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The Diels-Alder reaction is perhaps the most important and commonly taught cycloaddition reaction. Formally it is a [4+2] cycloaddition reaction and exists in a huge range of forms, including the inverse electron-demand Diels–Alder reaction, hexadehydro Diels–Alder reaction and the related alkyne trimerisation.
The azide-alkyne Huisgen cycloaddition is a 1,3-dipolar cycloaddition between an azide and a terminal or internal alkyne to give a 1,2,3-triazole. Rolf Huisgen [1] was the first to understand the scope of this organic reaction.
The [4+4] Photocycloaddition is a cycloaddition reaction in which two unsaturated molecules connect via four atoms from each molecule (hence "4 + 4") to create an eight-membered ring. As a photochemical reaction, it is promoted by some form of light, as opposed to a thermal process.
The 1,3-dipolar cycloaddition is a chemical reaction between a 1,3-dipole and a dipolarophile to form a five-membered ring. The earliest 1,3-dipolar cycloadditions were described in the late 19th century to the early 20th century, following the discovery of 1,3-dipoles.
The periselectivity of a particular reaction depends on the structure of both the ketene and the substrate. Although the reaction is predominantly used to form four-membered rings, a limited number of substrates undergo [3+2] or [4+2] reactions with ketenes. Examples of all three modes of cycloaddition are discussed in this section.
The nitrone-olefin (3+2) cycloaddition reaction is the combination of a nitrone with an alkene or alkyne to generate an isoxazoline or isoxazolidine via a (3+2) cycloaddition process. [1] This reaction is a 1,3-dipolar cycloaddition, in which the nitrone acts as the 1,3-dipole, and the alkene or alkyne as the dipolarophile.
In organic chemistry, enone–alkene cycloadditions are a version of the [2+2] cycloaddition. This reaction involves an enone and alkene as substrates. Although the concerted photochemical [2+2] cycloaddition is allowed, the reaction between enones and alkenes is stepwise and involves discrete diradical intermediates. [1]
The Aza-Diels–Alder reaction is a modification of the Diels–Alder reaction wherein a nitrogen replaces sp 2 carbon. [1] ... [4+2] cycloaddition with imines. Regio ...