One-Pot Regioselective Synthesis
of <i>meta</i>-Terphenyls via [3 + 3] Annulation of Nitroallylic
Acetates with
Alkylidenemalononitriles
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Abstract
A highly
efficient one-pot method has been developed for the synthesis
of <i>meta</i>-terphenyls via a regioselective [3 + 3] annulation-elimination
sequence involving Morita–Baylis–Hillman (MBH) acetates
of nitroalkenes and alkylidenemalononitriles. The reaction takes place
in a regioselective manner under mild conditions (Et<sub>3</sub>N,
room temperature) to afford a wide variety of <i>meta</i>-terphenyls bearing aryl, heteroaryl and styrenyl groups. This novel
[3 + 3] annulation takes advantage of the 1,3-bielectrophilic character
of MBH acetates and 1,3-binucleophilic character of alkylidenemalononitriles
and proceeds in a cascade fashion comprising an S<sub>N</sub>2′
substitution, intramolecular 6-<i>endo-trig</i> Michael
addition and double elimination. Representative synthetic transformations
of the products, for instance, to <i>meta</i>-terphenyl
derived isoindolinones have also been demonstrated
