Schmidt reactions domino

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]. 

Domino reactions, which combine sequential transformations in a single pot, can allow the rapid development of complex products from simple starting materials. One design feature required for successful domino process involves control over the order of reaction events. Since Bronsted acids or Lewis acids are required for the initiation of nearly all azido-Schmidt reactions, combining such reactions with other acid-accelerated processes presents a logical starting point for assembling Schmidt-centric tandem reactions. 

Scheme 7.34 Domino Dieis-Aider/Schmidt reactions...

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. 

A one-pot domino Claisen-Schmidt/l,3-dipolar cycloaddition/oxidation reaction sequence involving an aldehyde (801), a methyl ketone (802), and the Bestmann Ohira reagent (803), has been developed for the synthesis of variously substituted 3-carbo-5-phosphonylpyrazoles (804) (Scheme 204). ... 

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