Transition metal-free [3 + 3] annulation of cyclopropanols with ß-enamine esters to assemble nicotinate derivatives.

A metal-free and efficient approach for the synthesis of structurally important nicotinates through 4-HO-TEMPO-mediated [3 + 3] annulation of cyclopropanols with ß-enamine esters is presented. This protocol features high atom efficiency, green waste, simple operation and broad substrate scope. Moreover, the experiments of gram-scale synthesis and recovery of oxidants make this strategy more sustainable and practical.

Copper-catalyzed 4-HO-TEMPOH mediated phosphorylation of alkenes.

An efficient, practical and regioselective synthesis of (E)-alkenylphosphine oxides has been developed starting from alkenes under copper catalysis and 4-HO-TEMPOH oxidation. Preliminary mechanistic studies clearly reveal that a phosphinoyl radical is involved in this process. Moreover, this method features mild reaction conditions, good functional group tolerance, and excellent regioselectivity and also promises to be efficient for the late-stage functionalization of drug molecular skeletons. The reaction will create an opportunity for the synthesis of complex phosphorus containing bioactive molecules.

Iron-catalyzed regioselective synthesis of (E)-vinyl sulfones mediated by unprotected hydroxylamines.

An Fe-catalyzed unprotected hydroxylamine mediated Heck-type coupling between sulfinic acids and alkenes for the regioselective synthesis of (E)-vinyl sulfones has been developed. Mechanism studies indicated for the first time that a radical process may be involved and that hydroxylamines play multiple roles, including those of a mild oxidant and an in situ base. It was found for the first time that this transformation not only realizes C-S bond construction promoted by unprotected hydroxylamines, but also provides a practical and complementary method for the preparation of structurally important (E)-vinyl sulfones.

Cu-Catalyzed [3 + 3] Annulation for the Synthesis of Pyrimidines via ß-C(sp3)-H Functionalization of Saturated Ketones.

A novel, efficient, and facile approach for the synthesis of structurally important pyrimidines has been successfully developed by Cu-catalyzed and 4-HO-TEMPO-mediated [3 + 3] annulation of commercially available amidines with saturated ketones. This method provides a new protocol for the synthesis of pyrimidines by a cascade reaction of oxidative dehydrogenation/annulation/oxidative aromatization via direct ß-C(sp3)-H functionalization of saturated ketones followed by annulation with amidines.