Synthesis of Spiro[5.5]trienones- and Spiro[4.5]trienones-Fused Selenocyanates via Electrophilic Selenocyanogen Cyclization and Dearomative Spirocyclization

Abstract

A practical strategy for the synthesis of spiro[5.5]­trienones-fused selenocyanates and spiro[4.5]­trienones-fused selenocyanates through electrophilic selenocyanogen cyclization and dearomative spirocyclization is reported. This approach was conducted under mild conditions with broad substrate scope and good functional group tolerance. The utility of this procedure is exhibited in the late-stage functionalization of nature product and drug molecules.

Photoredox‐Catalyzed Thiocyanative Cyclization of Biaryl Ynones to Thiocyanated Spiro[5.5]trienones: An External‐Oxidant‐ and Transition‐Metal‐Free Approach

“…After the development of the first‐ever spiro[5.5]trienones or dibenzocycloheptene‐5‐ones by Chen and co‐workers through the intramolecular electrophilic cyclization of biaryl ynones [16] . The groups of Xia, [17] Chen, [18] Wang, [19] Zhang, [14a] and Duan [13e] independently reported the transition ‐metal catalyzed dearomatizations of biaryl ynones to spiro[5.5]trienones. Although each of these approaches efficiently yields spiro[5.5]trienones with various substituents, doing so entails the use of costly metal catalysts and/or exterior oxidants, which in turn confine the compatibility of the functional groups and result in the production of toxic byproducts.…”

Visible Light Promoted Brominative Dearomatization of Biaryl Ynones to Spirocycles

“…In this context, Chen and co-workers first developed spiro[5.5]­trienones or dibenzocycloheptene-5-ones via ICl-induced intramolecular electrophilic iodo-cyclization of biaryl ynones . In this study, it was shown that depending on the substituent effects on the distal phenyl group of the substrate, a mixture of 6- endo -dig and/or 7- endo -dig cyclization products was formed.…”