Regioselective allenylation and propargylation of various para-quinone methides using alkynyl azaarenes as pronucleophiles.

We have developed Brønsted base-mediated regioselective allenylation and propargylation of various para-quinone methides using unfunctionalized 2-alkynyl azaarenes as pronucleophiles. The appropriate choice of a base provides an opportunity to achieve either an allenylated product or the propargylated product. The use of KOtBu as a Brønsted base promotes the formation of allenylated products, whereas NaN(SiMe3)2 furnishes the propargylated products. Besides, the current strategy is scalable and can be performed on a gram scale.

Base-promoted 1,6-conjugate addition of alkylazaarenes to para-quinone methides.

1,1,2-Triarylethanes embedded with an azaarene unit were prepared in a single step at ambient temperature via the sodium hexamethyldisilazide mediated 1,6-conjugate addition of unactivated alkylazaarenes on para-quinone methides (p-QMs). The extent of this methodology was investigated with a wide range of p-QMs and alkylazaarenes, and the respective products were obtained in moderate to excellent yields. The regioselective 1,6-conjugate addition of the trialkylazaarene precursor on para-quinone methide was also presented. Besides, we showcased the direct synthesis of the 1,1,2-triarylethane derivative from aldehyde via the in situ generation of para-quinone methide.