Eric C Hansen

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Sulfamides, together with their simpler sulfonamide analogs, are common functional groups in a significant number of biologically active compounds. This is partly due to their unique electronic structure and conformational behavior, which mimics the tetrahedral intermediate involved in many proteases, esterases, and related enzymes. Here, the origin of(More)
Enyne metathesis is a powerful carbon-carbon bond-forming reaction to generate 1,3-dienes from an alkyne and an alkene. Different from the diene and diyne metathesis, the enyne metathesis suffers from both regio- and stereoselectivity problems, yet there is no general solution to these problems. This Account briefly describes the evolution of various new(More)
Medical imaging is routine in the diagnosis and staging of a wide range of medical conditions. In particular, magnetic resonance imaging (MRI) is critical for visualizing soft tissue and organs, with over 60 million MRI procedures performed each year worldwide. About one-third of these procedures are contrast-enhanced MRI, and gadolinium-based contrast(More)
Macrocyclic 1,3-dienes of a variety of ring sizes are formed in good yield via enyne metathesis. Both endo- and exo-products are observed depending on the size of the macrocycle. In general, 10-membered rings and smaller give exo-products, while 12-membered rings and larger give endo-products. The endo/exo selectivity and the E/Z ratio of the diene products(More)
Ligands are essential for controlling the reactivity and selectivity of reactions catalysed by transition metals. Access to large phosphine ligand libraries has become an essential tool for the application of metal-catalysed reactions industrially, but these existing libraries are not well suited to new catalytic methods based on non-precious metals (for(More)
A concise, asymmetric synthesis of a smoothened receptor inhibitor (1) is described. The synthesis features an enzymatic transamination with concurrent dynamic kinetic resolution (DKR) of a 4-piperidone (4) to establish the two stereogenic centers required in a single step. This efficient reaction affords the desired anti amine (3) in >10:1 dr and >99% ee.(More)
Despite their importance, the synthesis of alkylated heterocycles from the cross-coupling of Lewis basic nitrogen heteroaryl halides with alkyl halides remains a challenge. We report here a general solution to this challenge enabled by a new collection of ligands based around 2-pyridyl-N-cyanocarboxamidine and 2-pyridylcarboxamidine cores. Both primary and(More)
Photolysis of 1-(3-alkynoxy)-9,10-anthraquinones in deoxygenated methanol leads to moderate yields (35-45%) of 3-alkynals along with the unexpected formation of diacetals. Reaction of these 3-alkynals with Grignard and Wittig reagents occurs nearly quantitatively without rearrangement to their 2,3-dienal isomers.