Small-molecule compounds 3+2 cycloaddition synthesis

The Diels-Alder cycloaddition is the best-known organic reaction that is widely used to construct, in a regio- and stereo-controlled way, a six-membered ring with up to four stereogenic centers. With the potential of forming carbon-carbon, carbon-heteroatom and heteroatom-heteroatom bonds, the reaction is a versatile synthetic tool for constructing simple and complex molecules [1], Scheme 1.1 illustrates two examples the synthesis of a small molecule such as the tricyclic compound 1 by intermolecular Diels-Alder reaction [2] and the construction of a complex compound, like 2, which is the key intermediate in the synthesis of (-)chlorothricolide 3, by a combination of an intermolecular and an intramolecular Diels-Alder cycloaddition [3]. 

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