The strategic incorporation of internal Lewis acids onto urea scaffolds gives rise to a family of tunable hydrogen bond donor catalysts. The nature of the Lewis acid and associated ligands affects the urea polarization, acidity, and activity in reactions of nitrocyclopropane carboxylates and nitrodiazoesters.

Boronate ureas are introduced as a new class of noncovalent catalysts for conjugate addition reactions with enhanced activity. Through intramolecular coordination of the urea functionality to a strategically placed Lewis acid, rate enhancements up to 10 times that of more conventional urea catalysts are observed. The tunable nature of boronate ureas is a particularly attractive feature and enables the rational design of catalysts for optimal performance, in terms of both activity and stereocontrol, in new bond-forming processes.

Boronate ureas operate as catalysts for the activation of nitrocyclopropane carboxylates in nucleophilic ring-opening reactions. A variety of amines were found to open the urea-activated nitrocyclopropane carboxylates, generating highly useful nitro ester building blocks in good yields. Standard manipulations allow access to a wide range of valuable compounds from the ring-opened products with direct applications in bioactive target synthesis.

Highly functionalized oxazinanes are efficiently prepared through urea-catalyzed formal [3 + 3] cycloaddition reactions of nitrones and nitrocyclopropane carboxylates. The reaction system is general with respect to both the nitrocyclopropane carboxylates and nitrones enabling the preparation of a large family of oxazinanes, typically in high yield. This method affords access to enantioenriched oxazinane products through chirality transfer from enantioenriched nitrocyclopropane carboxylates.

It takes two: A unique organocatalyzed cascade for the unsymmetric double arylation of α-nitrodiazoesters is described. This organocascade features the strategic use of carbene-activating anilines in conjunction with a urea catalyst, thus allowing for the synthesis of pharmaceutically attractive α-diarylesters through a transient NH insertion process.