Morpholinone- and piperidinone-derived triazolium salts are shown to catalyze highly chemoselective cross-benzoin reactions between aliphatic and aromatic aldehydes. The reaction scope includes ortho-, meta-, and para-substituted benzaldehyde derivatives with a range of electron-donating and -withdrawing groups as well as branched and unbranched aliphatic aldehydes. Catalytic loadings as low as 5 mol % give excellent yields in these reactions (up to 99%).

Scheme 2. Preparation of bis(amino)cyclopropenium salts 1 and 3.

A bis(amino)cyclopropenylidene (BAC) catalyzed aza-benzoin reaction between aldehydes and phosphinoyl imines has been developed. The reaction is general with a wide range of aromatic aldehydes and aromatic imines. The reaction displays excellent chemoselectivity favoring aza-benzoin products over homobenzoin products.

Two new carbon-rich macrocycles (radiaannulenes) have been synthesized, and they possess an unsaturated carbon framework that is intermediate between that of linearly-conjugated dehydrobenzannulenes and cross-conjugated expanded radialenes.

Als Alternative zu N‐heterocyclischen Carbenen wurden Bis(amino)cyclopropenylidene (BACs) untersucht. Diese Organokatalysatoren zeigen in der Stetter‐Reaktion gegenüber den weithin genutzten Thiazolylidenen und Triazolylidenen einige Vorteile. Außerdem vermitteln sie ausgedehnte Umpolungen von Enalen, und chirale Analoga für enantioselektive Katalysen sind leicht zugänglich.