762-21-0Relevant articles and documents
Generating carbyne equivalents with photoredox catalysis
Wang, Zhaofeng,Herraiz, Ana G.,Del Hoyo, Ana M.,Suero, Marcos G.
, p. 86 - 91 (2018/02/09)
Carbon has the unique ability to bind four atoms and form stable tetravalent structures that are prevalent in nature. The lack of one or two valences leads to a set of species - carbocations, carbanions, radicals and carbenes - that is fundamental to our understanding of chemical reactivity. In contrast, the carbyne - a monovalent carbon with three non-bonded electrons - is a relatively unexplored reactive intermediate; the design of reactions involving a carbyne is limited by challenges associated with controlling its extreme reactivity and the lack of efficient sources. Given the innate ability of carbynes to form three new covalent bonds sequentially, we anticipated that a catalytic method of generating carbynes or related stabilized species would allow what we term an € assembly point' disconnection approach for the construction of chiral centres. Here we describe a catalytic strategy that generates diazomethyl radicals as direct equivalents of carbyne species using visible-light photoredox catalysis. The ability of these carbyne equivalents to induce site-selective carbon-hydrogen bond cleavage in aromatic rings enables a useful diazomethylation reaction, which underpins sequencing control for the late-stage assembly-point functionalization of medically relevant agents. Our strategy provides an efficient route to libraries of potentially bioactive molecules through the installation of tailored chiral centres at carbon-hydrogen bonds, while complementing current translational late-stage functionalization processes. Furthermore, we exploit the dual radical and carbene character of the generated carbyne equivalent in the direct transformation of abundant chemical feedstocks into valuable chiral molecules.
Propeller-Shaped D3h-Symmetric Macrocycles with Three 1,8-Diazaanthracene Blades as Building Blocks for Photochemically Induced Growth Reactions
Servalli, Marco,Gyr, Luzia,Sakamoto, Junji,Schlüter, A. Dieter
supporting information, p. 4519 - 4523 (2015/07/27)
The efficient synthesis of new D3h-symmetric propeller-shaped, double-decker compounds with three vertically standing diazaanthracene units arranged so as to allow for photochemically induced intermolecular growth reaction by [4+4] cycloaddition is presented. The propellers bear alkyl chains of four different lengths (ethyl, propyl, hexyl, dodecyl) to have flexibility in creating ordered arrays by packing them into single crystals, onto solid substrates or into mesophases. All propellers are obtained in only six steps and on a 50-200 mg scale. The sequence passes through the ditriflated 1,8-diazaanthracene derivatives 6 which are a very versatile building block for many purposes and were therefore synthesized on a 30 g scale. A new class of propeller-shaped macrocycles is accessible via a six-step procedure with overall yields ranging from 6-16%. These cyclophanes are equipped with 1,8-diazaanthracene units and are designed for photochemical growth reactions in two dimensions.
N-heterocyclic carbenes of indazole: Ring enlargement reactions by α-halo ketones and dehalogenations of vicinal dihalides
Schmidt, Andreas,Snovydovych, Bohdan,Gjikaj, Mimoza
experimental part, p. 2798 - 2804 (2009/04/05)
On decarboxylation, 1,2-dimethylindazolium-3-carboxylate forms the N-heterocyclic carbene, 1,2-dimethylindazol-3-ylidene, which deprotonates α-halo ketones. The resulting indazolium salt and the corresponding enolate form 1:1 adducts which undergo a ring enlargement to cinnolines. Reaction with 2-bromo-2,3-dihydro-1H-inden-1-one gives a 4- hydroxyspiro[cinnoline-3,2′-inden]-1′-one by ring enlargement reaction (X-ray crystal structure analysis). Vicinal dibromides undergo debromination under these conditions to give alkenes, and substrates with 1,2-dibromoethene partial structure give acetylenes. As 3-bromoindazole is found as the second product of this reaction, an E1cb mechanism, initiated by Br+ abstraction by the N-heterocyclic carbene of indazole, is suggested. Georg Thieme Verlag Stuttgart.
