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The Applications of Bifunctional Amine-thioureas Bearing Multiple Hydrogen Bonding Donors in Asymmetric Reactions

Author: DongXiuQin
Tutor: WangChunJiang
School: Wuhan University
Course: Organic Chemistry
Keywords: Asymmetric organocatalysis Multiple hydrogen bonds Tertiary amine-thiourea Nitro-Mannich reaction Michael addition
CLC: O643.3
Type: PhD thesis
Year: 2012
Downloads: 67
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Abstract


In recent years, much attention was paid to chiral thiourea catalysts owing to their uniquecatalytic effects. Many novel and effective chiral thiourea catalysts were designed andsynthesized, chiral amine-thiourea was one of the most important organocatalysts. It wassuccessfully applied into a lot of asymmetric reactions, such as Michael addition, Henryreaction, Strecker reaction, Baylis-Hillman reaction, Diels-Alder reaction. Chiral bifunctionalamine-thiourea catalysts bearing multiple hydrogen bonding donors were independentlydeveloped by our group, and they were made application into many asymmetric reactions, myresearch contents were as followed:1. A series of chiral bifunctional amine-thiourea catalysts bearing multiple hydrogenbonding donors were successfully applied into asymmetric nitro-Mannich reactions, thecatalyst I-d bearing two electron-withdrawing CF3groups on the aromatic ring ofsulfonamide NHSO2Ar emerged as the most effective catalyst. A variety of aryl N-Bocaldimines reacted with nitromethane smoothly to afford the corresponding products in highyields (85-99%) and excellent enantioselectivities (96-99%ee). Moreover, the poor reactiveand challenging alkyl N-Boc aldimines also obtained good results, the enantioselectivity wasup to98%ee. Indeed, other nitroalkanes and various N-Boc aldimines have proven to beexcellent substrates with respect to diastereo-/enantioselectivity and reactivity, thecorresponding products with two contiguous stereogenic centers were obtained in high yieldsand excellent diastereo-/enantioselectivities (93:7-99:1dr,96-99%ee).2. A highly diastereoselective and enantioselective Michael addition of nitroalkanes tonitroolefns has been achieved by chiral bifunctional amine-thiourea catalyst I-d. Thiscatalytic system proceeded well over a broad scope of substrates, furnishing various1,3-dinitro compounds in high diastereoselectivities (up to98:2dr) and excellentenantioselectivities (up to99%ee).3. We have developed the frst asymmetric Michael addition of-aryl cyclopentanonesand nitroolefns catalyzed by bifunctional amine-thiourea catalyst I-d. This catalytic systemperformed well over a broad scope of substrates and provided a series of the desired adductscontaining adjacent quaternary and tertiary stereogenic centers with excellentdiastereoselectivities (>99:1dr) and high enantioselectivities (90-96%ee), and it also realizedthe asymmetric Michael addition of-phenyl cyclohexanone and nitroolefn for the first time.The subsequent transformations led to expedient preparation of synthetically useful cyclicimine, nitrone and fused pyrrolidine.4. We first successfully developed the highly efficient asymmetric sulfa-Michael addition of thiols to ethyl4,4,4-trifluorocrotonate and4,4,4-trifluorocrotonamide catalyzed bybifunctional amine-thiourea catalyst I-d. They can be served as general methods for the directconstruction of chiral building blocks bearing a unique trifluoromethyl group and a sulfuratom at the stereogenic carbon center. And different configurational products can be easilyobtained through these sulfa-Michael additions. The products were efficiently hydrolyzed togive the key intermediate in the preparation of the potent inhibitor of MMP-3(stromelysin-1),-trifluoromethyl-sulfone hydroxamate.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic
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