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July 2016
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25 Reads
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19 Citations
The Journal of Organic Chemistry
A formal total synthesis of ivorenolide A has been accomplished employing a Z-selective olefin cross metathesis and a macrocyclic Glaser-Hay coupling as key steps. The macrocyclization protocol employed a phase separation/continuous flow manifold whose advantages include catalysis, fast reaction times, high concentrations and facile scale-up.
September 2015
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15 Reads
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46 Citations
An evaluation of both a visible-light- and UV-light-mediated synthesis of carbazoles from various triarylamines with differing electronic properties under continuous-flow conditions has been conducted. In general, triarylamines bearing electron-rich groups tend to produce higher yields than triarylamines possessing electron-withdrawing groups. The incorporation of nitrogen-based heterocycles, as well as halogen-containing arenes in carbazole skeletons, was well tolerated, and often synthetically useful complementarity was observed between the UV-light and visible-light (photoredox) methods.
September 2015
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39 Reads
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1 Citation
C8H7N (MW 129.16) InChI = 1/C9H7N/c1-2-6-9-8(4-1)5-3-7-10-9/h1-7H InChIKey = SMWDFEZZVXVKRB-UHFFFAOYAU (useful as a base, solvent and/or catalyst, especially for decarboxylation reactions1 and the Rosenmund reaction2, 3) Physical Data: mp −15 °C; bp 237.6 °C;4 steam volatile; d 1.0858 g cm−3 at 30 °C; pKa 9.5.5 Solubility: sol ethanol, ethyl ether, acetone, carbon disulfide; more readily sol hot water than cold water; quinoline dissolves sulfur, phosphorus, and arsenic trioxide. Form Supplied in: colorless liquid. Analysis of Reagent Purity: GLC. Purification: distillation. Handling, Storage, and Precautions: very hygroscopic; darkens on storage in light; package with protection from light and moisture; LD50 rat (oral) 460 mg kg−1; incompatible with strong oxidizing agents and strong acids.5, 6
September 2015
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8 Reads
September 2015
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140 Reads
C6H5N3 (MW 119.13) InChI = 1S/C6H5N3/c1-2-4-6-5(3-1)7-9-8-6/h1-4H,(H,7,8,9) InChIKey = QRUDEWIWKLJBPS-UHFFFAOYSA-N (building block, transition metal ligands) Alternate Names: BTA; 1,2,3-benzotriazole; 1H-benzotriazole; 1H-benzo[d][1,2,3]triazole; azimidobenzene; benzene azimide; benzisotriazole. Physical Data: mp 99–101 °C.1, 2 Solubility: soluble in water, alcohols, benzene, chloroform, dimethylformamide, and toluene. Form Supplied in: white or beige solid (widely available). Analysis of Reagent Purity: 1H NMR (CDCl3, 400 MHz): δ (ppm) 7.34–7.46 (m, 2H), 7.96 (s, 2H) 15.10 (s, 1H); 13C NMR (CDCl3, 100 MHz): δ (ppm) 138.1, 126.0, 114.8; ESI-MS (m/z): [M+H]+, 142.0 [M+Na]+; IR (KBr, film), νmax (cm−1): 3250, 3077, 2793, 2709, 1993, 1460, 1421, 1383, 1208, 1006, 877, 742.2 Purification: recrystallization from chloroform.1 Handling, Storage, and Precautions: avoid contact with skin and eyes. Avoid formation of dust and aerosols. Provide appropriate exhaust ventilation at places where dust is formed. Keep container tightly closed in a dry and well-ventilated place.
September 2015
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25 Reads
C2H3N3?(MW 69.0327) 1S/C2H3N3/c1-2-4-5-3-1/h1-2H,(H,3,4,5) InChIKey?=?QWENRTYMTSOGBR-UHFFFAOYSA-N (heterocycles, triazoles, material science, medicinal chemistry) Physical Data: bp: 203.0??C, d 1.274 g cm?3. Analysis of Reagent Purity: 1H NMR (300 MHz, CD2Cl2): ? 16.37 (s, 1H), 7.98 (s, 2H) ppm.13C {1H} NMR (125 MHz, DMSO-d6): ? 130.7 ppm.
May 2015
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16 Reads
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18 Citations
Chemical Communications
Efficient direct synthesis of macrodiolides via catalysis using Hf(OTf)4 is possible in high yields, forming water as the sole by-product. The first protocol for the direct synthesis of macrodiolides from equimolar mixtures of diols and dicarboxylic acids was developed (58-96 %). In addition, modification of the reaction concentration allows for the synthesis of head-to-tail macrodiolides from the corresponding seco acids. The catalytic preparation of the macrodiolides using a commercially available catalyst without the need for slow addition or azeotropic condition provides an operationally simple alternative to protocols which employ toxic tin catalysts or stoechiometric activation strategies
April 2015
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48 Reads
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8 Citations
Journal of Flow Chemistry
The continuous-flow synthesis of a series of 11- to 26-membered macrocycles via copper-catalyzed azide-alkyne cycloaddition is reported. The approach employs homogeneous catalysis to promote formation of triazole-containing macrocycles in good to excellent yields (65-90%) at relatively high concentration (30-50 mM) using a phase separation strategy.
March 2015
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82 Reads
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6 Citations
Solvent and additive effects can allow for the precise fine-tuning of an olefin metathesis reaction. Through choice of solvent, it is possible to augment initiation rates and the reactivity of catalysts to facilitate once-challenging transformations. Additives ranging from simple alcohols, ethylene and other olefins, halide salts, and Lewis-acids can all influence the outcome of olefin metathesis reactions.
February 2015
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61 Reads
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32 Citations
ACS Catalysis
Efficient direct macrolactonization of seco acids can be catalyzed by Hf(OTf)4 in high yields, forming water as the sole byproduct. The Hf(OTf)4 catalyst possesses unique reactivity characteristics relative to other Lewis acids, as it promotes macrolactonization over hydrolysis even in the presence of excess water. In addition to forming a variety of macrolactones and benzolactones (55-90%), intermolecular direct esterifications of carboxylic acids and alcohols were also possible and demonstrated compatibility with common carbamate, silyl ether, alkoxymethyl ether, and acetal protecting groups. All of the macrolactonization and esterification processes developed are operationally simple, “one-pot” reactions that exploit a commercially available catalyst without the need for slow addition or azeotropic techniques.Keywords: macrolactonization; hafnium; esterification; macrocyclization; Lewis acids; catalysis
... More recently, Collins extended the macrolactonization process to access cyclophanes bearing a chiral ansa chain by merging transition metal (TM) catalysis with biocatalysis ( Fig. 1D). 47 Although this strategy does not achieve planar-chiral control, the dual-catalysis protocol offers a potential solution to address the assembly of planar and central chiralities in a single step. ...
July 2024
Nature Synthesis
... A thiol-yne reaction of alkynyl sulfides and thiols was successfully developed using the nonmetal photocatalyst eosin Y under green LED irradiations and air atmosphere by Collins's group (Scheme 23). [28] This methodology facilitated the transformation of alkynyl sulfides with good yields, ranging from 42 % to 68 % across 11 examples, predominantly yielding cis isomers. Notably, no addition occurred at the α-position of alkynyl sulfides, with regioselectivity presumably governed by the stabilization of radical intermediates by the adjacent sulfur atom. ...
November 2023
The Journal of Organic Chemistry
... [19] Recently, a photo-enzymatic DKR of secondary alcohols employing Candida antarctica lipase B (CAL-B) and Cu(dtbbpy)(DPEPhos)BF 4 coupled with disulfide (Ph 3 SiS) 2 was reported, requiring a stoichiometric amount of 1,4-diazabicyclo[2.2.2]octane (DABCO), again in an organic solvent. [20] On the other hand, DKR strategies for acylating secalcohols employing enzymes for both the racemization and acylation steps have been reported scarcely and required organic phases due to the enzyme used for the acylation step. [21] In turn, alcohol dehydrogenases (ADHs) used for the racemization of sec-alcohols require an aqueous environment. ...
June 2023
ACS Catalysis
... 829 A series of heteroleptic diimine-Binap copper(I) complexes [Cu(NN)(PP 41 )]BF 4 with π-extended diimine ligands including dpq (bis(desmethyl) analogue of ddpq NN 195 ), dppz (NN 197 ) and bdppz (bis(desmethyl) analogue of NN 251 ) were synthesized and characterized. 830 They were shown to display acceptable levels of activity for the reductive debromination of an alkyl bromide but negligible activity in PCET or ET processes. The influence of the incorporation of a naphthalimide unit to the diimine ligand in [Cu(phen)-(Xantphos)]PF 6 ([Cu(NN 1 )(PP 4 )]PF 6 ) was reported and revealed the importance of the way this unit is incorporated (covalently linked or fused). ...
June 2022
... [15] As the large-scale synthesis of 2,3-D-A-norbornadienes through a Diels-Alder reaction in flow is established, [14] a current challenge is thus to develop efficient, scalable, and as sustainable as possible chemistry routes for the required dienophile precursors, such as propynenitriles. These valuable molecules can be prepared from their corresponding acetophenones, [16] derivatives that can also be obtained from bio-based renewable sources such as lignin, [17][18][19] thus comply-ing with principle 7 of the "Green ChemisTREE". [20] Alternative synthetic approaches towards propynenitriles include the introduction of the nitrile group in terminal acetylenes, [21][22][23][24] the conversion of other functional groups (e. g. ...
May 2022
Green Chemistry
... 16,32,72 On the other hand, the photocatalytic isomerization of (E)-to (Z)stilbene was selected as second model reaction. 13,30,73 In all photocatalytic measurements, light > 400 nm was used to prove that visible light is sufficient to enable the efficient use of Al(III) PSs. ...
July 2021
ACS Catalysis
... Vor diesem Hintergrund ist es wichtig, Flow Chemistry auch in die Lehre zu integrieren (Blanco-Ania & Rutjes, 2017). Im Sinne der curricularen Innovationsforschung soll sich Lehre mit aktuellen, relevanten Forschungsthemen und -erkenntnissen mitentwickeln (Tausch, 2004), um die Fähigkeiten der Studierenden im Hinblick auf ihre berufliche Zukunft als Chemiker:innen zu fördern (Kairouz, Charette & Collins, 2021). So empfehlen Blanco-Ania & Rutjes (2017) die Implementierung von Flow Chemistry-Elementen an Hochschulen bereits im frühen Stadium des Bachelorstudiums, da hier Studierende ihre ersten Laborpraktika absolvieren und Elemente der Flow Chemistry bereits an dieser Stelle in die Lehre eingebettet werden sollten. ...
January 2021
Journal of Flow Chemistry
... [46] However, the efficient preparation of SeMCs remains a severe challenge because of the limited selenylation methods, [47] especially for the underexplored selenylalkyne containing macrocycles because the intramolecular C(sp)-Se bond formation reaction suitable for constructing macrocycles has not been reported yet. Generally, the synthesis of selenylalkyne containing macrocycles is more challenging than ordinary macrocyclization as there are four consecutive atoms (SeÀ C�CÀ C) arranged in a linear geometry [48] (verified by the crystal structure of SeMC-13, Figure 3), which resulted in stronger ring tension and higher entropic penalty [49] involved in the ring-closing process. Encouraged by the excellent performance of this SeNEx chemistry in intermolecular reactions, we next tested the feasibility of this reaction in SeMCs synthesis. ...
October 2020
... In 2020, Collins reported a general Cu-catalyzed cross-coupling between bromoalkynes and thiols to construct C(sp)À S bond. [38] After examining the reaction carefully, the optimized conditions were obtained as following: a mixture of bromoalkynes 2 (0.24 mmol), thiols 1 (0.26 mmol), Cu(MeCN) 4 PF 6 (0.024 mmol), dtbbpy (0.048 mmol) and 2,6-lutidine (0.48 mmol) in MeCN at rt for 10 min. This Cu-catalyzed cross-coupling was highly tolerant with a wide scope of functionalities. ...
July 2020
Organic Letters
... On the other hand, organosulfur compounds have long been considered a poison for several transition metal catalysts, which may also have contributed to slowing the adoption of these compounds especially in the field of organometallic synthetic chemistry. However, in recent years, due to the growing interest in sulfur-containing molecules in the pharmaceutical or materials chemistry fields, [2] the chemistry of alkynyl sulfides has shown significant progress, whether for their synthesis [3] or for their applications. [4] They were used in particular as substrates of choice for various mono or difunctionalization reactions such as carbo-or hydrometallation, [5] or hydroelementation, [6] giving access stereo and regioselectively to functionalized tri-or tetrasubstituted alkenyl sulfides. ...
June 2020
Organic & Biomolecular Chemistry
