Answer to Question #94195 in Mechanics | Relativity for Mereoni

Question

Acid-catalyzed cascade reactions are employed by nature and also by synthetic chemists in the construction of complex polycyclic molecules, including steroids. Provide a mechanism for the following multiple cyclization.

Answer 1

Complex polycyclic molecules are used as biological tools and drug candidates for clinical development. In this way, synthetic organic chemists have the power to replicate some of the most intriguing molecules of living nature in the laboratory and apply their developed synthetic strategies and technologies to construct variations of them. A cascade (or tandem) reaction is an intramolecular reaction that allows the organic synthesis of fairly complex multinuclear organic molecules from just one precursor (non-cyclic).

The efficient, stereocontrolled construction of polycyclic ring systems has long presented a formidable challenge to synthetic chemists. Cascade reactions offer a ‘quick fix’—building multiple rings in a single step—and often dramatically shorten a synthetic route. In general, these reactions can include many stages, which, for the most part, are spontaneous and uncontrolled. Depending on the initial product subjected to the acidic cascade synthetic process, a general reaction mechanism can be seen. For this, it is necessary to know the initial product subjected to the reactions, as well as the catalyst. For example, the use of BF₃ as a catalyst can affect the “opening” of epoxy rings.