Domino reactions Diels- Alder/Schmidt

Partially hydrogenated indoles are useful heterocycles. They can easily be obtained by a domino Diels-Alder/Schmidt process, as described by Aube and coworkers [30]. An example is the reaction of the enone 4-90 with a butadiene 4-91 in the presence of the Lewis acid MeAlCl2, which led to tricyclic compounds as 4-93 via 4-92 in over 80% yield (Scheme 4.20). The procedure has also been used for the synthesis of pyrroloisoquinolones, azepinoindolones, and perhydroindoles. 

Quite recently, a domino Diels-Alder/Prins/pinacol reaction was reported by Barriaulfs group [38]. This novel method is very reliable and efficient for the synthesis of highly functionalized bicyclo[m.n.l]alkanones. In addition, Aube and coworker [39] used a combination of a Diels-Alder and a Schmidt reaction within the total synthesis of the Stemona alkaloid stenine [40]. 

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