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.
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.
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
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
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.
Regioselective monobromination of phenols with KBr and ZnAl–BrO3?–layered double hydroxides
Wang, Ligeng,Feng, Chun,Zhang, Yan,Hu, Jun
supporting information, (2020/02/22)
The regioselective mono-bromination of phenols has been successfully developed with KBr and ZnAl–BrO3?–layered double hydroxides (abbreviated as ZnAl–BrO3?–LDHs) as brominating reagents. The para site is much favorable and the ortho site takes the priority if para site is occupied. This reaction featured with excellent regioselectivity, cheap brominating reagents, mild reaction condition, high atom economy, broad substrate scope, and provided an efficient method to synthesize bromophenols.