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.
O–H and S–H insertion reactions of aryl- and diazo-substituted esters. Hydrogen-bond-donor catalysts enable a variety of formal insertion reactions of diazo compounds. The role of the catalyst in the reaction system may vary depending on several factors, including the nucleophilicity of the diazo compound and the acidity of the insertion partner. Ureas and phosphoric acid derivatives can offer complementary
Internal Lewis acid assisted ureas: tunable hydrogen bond donor catalysts
作者:David M. Nickerson、Veronica V. Angeles、Tyler J. Auvil、Sonia S. So、Anita E. Mattson
DOI:10.1039/c2cc37073e
日期:——
The strategic incorporation of internal Lewis acids onto urea scaffolds gives rise to a family of tunable hydrogenbond 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.
Arylation of Diazoesters by a Transient NH Insertion Organocascade
作者:Tyler J. Auvil、Sonia S. So、Anita E. Mattson
DOI:10.1002/anie.201304921
日期:2013.10.18
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 transientNHinsertion process.
Boronate Urea Activation of Nitrocyclopropane Carboxylates
作者:Sonia S. So、Tyler J. Auvil、Victoria J. Garza、Anita E. Mattson
DOI:10.1021/ol202873d
日期:2012.1.20
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.