17332-11-5Relevant articles and documents
Discovery of Unforeseen Energy-Transfer-Based Transformations Using a Combined Screening Approach
Strieth-Kalthoff,Henkel, Christian,Teders, Michael,Kahnt, Axel,Knolle, Wolfgang,Gómez-Suárez, Adrián,Dirian, Konstantin,Alex, Wiebke,Bergander,Daniliuc, Constantin G.,Abel,Guldi, Dirk M.,Glorius
, p. 2183 - 2194 (2019)
The discovery of novel (catalytic) transformations and mechanisms is commonly based on rational design. However, many discoveries have resulted directly from experimental serendipity. Building on this, we report a two-dimensional screening protocol, combining “mechanism-based” and “reaction-based” screening and its application to the field of visible light photocatalysis. To this end, two energy-transfer-based cycloaddition reactions could be realized: a notably endergonic energy transfer process allows for the dearomative cycloaddition of benzothiophenes and related heterocycles. Moreover, by sensitization of enone moieties, a [2+2]-cycloaddition to alkynes and an unexpected cycloaddition-rearrangement cascade were discovered. Advanced spectroscopic techniques (in particular transient absorption spectroscopy and pulse radiolysis) were utilized to investigate the underlying photophysical processes and gain insight into reaction kinetics. Combining these results with further mechanistic analysis can eventually turn out to be helpful upon knowledge-driven development of improved systems. Such screening approaches can thus provide complementary access toward novel and more efficient catalytic protocols. Driven by the continuous demand for more efficient and sustainable synthetic reactions, the discovery of novel (catalytic) reactivity patterns remains a major challenge of synthetic chemistry. The discovery of such processes is commonly based on rational design, i.e., the expansion of previously acquired knowledge to new substrate classes or reaction types. However, considering that many groundbreaking discoveries have resulted from experimental serendipity, serendipity-based screening methodologies have been developed as a complementary tool for the discovery of novel transformations. Particularly in the context of visible-light-mediated photocatalysis, which provides a powerful platform from which to develop new radical-based transformations, screening methodologies still have significant potential to discover new reactivity modes. How can catalytic reactions be discovered? Here, a two-dimensional screening strategy for reaction discovery is described. For this purpose, the investigation of single mechanistic steps is merged with combinatorial screening. As a showcase, application to the field of visible light photocatalysis allowed for the discovery of three unexpected cyclization reactions. Extensive mechanistic analysis by advanced spectroscopic and computational tools enabled insights into the underlying molecular processes. In particular, a significantly endergonic sensitization event could be discovered and substantiated by transient absorption spectroscopy.
Multicomponent Coupling Approach to (±)-Frondosin B and a Ring-Expanded Analogue
Kerr, Daniel J.,Willis, Anthony C.,Flynn, Bernard L.
, p. 457 - 460 (2004)
(Equation presented) A recently discovered multicomponent coupling reaction is used to give direct access to a late intermediate in the synthesis of frondosin B. This intermediate can also be efficiently converted to a ring-expanded analogue of frondosin
Synthetic Studies toward Actinorhodin and γ-Actinorhodin by using a Homo-coupling Strategy: Synthesis of Hemiactinorhodin and Hemi-γ-actinorhodin
Mulay, Sandip V.,Bhowmik, Amit,Fernandes, Rodney A.
, p. 4931 - 4938 (2015)
A homo-coupling strategy toward the synthesis of actinorhodin and γ-actinorhodin has been explored. The monomeric unit was synthesized by employing an efficient combination of D?tz benzannulation and oxa-Pictet-Spengler reactions. Attempts towards oxidative homo-coupling of the pyranonaphthalene monomer intermediate to give dimer were unsuccessful. Later, monomer pyranonaphthalene was carried forward to complete the synthesis of hemiactinorhodin and hemi-γ-actinorhodin.
Iron- or Palladium-Catalyzed Reaction Cascades Merging Cycloisomerization and Cross-Coupling Chemistry
Gomes, Filipe,Echeverria, Pierre-Georges,Fürstner, Alois
, p. 16814 - 16822 (2018)
A conceptually novel reaction cascade is presented, which allows readily available enynes to be converted into functionalized 1,3-dienes comprising a stereodefined tetrasubstituted alkene unit; such compounds are difficult to make by conventional means. The overall transformation is thought to commence with formation of a metallacyclic intermediate that evolves via cleavage of an unstrained C?X bond in its backbone. This non-canonical cycloisomerization process is followed by a cross-coupling step, such that reductive C?C bond formation regenerates the necessary low-valent metal fragment and hence closes an intricate catalytic cycle. The cascade entails the formation of two new C?C bonds at the expense of the constitutional C?X entity of the substrate: importantly, the extruded group X must not be a heteroelement (X=O, NR), since activated β-C?C bonds can also be broken. This concern was reduced to practice in two largely complementary formats: one procedure relies on the use of alkyl-Grignard reagents in combination with catalytic amounts of Fe(acac)3, whereas the second method amalgamates cycloisomerization with Suzuki coupling by recourse to arylboronic acids and phosphine-ligated palladium catalysts.
o-Bromo-p-methoxyphenyl ethers. Protecting/radical translocating (PRT) groups that generate radicals from C-H bonds β to oxygen atoms
Curran, Dennis P.,Xu, Jinyou
, p. 3142 - 3147 (1996)
The o-bromo-p-methoxyphenyl ether group is introduced as a new protecting/radical translocating (PRT) group. This group protects an alcohol both before and after its use as a translocating group to generate a radical from a C-H bond β to the protected alc
A Conformationally Stable Contorted Hexabenzoovalene
Baumg?rtner, Kevin,Meza Chincha, Ana Lucia,Dreuw, Andreas,Rominger, Frank,Mastalerz, Michael
, p. 15594 - 15598 (2016)
Contorted two-dimensional aromatic molecules are fascinating synthetic targets because they are molecular “cutouts” of nonplanar graphene structures, fullerenes, or carbon nanotubes. In most cases, the curvature is introduced by the implementation of eith
Synthesis of novel tetracycles via an intramolecular Heck reaction with anti-hydride elimination
Lautens, Mark,Fang, Yuan-Qing
, p. 3679 - 3682 (2003)
(Matrix presented) The catalytic combination of Pd2(dba) 3/HP(t-Bu)3·BF4 and DABCO gives an unusual intramolecular Heck reaction with dihydronaphthalene substrates, yielding formal anti-hydride elimination produ
Synthetic method 4 - alkoxyphenol compounds
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Paragraph 0094-0096, (2021/09/29)
The invention discloses a synthetic method of 4 - alkoxyphenol compounds, and belongs to the field of organic chemical synthesis. The method is as follows: An aryl alkyl ether compound is added to the sealing tube. The catalyst dimerization acetic acid rhodium and the oxidizing agent iodobenzene diethyl ester are added, a solvent trifluoroacetic anhydride is added, and the 4 -alkoxyphenol compound is prepared by heating reaction. To the invention, high regioselectivity direct hydroxylation of the aryl alkyl ether compound is realized, the application range of the substrate is wide, the yield is high, the activity after amplification reaction does not significantly decay, and higher yield is still obtained. The utility model has good practicability and industrial application prospect.
Para -Selective hydroxylation of alkyl aryl ethers
Zhu, Runqing,Sun, Qianqian,Li, Jing,Li, Luohao,Gao, Qinghe,Wang, Yakun,Fang, Lizhen
supporting information, p. 13190 - 13193 (2021/12/16)
para-Selective hydroxylation of alkyl aryl ethers is established, which proceeds with a ruthenium(ii) catalyst, hypervalent iodine(iii) and trifluoroacetic anhydride via a radical mechanism. This protocol tolerates a wide scope of substrates and provides a facile and efficient method for preparing clinical drugs monobenzone and pramocaine on a gram scale.
Coumarins by Direct Annulation: β-Borylacrylates as Ambiphilic C3-Synthons
Wienhold, Max,Molloy, John J.,Daniliuc, Constantin G.,Gilmour, Ryan
supporting information, p. 685 - 689 (2020/11/30)
Modular β-borylacrylates have been validated as programmable, ambiphilic C3-synthons in the cascade annulation of 2-halo-phenol derivatives to generate structurally and electronically diverse coumarins. Key to this [3+3] disconnection is the BPin unit which serves a dual purpose as both a traceless linker for C(sp2)–C(sp2) coupling, and as a chromophore extension to enable inversion of the alkene geometry via selective energy transfer catalysis. Mild isomerisation is a pre-condition to access 3-substituted coumarins and provides a handle for divergence. The method is showcased in the synthesis of representative natural products that contain this venerable chemotype. Facile entry into π-expanded estrone derivatives modified at the A-ring is disclosed to demonstrate the potential of the method in bioassay development or in drug repurposing.
