Unprecedented “off-pathway” [2+2] cycloaddition-retroelectrocyclization reaction between an unsymmetric alkyne and tetracyanoquinodimethane [supplementary raw data]

Besides its simplicity, fast rate, and high yield, this reaction may also display complete and predictable regioselectivity, as in the case when tetracyanoquinodimethane (TCNQ) is used in combination with unsymmetric, activated alkynes.

Here, we report the first example of a [2+2] CA-RE reaction between TCNQ and an aniline-activated alkyne following an “inverted” regiochemistry, thus leading to the exclusive formation of an unexpected regioisomer in contrast to the expected one. A combined experimental and theoretical study helped us to unravel the peculiar reaction mechanism underlying the regioselectivity switching. Characterization of compounds (Raw data).