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It was demonstrated that ortho-substituted anilines are prone to undergo hydroamination reactions with diethyl acetylenedicarboxylate in a planetary ball mill. A sequential coupling of the intermolecular hydroamination reaction with intramolecular ring closure was utilized for the syntheses of benzooxazines, quinoxalines, and benzothiazines from readily available building blocks, that is, electrophilic alkynes and anilines with OH, NH, or SH groups in the ortho position. For the heterocycle formation, it was shown that several stress conditions were able to initiate the reaction in the solid state. Processing in a ball mill seemed to be advantageous over comminution with mortar and pestle with respect to process control. In the latter case, significant postreaction modification occurred during solid-state analysis. Cryogenic milling proved to have an adverse effect on the molecular transformation of the reagents.

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Ortho-substituted anilines (I) undergo hydroamination reactions with diethyl acetylenedicarboxylate in a planetary ball mill. A sequential coupling of the intermolecular hydroamination reaction with intramolecular ring closure is utilized for the syntheses of benzoxazines, quinoxalines, and benzothiazines using a mixer ball mill. For the reaction with alkyne (VIII), addition of PPh 3 is required providing the first example for such a synthesis under solvent-free conditions with a ball mill. -(WEISSE, M.; ZILLE, M.; JACOB, K.; SCHMIDT, R.; STOLLE*, A.; Chem. -Eur. J. 21 (2015) 17, 6511-6522, http://dx.