Hydrogen Bond Donor-Catalyzed\nOne-Pot Transformations\nof 2,2-Disubstituted Epoxides: Synthesis of Functionalized Nitrile-Rich\nDerivatives

A practically\nintriguing catalytic domino methodology\nhas been\ndeveloped for the synthesis of highly functionalized pyran and ethene-1,1,2-tricarbonitrile\nderivatives in a single-pot operation. The <i>gem</i>-dicyano\nolefins and the corresponding epoxide were taken as the reactive partners\nin the presence of a hydrogen bond donor (HBD)-catalyzed condition.\nThe reaction was found to be highly efficient in terms of the formation\nof sequential C–C and O–C bonds along with an exceptional\nC<sub>Sp</sub><sup>2</sup>–C<sub>Sp</sub> coupling step through\na metal-free organocatalytic pathway. This strategy has been further\nutilized on ester-substituted epoxides, although the results differ\nfrom those with <i>gem</i>-dicyano epoxides. The process\nremains versatile and effective across a wide range of substrates.\nThis catalytic protocol has been proven to be very generalized with\nvarieties of substrate scope. A low catalyst loading, ambient reaction\nconditions, and satisfactory yields of all of the products are the\nvital features of this approach. Moreover, the overall atom-economic\noutcome along with the synergistic reactivity pattern between the\nactivated epoxide and the malononitrile derivatives is also very significant\nto address the originality of this process. Spectroscopic analysis\nis utilized to validate the mechanistic interpretation.