A cascade cyclization is a chemical transformation in which two or more consecutive reactions take place, such that the latter occurs as a result of functionality formed in the former. Cationic cyclizations of terpenoids and meroterpenoids have been known for some time, and frequently are terminated by cationic addition to an olefin or arene. Recently we have discovered that termination of a cationic cascade by reaction with a methoxymethyl (MOM) protected phenol can result not only in the classical cyclization but also that the MOM cation liberated can participate in an electrophilic aromatic substitution that appears to be regiospecific. This strategy has been utilized successfully in the syntheses of schweinfurthin A and angelichalcone. New applications of this tandem reaction sequence in compounds such as the symmetric epoxide 1 have been used to prepare the benzopyran 2. Elaboration of compound 2 to natural products such as Xanthoangelol H (3) is currently under investigation, and the results of these studies will be presented.

Termination of cascade cyclizations by MOM-protected phenols

253rd National Meeting (2017)

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