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Generation of the benzyne intermediate is the slow step in the reaction. [20] "Aryne coupling" reactions allow for generation of biphenyl compounds which are valuable in pharmaceutical industry, agriculture and as ligands in many metal-catalyzed transformations. [21]
The benzyne serves as the enophile, while the ene can be an alkene (Alder ene) or an aromatic ring (aromatic ene). Lee and co-workers have shown an HDDA-Alder ene cascade reaction that can produce a variety of products, including medium-sized fused rings, spirocycles , and allenes .
The next member is [6]annulyne or benzyne which is a reactive intermediate well known in organic chemistry. [8]annulyne is known to exist but quickly dimerizes or trimerizes; the compound has been trapped as its radical anion and observed by EPR spectroscopy. [10]annulyne, like [4]annulyne, only exists in theory. [1]
In the hexadehydro Diels–Alder reaction, alkynes and diynes are used instead of alkenes and dienes, forming an unstable benzyne intermediate which can then be trapped to form an aromatic product. This reaction allows the formation of heavily functionalized aromatic rings in a single step. [58] [59]
The biphenylene structure can also be understood as a dimer of the reactive intermediate benzyne, which in fact serves as a major synthetic route, by heating the benzenediazonium-2-carboxylate zwitterion prepared from 2-aminobenzoic acid. [13] Another approach is by N-amination of 1H-benzotriazole with hydroxylamine-O-sulfonic acid.
Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group is replaced by a heteroatom: oxygen, nitrogen, or sulfur. [3] Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one ...
A nucleophilic aromatic substitution (S N Ar) is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring. Aromatic rings are usually nucleophilic, but some aromatic compounds do undergo nucleophilic substitution.
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation. When their existence is ...