroll Dr. J. Oscar C. Jimenez‐Halla Dr. Rian D. Dewhurst Dr. Krzysztof Radacki Dr. Andreas Stasch Prof. Dr. Cameron Jones Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16888-16898
We present the isolation of the first mononuclear dihalogermylene, and mono‐ and dinuclear stannylene complexes of transition metals. These exhibit exceptionally pyramidalized Group 14 centers. Additionally, removal of the halide substituents from the Ge/Sn atom was successfully performed in two ways, halide abstraction and reduction, leading to a variety of unusual structural motifs. 相似文献
65.
Jonathan W. Dube Cameron M. E. Graham Prof. Charles L. B. Macdonald Dr. Zachary D. Brown Prof. Philip P. Power Prof. Paul J. Ragogna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6739-6744
Two unique systems based on low‐coordinate main group elements that activate P4 are shown to quantitatively release the phosphorus cage upon short exposure to UV light. This reactivity marks the first reversible reactivity of P4, and the germanium system can be cycled 5 times without appreciable loss in activity. Theoretical calculations reveal that the LUMO is antibonding with respect to the main group element–phosphorus bonds and bonding with respect to reforming the P4 tetrahedron, providing a rationale for this unprecedented activity, and suggesting that the process is tunable based on the substituents. 相似文献
66.
Experimental and Computational Studies of a Multi‐Electron Donor–Acceptor Ligand Containing the Thiazolo[5,4‐d]thiazole Core and its Incorporation into a Metal–Organic Framework 下载免费PDF全文
Felix J. Rizzuto Dr. Thomas B. Faust Dr. Bun Chan Carol Hua Dr. Deanna M. D'Alessandro Prof. Cameron J. Kepert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17597-17605
A ligand containing the thiazolo[5,4‐d]thiazole (TzTz) core (acceptor) with terminal triarylamine moieties (donors), N,N′‐(thiazolo[5,4‐d]thiazole‐2,5‐diylbis(4,1‐phenylene))bis(N‐(pyridine‐4‐yl)pyridin‐4‐amine ( 1 ), was designed as a donor–acceptor system for incorporation into electronically active metal–organic frameworks (MOFs). The capacity for the ligand to undergo multiple sequential oxidation and reduction processes was examined using UV/Vis‐near‐infrared spectroelectrochemistry (UV/Vis‐NIR SEC) in combination with DFT calculations. The delocalized nature of the highest occupied molecular orbital (HOMO) was found to inhibit charge‐transfer interactions between the terminal triarylamine moieties upon oxidation, whereas radical species localized on the TzTz core were formed upon reduction. Conversion of 1 to diamagnetic 2+ and 4+ species resulted in marked changes in the emission spectra. Incorporation of this highly delocalized multi‐electron donor–acceptor ligand into a new two‐dimensional MOF, [Zn(NO3)2( 1 )] ( 2 ), resulted in an inhibition of the oxidation processes, but retention of the reduction capability of 1 . Changes in the electrochemistry of 1 upon integration into 2 are broadly consistent with the geometric and electronic constraints enforced by ligation. 相似文献
67.
An Investigation of Photo‐ and Pressure‐Induced Effects in a Pair of Isostructural Two‐Dimensional Spin‐Crossover Framework Materials 下载免费PDF全文
Dr. Natasha F. Sciortino Dr. Suzanne M. Neville Dr. Cédric Desplanches Dr. Jean‐François Létard Dr. Victor Martinez Prof. José Antonio Real Dr. Boujemaa Moubaraki Prof. Keith S. Murray Prof. Cameron J. Kepert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7448-7457
Two new isostructural iron(II) spin‐crossover (SCO) framework (SCOF) materials of the type [Fe(dpms)2(NCX)2] (dpms=4,4′‐dipyridylmethyl sulfide; X=S ( SCOF‐6(S) ), X=Se ( SCOF‐6(Se) )) have been synthesized. The 2D framework materials consist of undulating and interpenetrated rhomboid (4,4) nets. SCOF‐6(S) displays an incomplete SCO transition with only approximately 30 % conversion of high‐spin (HS) to low‐spin iron(II) sites over the temperature range 300–4 K (T1/2=75 K). In contrast, the NCSe? analogue, SCOF‐6(Se) , displays a complete SCO transition (T1/2=135 K). Photomagnetic characterizations reveal quantitative light‐ induced excited spin‐state trapping (LIESST) of metastable HS iron(II) sites at 10 K. The temperature at which the photoinduced stored information is erased is 58 and 50 K for SCOF‐6(S) and SCOF‐6(Se) , respectively. Variable‐pressure magnetic measurements were performed on SCOF‐6(S) , revealing that with increasing pressure both the T1/2 value and the extent of spin conversion are increased; with pressures exceeding 5.2 kbar a complete thermal transition is achieved. This study confirms that kinetic trapping effects are responsible for hindering a complete thermally induced spin transition in SCOF‐6(S) at ambient pressure due to an interplay between close T1/2 and T(LIESST) values. 相似文献
68.
Time‐Resolved Assembly of Cluster‐in‐Cluster {Ag12}‐in‐{W76} Polyoxometalates under Supramolecular Control 下载免费PDF全文
Caihong Zhan Jamie M. Cameron Jing Gao Jamie W. Purcell De‐Liang Long Leroy Cronin 《Angewandte Chemie (International ed. in English)》2014,53(39):10362-10366
We report the time‐resolved supramolecular assembly of a series of nanoscale polyoxometalate clusters (from the same one‐pot reaction) of the form: [H(10+m)Ag18Cl(Te3W38O134)2]n, where n=1 and m=0 for compound 1 (after 4 days), n=2 and m=3 for compound 2 (after 10 days), and n=∞ and m=5 for compound 3 (after 14 days). The reaction is based upon the self‐organization of two {Te3W38} units around a single chloride template and the formation of a {Ag12} cluster, giving a {Ag12}‐in‐{W76} cluster‐in‐cluster in compound 1 , which further aggregates to cluster compounds 2 and 3 by supramolecular Ag‐POM interactions. The proposed mechanism for the formation of the clusters has been studied by ESI‐MS. Further, control experiments demonstrate the crucial role that TeO32?, Cl?, and Ag+ play in the self‐assembly of compounds 1 – 3 . 相似文献
69.
Perturbation of Spin Crossover Behavior by Covalent Post‐Synthetic Modification of a Porous Metal–Organic Framework 下载免费PDF全文
John E. Clements Dr. Jason R. Price Dr. Suzanne M. Neville Prof. Cameron J. Kepert 《Angewandte Chemie (International ed. in English)》2014,53(38):10164-10168
Covalent post‐synthetic modification is a versatile method for gaining high‐level synthetic control over functionality within porous metal–organic frameworks and for generating new materials not accessible through one‐step framework syntheses. Here we apply this topotactic synthetic approach to a porous spin crossover framework and show through detailed comparison of the structures and properties of the as‐synthesised and covalently modified phases that the modification reaction proceeds quantitatively by a thermally activated single‐crystal‐to‐single‐crystal transformation to yield a material with lowered spin‐switching temperature, decreased lattice cooperativity, and altered color. Structure–function relationships to emerge from this comparison show that the approach provides a new route for tuning spin crossover through control over both outer‐sphere and steric interactions. 相似文献
70.
Kaitlyn A. Perez Cameron R. Rogers Emily A. Weiss 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(33):14195-14199
This Communication describes the use of CuInS2/ZnS quantum dots (QDs) as photocatalysts for the reductive deprotection of aryl sulfonyl-protected phenols. For a series of aryl sulfonates with electron-withdrawing substituents, the rate of deprotection for the corresponding phenyl aryl sulfonates increases with decreasing electrochemical potential for the two electron transfers within the catalytic cycle. The rate of deprotection for a substrate that contains a carboxylic acid, a known QD-binding group, is accelerated by more than a factor of ten from that expected from the electrochemical potential for the transformation, a result that suggests that formation of metastable electron donor–acceptor complexes provides a significant kinetic advantage. This deprotection method does not perturb the common NHBoc or toluenesulfonyl protecting groups and, as demonstrated with an estrone substrate, does not perturb proximate ketones, which are generally vulnerable to many chemical reduction methods used for this class of reactions. 相似文献